Sound Practices Mailing List Files - Volume 2
=========================================================================
From: "Danielak, Robert M" <robert.m.danielak@lmco.com>
Subject: [JN] P-12 jensens
Date: Fri, 06 Aug 1999 11:03:55 -0400
Source: Sound Digest Archive v02.n226
joe wrote:
> My advice: Try a P-12 Jensen with a nice hard cone, add a tweeter if
> necessary.
>
> Joe
>
my question:
are these the same as was used in old guitar amps
jensen "special design"
i have a pair of p-12-n, i believe
may have the suffix screwed up
maybe p12-q ???
(according to the gerald weber guitar amp book
the ones i have are one notch from the
"top of the line" model...)
i had (ever distant) plans of building a pair of
guitar amps with them.
one for me and one for my brother...
would these be candidates for some sort of
almost-full-range stereo speaks...
the efficiency is something near 100db/w/m
if i recall correctly.
these are apparently being re-issued.
i think antique electronics
(www.tubesandmore.com)
is a distributer.
so what did you have in mind, joe?
bob.d.
=========================================================================
From: "Henry Platt" <hnplatt@massed.net>
Subject: Re: [JN] P-12 jensens
Date: Fri, 06 Aug 1999 12:40:46 -0700
Source: Sound Digest Archive v02.n226
Hi all.
Isn't the P12 the permanent magnet version of the Field coil Jensen A12?
What type of box should one use for these?
Henry
- ----------
>From: "Danielak, Robert M" <robert.m.danielak@lmco.com>
>To: sound@io.com
>Subject: [JN] P-12 jensens
>Date: Fri, Aug 6, 1999, 8:03 AM
>
> joe wrote:
>
>> My advice: Try a P-12 Jensen with a nice hard cone, add a tweeter if
>> necessary.
>>
>> Joe
>>
> my question:
>
> are these the same as was used in old guitar amps
>
> jensen "special design"
>
> i have a pair of p-12-n, i believe
>
> may have the suffix screwed up
>
> maybe p12-q ???
>
> (according to the gerald weber guitar amp book
> the ones i have are one notch from the
> "top of the line" model...)
>
> i had (ever distant) plans of building a pair of
> guitar amps with them.
> one for me and one for my brother...
>
> would these be candidates for some sort of
> almost-full-range stereo speaks...
>
> the efficiency is something near 100db/w/m
> if i recall correctly.
>
> these are apparently being re-issued.
> i think antique electronics
> (www.tubesandmore.com)
> is a distributer.
>
> so what did you have in mind, joe?
>
> bob.d.
>
=========================================================================
From: Joe Roberts <jroberts@io.com>
Subject: Re: [JN] P-12 jensens
Date: Fri, 06 Aug 1999 13:23:40 +0000
Source: Sound Digest Archive v02.n227
> are these the same as was used in old guitar amps
>
> jensen "special design"
>
> i have a pair of p-12-n, i believe
>
Yep, that's them. Sound pretty good. Try 'em out.
Joe
=========================================================================
From: "J. Gordon Rankin" <waudio@cinti.net>
Subject: Re: [JN] P-12 jensens
Date: Fri, 6 Aug 99 17:58:26 -0400
Source: Sound Digest Archive v02.n227
Gang,
If anyone is interested in a pair of A12-PM Jensen, these are the Alnico
version.
I have a pair of nice ones, trades are welcome!
Gordon
=======> Wavelength Audio <=======
mailto:waudio@cinti.net
http://www.WavelengthAudio.com
ph.fx. 513-271-4186 USA
=========================================================================
From: davidbarnett@aristotle.net (David Barnett)
Subject: Re: [JN] P-12 jensens
Date: Sat, 07 Aug 1999 00:26:48 GMT
Source: Sound Digest Archive v02.n227
On Fri, 06 Aug 1999 13:23:40 +0000, Joe Roberts <jroberts@io.com>
wrote:
>> jensen "special design"
>>
>> i have a pair of p-12-n, i believe
>>
>Yep, that's them. Sound pretty good. Try 'em out.
Have you tried the Weber VST copies of the old Jensen guitar speakers,
or the new Jensen reissues?
- --dnb
=========================================================================
From: "leamare" <leamare@vislink.it>
Subject: [JN] Pacific Audio line tranformer opinions?
Date: Wed, 27 Jan 1999 18:35:53 +0100
Source: Sound Digest Archive v02.n014
Hello,
I read about the Pacific Audio L106 line transformer, sold by La Maison de
l'Audiophile.
It consists of a transformer which replaces the line preamp; overall gain
is said to be 12 db.
Anyone tried it or any other comparable unit?
Opinions?
Sunny regards from Italy (eheheheh)
Armando
=========================================================================
From: "Cameron Brook" <cambrook@cyllene.uwa.edu.au>
Subject: [JN] pair ALTEC "288- 16G"
Date: Mon, 6 Dec 1999 09:08:09 +0800
Source: Sound Digest Archive v02.n354
some Joes might be interested in these,
no connection with seller etc etc
http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=214265396
=========================================================================
From: "Daniel J. Marshall" <danmarshall@worldnet.att.net>
Subject: [JN] Pair of 280 Wztt Hammond Outputs on eBay
Date: Tue, 08 Feb 2000 20:46:12 -0800
Source: Sound Digest Archive v02.n440
In case anyone is interested. I have no connection with this, just
recall some big-amp talk here recently and thought I would pass it on.
One more day to go, current bid is $172.50 for the pair. AES price is
$205.50 each.
http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=252440690
=========================================================================
From: Dan Kerl <dlkerl@ro.com>
Subject: Re: [JN] Pair of 280 Wztt Hammond Outputs on eBay
Date: Wed, 09 Feb 2000 08:44:30 -0600
Source: Sound Digest Archive v02.n440
"Daniel J. Marshall" wrote:
>
> In case anyone is interested. I have no connection with this, just
> recall some big-amp talk here recently and thought I would pass it on.
> One more day to go, current bid is $172.50 for the pair. AES price is
> $205.50 each.
>
> http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=252440690
Also, from
http://www.angela.com/catalog/transformers/Hammond_Transformers.html
1650W 280W, 1900 ct, 4/8/16 ohm, 6L6GC, 5881, EL34, 6550B, KT88, SALE!!!
$148!!
Might make a good SVT clone.
- --
Dan Kerl
dlkerl@ro.com
=========================================================================
From: Ken Gilbert <ride5000@ride.ri.net>
Subject: Re: [JN] Pair of 280 Wztt Hammond Outputs on eBay
Date: Wed, 09 Feb 2000 17:50:08 -0500
Source: Sound Digest Archive v02.n441
>Also, from
>http://www.angela.com/catalog/transformers/Hammond_Transformers.html
>
>1650W 280W, 1900 ct, 4/8/16 ohm, 6L6GC, 5881, EL34, 6550B, KT88, SALE!!!
>$148!!
>
>Might make a good SVT clone.
Dan, et al,
i've got two of them in a big ass guitar amp sitting outside in my garage... i
just threw down 200 bucks on that auction and was immediately outbid (proxy).
TWO of them will make an SVT _killer_. that price from angela is damned good.
i picked mine up a year ago on rat from a guy in canada... he had two
consecutively serial-numbered units, which was nice, for $300, which was a
steal at the time. i don't really have the discretionary income to give that
high bidder a run for his money... figure on 50 for the shipping, so i'd go as
high as 250, but only if i really wanted them!
ken
=========================================================================
From: Rick Francis <rfrancis@glasscity.net>
Subject: [JN] Pair of OPTs from DuKane PP 6CD6 50-watt amps
Date: Thu, 02 Sep 1999 07:28:07 -0400
Source: Sound Digest Archive v02.n269
The amps were cannibalized for the PTs, but I have this pair of OPTs for
someone. They were rusty, but I cleaned them up, used Rustoleum primer,
then used Rustoleum black enamel. I think they look pretty good. Lots of
secondary taps, including 70v. No UL taps, sorry.
I'll measure dimensions if anyone wants, but be assured they are fairly
hefty -- the size you would expect for EL-34s, 7591, etc. I think they
would be great for a couple of guitar amps, or a budget stereo amp. How
about $25/pair plus shipping, and I'll throw in a copy of the original
schematic? Or will swap for something interesting.
Rick
=========================================================================
From: Rick Francis <rfrancis@glasscity.net>
Subject: [JN] Pair plate transformers on ebay
Date: Tue, 28 Dec 1999 10:20:11 -0500
Source: Sound Digest Archive v02.n373
There's a pair of plate transformers on ebay, ending today:
http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=224594048
Look at the picture and you'll see more info than is given in the
description. It's 1120 vct, plus another winding. Not high current, but
might work great for a minimalist 845 amp. If I didn't have a pile of iron
in my basement, I'd probably get them.
Rick
=========================================================================
From: Scott Grammer <tubedude@sunnetusa.net>
Subject: [JN] Panasonic DVD
Date: Fri, 26 Nov 1999 20:04:09 -0500
Source: Sound Digest Archive v02.n346
I just heard that Panasonic is marketing a DVD player billed as a "DVD
Audio Player that also plays movies". In other words, they are
emphasizing the audio and it just happens to play movies. It will
support sampling rates up to 192kHz, and is 24 bit, of course. I'll find
out the model number and whatever else I can and report back.
Scott.
- --
"To save every cog and wheel is the first
precaution of intelligent tinkering." -Aldo Leopold.
What if there were no hypothetical questions?
=========================================================================
From: Jan Nielsen <sound@image.dk>
Subject: Re: [JN] Panasonic DVD
Date: Sat, 27 Nov 1999 22:37:05 +0100
Source: Sound Digest Archive v02.n346
Hi Scot,
This would be the Technics DVD A10.
I had it home for a short review - only one week. The price here in Denmark
is approx. 11.000 DKR.
Only one DVD-Audio Disc was supplied and the quality was a bit mixed. The
top was OK but at bit from the best - i.e. high end CD's like Mark Levinson
and Accuphase. The most impressive was the low end, which is tight with a
lot of weight and dynamics. Picture quality and surround-modes (built in DTS
konverter!) is the typical high quality you get from the best DVD-players.
It's still too soon to make any conclusions. The future will show (as the
CD-media has) what the DVD-Audio standard can give us ind extra resoultion
and "analog-like" quality.
Regards,
Jan Nielsen
Scott Grammer wrote:
> I just heard that Panasonic is marketing a DVD player billed as a "DVD
> Audio Player that also plays movies". In other words, they are
> emphasizing the audio and it just happens to play movies. It will
> support sampling rates up to 192kHz, and is 24 bit, of course. I'll find
> out the model number and whatever else I can and report back.
>
> Scott.
> --
> "To save every cog and wheel is the first
> precaution of intelligent tinkering." -Aldo Leopold.
>
> What if there were no hypothetical questions?
=========================================================================
From: "J. Gordon Rankin" <waudio@cinti.net>
Subject: Re: [JN] Panasonic DVD
Date: Mon, 29 Nov 99 10:57:41 -0500
Source: Sound Digest Archive v02.n347
>I just heard that Panasonic is marketing a DVD player billed as a "DVD
>Audio Player that also plays movies". In other words, they are
>emphasizing the audio and it just happens to play movies. It will
>support sampling rates up to 192kHz, and is 24 bit, of course. I'll find
>out the model number and whatever else I can and report back.
Scott,
Supposedly the Technics and Panasonic are the first two fully released Audio grade DVD's.
The Technics unit is suppose to be real nice!
~~~~ From Panasonic ~~~~~
Thank you for your e-mail inquiry concerning Panasonic DVD products.
Please review the latest press release on DVD audio. These units should be
available late 99, early 2000. There is only preliminary information
available.
SECAUCUS, NJ (July 27, 1999) - Panasonic Consumer Electronics Company
(PCEC), the first company to show DVD-Audio players in the United States
earlier this year, affirms its commitment to this new and exciting audio
medium by being the first to announce delivery timing and suggested pricing
for two models, the Panasonic-brand DVD-A7 and the Technics DVD-A10.
Beginning this October, both models will be shipped to dealers nationwide.
The Panasonic DVD-A7 has a manufacturer's suggested retail price of $999.95.
The Technics DVD-A10 carries a manufacturer's suggested retail price of
$1,199.95.
These next generation audio players can be easily incorporated into your
home entertainment system. But while the players will accept and play
conventional CDs, future DVD-Audio discs will be reproduced with far greater
fidelity then presently available. And DVD-Audio is capable of much more.
Attached to a home entertainment's television or projection TV, a DVD-Audio
player can also reproduce video: graphics, text, music videos, and more can
be shown. Additionally, since the player is compatible with DVD Video discs,
your favorite DVD movies can be played as well-along with up to 5.1 channels
of Dolby Digital® and DTS® multi-channel sound. Want more? Future DVD-Audio
discs could even contain URL addresses for instant access to relevant Web
sites as you listen-or watch-a DVD-Audio disc.
"DVD-Audio not only far exceeds the audio quality of conventional CD
reproduction, but provides new enhancements that can combine listening with
a truly interactive experience," says Gene Kelsey, vice president and
general manager of Panasonic's Audio Group. "A DVD-Audio/Video player will
be the cornerstone component of all home entertainment systems of the near
future."
The true acceptance of a new audio format means equal enthusiasm from the
software industry as well. And that is already happening. "Universal Music
Group is looking forward to supporting the first new audiophile standard
since the introduction of CDs almost twenty years ago," says Lisa Farris,
vice president of marketing for Universal Music Group - eCAT. "By providing
recording artists with an expanded aural palette, DVD-Audio's better than CD
quality stereo and multi-channel surround sound showcases a whole new
listening experience for the consumer. Universal Music Group is preparing
releases from a wide range of artists covering every genre in conjunction
with the launch of the DVD-Audio player."
Conforming to the newly established DVD-Audio standard, and containing an
encryption system to prevent unauthorized disc duplication, DVD-Audio takes
advantage of the digital technology originally developed for DVD-Video. It
uses the advanced format's vast data storage potential to deliver astounding
sound enriched with the nuance, warmth and subtle overtones of a live
musical performance.
To accomplish this, 2-channel DVD-Audio uses a sampling frequency of 192kHz
- - more than four times that of CD - to extend the playback high-frequency
response to an incredible 96kHz. The higher frequency reproduction gives
live instruments their timbre or resonance, which is often lost on a compact
disc. The crash of cymbals, for instance, produces frequencies well above
20kHz - inaudible to the ear but important to retaining the instrument's
distinct expression and the integrity of the music.
In addition, a new Digital-To-Analog Converter (DAC), based on MASH*
technology and refined by Matsushita for 192kHz/24-bit DVD-Audio use, gives
these players the ability to distinguish levels of sound using 24-bit
quantization (vs. 16-bit maximum for CD). This reduces background noise to
imperceptible levels. The new DAC is also combined with a DIGITAL RE-MASTER
PROCESSING circuit, which uses audio dithering techniques to increase the
frequency response and dynamic range of conventional CDs as well.
DVD-Audio is fully multi-channel sound compatible and uses PCM (Pulse Code
Modulation) for all channels, presenting a new level of multi-channel sound
quality, unprecedented realism in ambience reproduction, and the potential
to create radically different sound spaces. Incorporating both Dolby
Digital® and DTS® decoders, the players can decode music and soundtracks
recorded in up to 5.1 channels (including a subwoofer) to give listeners the
ambience and enveloping effect of a live performance.
Also like its video cousin, DVD-Audio is capable of single- or dual-layer
capacity on one or both disc sides. At its highest rate (192kHz/24-bit
2-channel PCM), the format can store 74 minutes of music on a single-side of
a single-layer disc. At lower recorded rates, that figure can balloon to 400
minutes - or more than 6-1/2 hours of music at CD equivalent quality.
Additionally, the format uses a technique called Lossless Coding, which is a
compression system that removes redundancies in the audio signal to enhance
recording capacity and enable virtually perfect reconstruction of the
original signal. Using Lossless Coding, up to 74 minutes of 96kHz/24-bit/6
channel recordings can be squeezed onto one side of the DVD-Audio disc. An 8
cm disc is also an option for music singles or other short programs.
The extensive storage space not only permits extended-range audio, but full
MPEG-2 video, still images, and text as well, to fuse pictures and sounds
into a new world of entertainment interactivity. When connected to a
television or computer monitor for example, and depending on disc content,
DVD-Audio players allow "listeners" to watch music videos with unparalleled
audio and DVD-quality video, view "photo albums" of band members, or read
track titles, song lyrics and liner notes on the screen. Internet URL
addresses embedded in the disc can also link listeners directly to relevant
Web sites when the player is connected to a PC. And, visual menus can help
users easily navigate all the offerings on a disc.
While the Panasonic DVD-A7 provides extraordinary audio and video quality,
the Technics DVD-A10 is a step above and designed to address the needs of
discriminating audiophiles. For example, to complete an uncompromising
design, the audio power supply in the DVD-A10 incorporates a system called
Advanced Virtual Battery Operation. Using a capacitor to supply its charged
power to the audio reproduction circuitry, the technique simulates a battery
(pure source of DC current) to virtually eliminate power supply "noise" for
faithful reproduction of even the smallest signal information. Additionally,
an R-Core transformer, which has a rounded shape to help minimize leakage
flux and noise, replaces the conventional transformers with their
squared-off corners and uneven flux patterns. And TA-KE II electrolytic
capacitors are used throughout for better mid-high frequency response with
lower distortion. Even the cabinetry is impressive: a sleek champagne gold
component with a special vibration damping base.
"DVD-Audio is about to unleash an entirely new revolution in what we now
simply call home audio," says Kelsey. "It will be an attack on both our
aural and visual senses, taking the performer yet another giant step closer
into our living rooms."
Panasonic and Technics consumer electronics products are marketed in the
United States by Panasonic Consumer Electronics Company (PCEC), a division
of Matsushita Electric Corporation of America (MECA). MECA is the principal
North American subsidiary of Matsushita Electric Industrial Co., Ltd.,
(NYSE: MC) of Japan, one of the world's largest producers of electronic and
electric products and a key developer of technology for DVD, mobile DVD,
DVD-ROM, DVD-RAM and DVD Audio. Prices are in U.S. currency. (Consumers
seeking more information on the company's products can call Panasonic's
Customer Call Center at 800-211-PANA or access Panasonic's home page at
www.panasonic.com <http://www.panasonic.com> . or www.technicsusa.com
<http://www.technicsusa.com> . Media interested in Panasonic or Technics
press releases can gain information via the Panasonic Web site or through
New Directions Public Relations' toll-free fax-back system at 888-734-7490.)
Specifications and design subject to change without notice.
*Matsushita Electric Industrial Co., Ltd., incorporates MASH (multi-stage
noise shaping technology) in its products under technical license from NTT.
Dolby Digital® is a trademark of Dolby Laboratories Licensing Corporation.
DTS® is a trademark of Digital Theater Systems, Inc.
Down load the press release
MAC: DVD-Audio-31.txt.sea.hqx | PC: DVD-Audio-31.zip
BACK
Copyright ©1998 Matsushita Electric Corporation of America. All rights
reserved.
If we can further assist you other Panasonic, Technics or Quasar products;
please contact the Panasonic Customer Call Center (1-800-211-PANA). For your
convenience, the call center is open from 9:00 am to 9:00 p.m. (est.;
Mon-Fri) and from 9:00 am to 7:00 p.m. (est.; Sat/Sun).
Best regards,
Panasonic Customer Call Center
~~~
Gordon
=======> Wavelength Audio <=======
mailto:waudio@cinti.net
http://www.WavelengthAudio.com
ph.fx. 513-271-4186 USA
=========================================================================
From: Nicholas McKinney <nick@lambdacoustics.com>
Subject: Re: [JN] Panasonic DVD
Date: Mon, 29 Nov 1999 13:35:36 -0500
Source: Sound Digest Archive v02.n348
At 10:57 AM 11/29/99 -0500, J. Gordon Rankin wrote:
>Supposedly the Technics and Panasonic are the first two fully released Audio
>grade DVD's.
>
>The Technics unit is suppose to be real nice!
Hi Folks, I didn't see it anywhere, but do they play CDR discs?
Very important option for me at least, most DVD players don't allow for this.
Nick
Nicholas McKinney
Lambda Acoustics Inc.
www.lambdacoustics.com
www.onelist.com/community/LambdaDrivers
=========================================================================
From: Scott Grammer <tubedude@sunnetusa.net>
Subject: Re: [JN] Panasonic DVD
Date: Mon, 29 Nov 1999 22:33:57 -0500
Source: Sound Digest Archive v02.n348
Nicholas McKinney wrote:
(snip)
> Hi Folks, I didn't see it anywhere, but do they play CDR discs?
>
> Very important option for me at least, most DVD players don't allow for this.
>
> Nick
Nick:
You have to be careful putting CDR's in a DVD player. DVD players use a
much more powerful laser than CD players, and they can erase CDR's!
Scott.
- --
"To save every cog and wheel is the first
precaution of intelligent tinkering." -Aldo Leopold.
What if there were no hypothetical questions?
=========================================================================
From: "Multi-Volti Devices" <multi-volti@softhouse.com>
Subject: [JN] paper in oil caps
Date: Wed, 12 May 1999 23:47:20 -0400
Source: Sound Digest Archive v02.n142
Hello:
Not sure if I already asked this...
I have some nos 0.1 uF 450 vac paper in oil in ceramic tube/axial lead caps
(estimated DC V 1100+). (Matsushita Industrial)
I have given some to some field testers/listeners and so far they are very
happy with them in PP and SE applications.
I have had some inquiry about selling additional ones, but don't know what
they're worth. If they're not worth much, I'll keep them for my own designs.
If they're worth anything, I might unload some to fund other audio project
expenses.
Thanks
Murray
=========================================================================
From: Ishmael349@aol.com
Subject: [JN] Re:paper voice coils
Date: Mon, 25 Jan 1999 10:16:34 EST
Source: Sound Digest Archive v02.n011
I actually built that speaker. Wish I could find the phone number of the guy
who I gave it to, he was a recording engineer and says he, "loves it" and is
"still using it". I built mine out of MDF and I remember playing with some
stuffing. I bet it sounds good. Better yet, look for drivers with PAPER
voice coils. The sound character of a driver is (in my opinion) influenced by
the material of the voice coil than the cone material. Paper, with natural
glues, is (for me, and Kondo) the best. Remember everything sounds like what
it is made of. Try it!
Herb
=========================================================================
From: Mindaugas <mk@is.lt>
Subject: [JN] Paper vs metalized foil
Date: Mon, 1 Mar 1999 10:00:45 +0200 (EET)
Source: Sound Digest Archive v02.n064
Hello all.
I found in the basement old vintage tube amp where all caps are old (motor
run) paper in oil caps. Does it makes sense to replace them all with the
metalized polyprophylene foil Wima caps (I am considering ordering these)?
Any thoughts would be appreciated.
Mindaugas
mk@is.lt
=========================================================================
From: Dan Marshall <mdaniel7@uswest.net>
Subject: Re: [JN] Papst Motor Puzzle
Date: Tue, 15 Aug 2000 09:30:45 +0000
Source: Sound Digest Archive v02.n629
It sounds like what you have is a three phase motor. It ought to run in
single phase with a cap though, after a fashion, and, assuming it is a
three-phase motor, it would not matter what combination of leads you
used, any combo that caused it to turn in the desired direction of
rotation would be equivalent to any other connection. As to why it
doesn't run, I couldn't say. Are you sure it is rated for 115 volts
line voltage. Three phase would be a preferable driving source.
Three-phase motors will run on single phase with any two leads
energized, if you give it a spin to get it started. The cap ought to
take care of this though, as long is the motor is lightly loaded. Try
winding a string around the shaft and give it a brisk spin when it is
switched on (with two terminals energized and see if it will run.
DM
Kalman Rubinson wrote:
>
> Having found what appears to be a great drive for
> my turntable project, I am stymied by it.
>
> I have two samples of a NOS Papst motor which is supposed to
> be an AC synchronous motor built for use as a capstan drive
> in studio tape recorders like Ampex and Tascam. There are
> three leads and the following printing on each:
> PAPST-MOTOREN KG
> 9018032029
> HSKZ 32.80-12-135D
> 115V 60Hz 6uF Marz.77
>
> The rotor turns freely indicating that there are no bearing
> problems. Connecting the AC to BLK and RED and the 6uF cap
> between RED and OR, the motor buzzes gently but will not
> turn on its own. Other connection arrangements give similar
> outcome.
>
> Measurements give 165ohms between any(!) two leads. This
> holds for both samples. (I'd have expected one measurement
> to be the sum of the other two on a typical synchronous
> motor.)
>
> The literature that Papst has dredged up from their archives
> is puzzling since it refers to this model but with much
> lower capacitance (and much more German text) than printed
> on the motors.
>
> Any ideas?
>
> Kal
=========================================================================
From: Kalman Rubinson <kr4@is2.nyu.edu>
Subject: [JN] Papst Motor Puzzle
Date: Tue, 15 Aug 2000 11:38:01 -0400 (EDT)
Source: Sound Digest Archive v02.n629
Having found what appears to be a great drive for
my turntable project, I am stymied by it.
I have two samples of a NOS Papst motor which is supposed to
be an AC synchronous motor built for use as a capstan drive
in studio tape recorders like Ampex and Tascam. There are
three leads and the following printing on each:
PAPST-MOTOREN KG
9018032029
HSKZ 32.80-12-135D
115V 60Hz 6uF Marz.77
The rotor turns freely indicating that there are no bearing
problems. Connecting the AC to BLK and RED and the 6uF cap
between RED and OR, the motor buzzes gently but will not
turn on its own. Other connection arrangements give similar
outcome.
Measurements give 165ohms between any(!) two leads. This
holds for both samples. (I'd have expected one measurement
to be the sum of the other two on a typical synchronous
motor.)
The literature that Papst has dredged up from their archives
is puzzling since it refers to this model but with much
lower capacitance (and much more German text) than printed
on the motors.
Any ideas?
Kal
=========================================================================
From: Christian Rintelen <Christian@rintelen.ch>
Subject: Re: [JN] Papst Motor Puzzle
Date: Tue, 15 Aug 2000 18:12:53 +0200
Source: Sound Digest Archive v02.n629
This is a multi-part message in MIME format.
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Could it be that you have a 3 phase AC synchronous motor? (This was
often done on very hiqh quality motors - EMT also uses 3 phase
motors). Check out
http://www2.cds.ne.jp/~yogawa/emt930/emt930_CIRCUIT.gif - this
schematic shows how the EMT 3 phase motor is connected with a 1.5 uF
cap and a 2k pot for phase adjustment.
What does the "much more German text" say? I can probably help...
Christian
Kalman Rubinson wrote:
> Having found what appears to be a great drive for
> my turntable project, I am stymied by it.
>
> I have two samples of a NOS Papst motor which is supposed to
> be an AC synchronous motor built for use as a capstan drive
> in studio tape recorders like Ampex and Tascam. There are
> three leads and the following printing on each:
> PAPST-MOTOREN KG
> 9018032029
> HSKZ 32.80-12-135D
> 115V 60Hz 6uF Marz.77
>
> The rotor turns freely indicating that there are no bearing
> problems. Connecting the AC to BLK and RED and the 6uF cap
> between RED and OR, the motor buzzes gently but will not
> turn on its own. Other connection arrangements give similar
> outcome.
>
> Measurements give 165ohms between any(!) two leads. This
> holds for both samples. (I'd have expected one measurement
> to be the sum of the other two on a typical synchronous
> motor.)
>
> The literature that Papst has dredged up from their archives
> is puzzling since it refers to this model but with much
> lower capacitance (and much more German text) than printed
> on the motors.
>
> Any ideas?
>
> Kal
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=========================================================================
From: Kalman Rubinson <kr4@is2.nyu.edu>
Subject: [JN] Re: Papst motor puzzle
Date: Wed, 16 Aug 2000 21:07:12 -0400 (EDT)
Source: Sound Digest Archive v02.n630
Hooray! I got the motor running (got out on the
highway!) by using a 2 to 4 mfd cap, not the specified
6mfd cap. However, it must be a 3phase motor and running
it this way does not result in low vibration.
Any wisdom on triphase supplies? I have a few ideas.
Kal
=========================================================================
From: Ed Faulkner <efaulkne@wsunix.wsu.edu>
Subject: [JN] PA question
Date: Thu, 17 Jun 1999 10:18:13 -0700
Source: Sound Digest Archive v02.n181
I am assisting a department here at WSU again with their PA system (Altec
A5s) in a large multipurpos room. They are experiencing a slight delay in
the sound system and I would appreciate any input you people might have.
Recently they removed 70V line transformers and are driving the speakers
from a transistor amp with a maximum cable length of about 100 ft. Can some
cables create a delay line when used this way? The wire is nothing special,
two insulated conductors and a plenum grade sheath.
If anyone feels this question should not be on this list please let me
know. I no longer suscribe to other groups because of time limitations and
appreciate any assistance you may be able to provide. Please respond
directly to efaulkne@wsu.edu unless the information is usefull to the list.
_____________________________
Ed Faulkner \ through a child's eyes
CMT Supervisor \ sky is blue
Washington State University \ grass is green
Pullman, WA,99164 \ I want to see again
(509) 335-7566 \
efaulkne@wsu.edu \______________________
=========================================================================
From: Scott Grammer <tubedude@cdc.net>
Subject: Re: [JN] PA question
Date: Thu, 17 Jun 1999 16:31:17 -0400
Source: Sound Digest Archive v02.n181
Ed Faulkner wrote:
> I am assisting a department here at WSU again with their PA system (Altec
> A5s) in a large multipurpos room. They are experiencing a slight delay in
> the sound system and I would appreciate any input you people might have.
>
> Recently they removed 70V line transformers and are driving the speakers
> from a transistor amp with a maximum cable length of about 100 ft. Can some
> cables create a delay line when used this way? The wire is nothing special,
> two insulated conductors and a plenum grade sheath.
>
> (snip)
Ed:
When you say a "delay", do you mean an echo? Or is there some period of time
between when a sound reaches a microphone and the time it leaves a speaker?
No cable is going to create an audible delay. (OK, come on, somebody argue with
me. I know it's going to happen. Out with it.) If you have an echo, it is most
likely a reflection from the back wall of the auditorium. This is a common
problem, especially with auditoriums seating between 200 and 1,000 people. Only
serious sound deadening materials or, better yet, remodeling will cure that. If
you are experiencing a true delay, between the mic and speaker, then there is a
delay line (electronic) in the system somewhere. It may have been installed to
reduce feedback (I hope not) or to use for "echo effects". Find it and take it
out of line.
BTW, some active crossovers and equalizers have delay lines built in for time
alignment of speaker drivers. This may be where the delay line is hiding.
Good luck!
S.G.
- --
TubeDude's Webpage of Vacuum Tube Lore! http://www.cdc.net/~tubedude/
Smoke Free Youth! http://www.cdc.net/~tubedude/smokefreeyouth.html
The Price of Privacy. http://www.cdc.net/~tubedude/privacy.html
"The nice thing about standards is that you have so many to choose from."
-- Andrew S. Tanenbaum, _Computer Networks_, 2nd ed, p.254
=========================================================================
From: davidbarnett@aristotle.net (David Barnett)
Subject: Re: [JN] PA question
Date: Thu, 17 Jun 1999 19:12:51 GMT
Source: Sound Digest Archive v02.n181
On Thu, 17 Jun 1999 10:18:13 -0700, Ed Faulkner
<efaulkne@wsunix.wsu.edu> wrote:
>They are experiencing a slight delay in
>the sound system and I would appreciate any input you people might have.
This sounds more like a function of the room acoustics than a problem
with the system.
- --dnb
=========================================================================
From: davidbarnett@aristotle.net (David Barnett)
Subject: Re: [JN] PA question
Date: Fri, 18 Jun 1999 22:23:50 GMT
Source: Sound Digest Archive v02.n181
On Thu, 17 Jun 1999 10:18:13 -0700, Ed Faulkner
<efaulkne@wsunix.wsu.edu> wrote:
> They are experiencing a slight delay in
>the sound system and I would appreciate any input you people might have.
This is obviously a basic design flaw of the Altec A5. Get them to
buy a set of Peavey speakers, and I'll gladly come and haul off the
A5s for no charge.
- --dnb
=========================================================================
From: Scott Grammer <tubedude@cdc.net>
Subject: Re: [JN] PA question
Date: Fri, 18 Jun 1999 21:39:18 -0400
Source: Sound Digest Archive v02.n182
David Barnett wrote:
> (snip)
>
> This is obviously a basic design flaw of the Altec A5. Get them to
> buy a set of Peavey speakers, and I'll gladly come and haul off the
> A5s for no charge.
>
> --dnb
HA!
ROFLMAO!
S.G.
- --
TubeDude's Webpage of Vacuum Tube Lore! http://www.cdc.net/~tubedude/
Smoke Free Youth! http://www.cdc.net/~tubedude/smokefreeyouth.html
The Price of Privacy. http://www.cdc.net/~tubedude/privacy.html
"The nice thing about standards is that you have so many to choose from."
-- Andrew S. Tanenbaum, _Computer Networks_, 2nd ed, p.254
=========================================================================
From: Allen Wright <AllenVSE@compuserve.com>
Subject: [JN] Parafeed?
Date: Wed, 18 Oct 2000 05:56:29 -0400
Source: Sound Digest Archive v02.n696
Joes and Joette(s),
Re Parafeed:
I am not trying to be smart here - Parafeed is strongly recommended by some
serious heavy hitters, yet I have these conflicts:
a/ It is my understanding that one of the generally assumed "problems" with
push-pull topology is that without signal the OPT sits with zero flux
(assuming the DC standing currents are balanced) and that when some signal
arrives the OPT must swing through a quite non-linear segment of it's BH
curve before reaching a more optimum portion. And does this non-linear to
linear dance on every zero crossing transition of the signal. Yes?
b/ A (conventional) SE amp correctly matched to it's (air-gapped) OPT runs
a standing current that places it's operating condition right in the middle
of the most linear part of the BH curve area - and in normal operation
should never swing down (or up) as far as the curved portion the P-P amp
cannot advoid. Yes?
c/ And this standing current in the OPT is one of the theroretical
advantages of the SE topology - Yes?
d/ A single ended parafeed amp (normally) is is choke loaded and cap feeds
an OPT - which doesn't have/need an air gap because it doesn't carry any DC
current. Yes?
Question 1: Why then doesn't a parafeed amp suffer exactly the same "non
linearity" around the zero crossing point that P-P (supposedly) does?
Question 2: If it does have this non linear distortion due to the BH curve,
what are the theoretical advantages of parafeed that outweigh this and yet
are not possible in a PP design?
Very curious on these points...
Allen (VSE)
=========================================================================
From: "T. Loesch" <ezee_e@hotmail.com>
Subject: Re: [JN] Parafeed?
Date: Wed, 18 Oct 2000 10:22:25 GMT
Source: Sound Digest Archive v02.n696
Hi,
>c/ And this standing current in the OPT is one of the theroretical
>advantages of the SE topology - Yes?
Yes. Also remeber that there some serious energy stored in that primary
inductance of the OPT....
>Question 1: Why then doesn't a parafeed amp suffer exactly the same "non
>linearity" around the zero crossing point that P-P (supposedly) does?
But it does, unless you use OPT's with Permalloy or such in parafeed you
have the same problem in parafeed as in PP.
>Question 2: If it does have this non linear distortion due to the BH curve,
>what are the theoretical advantages of parafeed that outweigh this and yet
>are not possible in a PP design?
Non that I can see (or hear for that effect).
I commented before that IMHO much of the "improved bass" with parafeed is in
fact a resonance phenomenae between the way to small coupling Cap and the
involved inductances, leading to an EQ, to the tune of as much as 3 - 4db at
LF....
One advantage is that a smaller core can be used for the OPT and hence the
OPT will have better HF or be cheaper to make (take your pick). And the PSRR
is better in Parafeed, though it can be equalled in most circuits if we use
cancellation form the HT.
As said before, I cannot percieve either technical or audible advantages
from Parafeed, but there are economical ones....
Later T
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=========================================================================
From: TubeGarden@aol.com
Subject: Re: [JN] Parafeed?
Date: Wed, 18 Oct 2000 07:10:55 EDT
Source: Sound Digest Archive v02.n697
In a message dated 10/18/00 3:02:26 AM US Mountain Standard Time,
AllenVSE@compuserve.com writes:
> Question 1: Why then doesn't a parafeed amp suffer exactly the same "non
> linearity" around the zero crossing point that P-P (supposedly) does?
The DC is holding the choke at flux.
>
> Question 2: If it does have this non linear distortion due to the BH curve,
> what are the theoretical advantages of parafeed that outweigh this and yet
> are not possible in a PP design?
>
It doe not, only A/C passes the output transformer.
One may build a parafeed PP design and reap the benefits.
Whether they are to one's taste is another matter.
I found being able to seriously listen to a $20. output transformer a great
joy, others may be more jaded :)
Happy Ears!
Al B^}
=========================================================================
From: Roscoe Primrose <roscoe@aiko.com>
Subject: Re: [JN] Parafeed?
Date: Wed, 18 Oct 2000 09:18:07 -0400
Source: Sound Digest Archive v02.n697
TubeGarden@aol.com wrote:
>
> In a message dated 10/18/00 3:02:26 AM US Mountain Standard Time,
> AllenVSE@compuserve.com writes:
>
> > Question 1: Why then doesn't a parafeed amp suffer exactly the same "non
> > linearity" around the zero crossing point that P-P (supposedly) does?
>
> The DC is holding the choke at flux.
What, pray tell, does this have to do with the OPT non-linearity at the
zero crossing point?
>
> >
> > Question 2: If it does have this non linear distortion due to the BH curve,
> > what are the theoretical advantages of parafeed that outweigh this and yet
> > are not possible in a PP design?
> >
> It doe not, only A/C passes the output transformer.
Which is precisely why it DOES pass through a very non-linear potion of
the BH curve. If you look at the curves, one of the most non-linear
regions is near zero flux as the field polarity reverses.
Peace
- --
Roscoe Primrose -- mailto:roscoe@aiko.com --
http://www.aiko.com/roscoe
"Once in a while you get shown the light
In the strangest of places if you look at it right." Robert Hunter
"640K ought to be enough for anybody" , Bill Gates, 1981
=========================================================================
From: "Danielak, Robert M" <robert.m.danielak@lmco.com>
Subject: RE: [JN] Parafeed?
Date: Wed, 18 Oct 2000 10:58:36 -0400
Source: Sound Digest Archive v02.n697
hi folks,
i am a little confused.
i have heard a number of you say that in a conventional SE
OPT with DC bias, the flux swings thru the most linear portion
of the BH curve.
and that in a PP amp, it has to swing thru a more non-linear
portion of the BH curve.
i think i understand where you are going with this,
but i believe that this statement is fundamentally incorrect
or at least requires clarification.
from a steadt-state perspective,
the BH curve, ignoring hysteresis for the moment, is symmetrical about the
origin. including hysteresis, it is sort of a "mirror image" across the
origin.
so with a *symmetrical* exitation (such as a sine-wave)
a PP opt benefits from being able to swing over a wider
B and H level (-/- quadrant as well as +/+ quadrant).
there is no "zero-crossing" non-linearity as far as the BH curves are
concerned.
and also heep in mind (i think someone else already mentioned)
that in a SE OPT with DC bias, there is a "miniature" BH loop
that the signal follows - inside the major BH loop.
the zero crossing simply occurs about the new bias point.
however, we are not concerned with "steady-state" analyses
when we are talking about a dynamic excitation such as music!
just considering a transient analysis, for now, there is an effect
associated with the "initial magnitization" of the core.
it is assumed that the residual flux in the core is zero,
and the BH trajectory during the first transient begins at the origin. this
trajectory is usually shown as a non-linear path
to the "steady-state" BH curve. it looks like a diode curve
that eventually bends into an "S" to match the bend-over of the BH curve at
high B.
*this* is probably the effect that youse guru must be referring to.
you could imagine that this would repeat on every transient,
like a burst of sine, then rest, then another burst.
during the first sine, the trajectory would follow the "initial
magnetization" curve - at least for a while.
during the rest of the sines, the trajectory would follow the
"normal" BH curve - in a fairly linear fashion.
i suppose there is a comparable "decay" bach to the zero point
when the burst stops - this could be even worse effect [?!?].
real music is *much* more complicated than this simplification.
so who knows what is going on...
now i have to wonder. does this "initial magnetization" effect
go away when you apply a DC bias?
it is easy to assume that it does.
but i am not so sure.
or maybe it still occurs, but the trajectory eminates from the DC operating
point instead of the origin.
what makes the ZERO flux point so special
(as opposed to a particular DC operating point that has been
stable for an appreciable duration)?
and, a lesser point, what makes us think that we can so perfectly balance to
the ZERO flux point, anyway?
i'm sure there is some old text on the subject, and it might be a fun
experiment to observe. but i don't have the time or inclination for this
research. some things are easier to simply accept at face value.
but it's always fun to put some science behind a phenomenon,
rather than accept some mystic hype... ;)
gotta get back to work,
bob.d.
> ----------
> From: Allen Wright[SMTP:AllenVSE@compuserve.com]
> Sent: Wednesday, October 18, 2000 5:56 AM
> To: aJoeNet
> Subject: [JN] Parafeed?
>
> Joes and Joette(s),
> Re Parafeed:
>
> I am not trying to be smart here - Parafeed is strongly recommended by
> some
> serious heavy hitters, yet I have these conflicts:
>
> a/ It is my understanding that one of the generally assumed "problems"
> with
> push-pull topology is that without signal the OPT sits with zero flux
> (assuming the DC standing currents are balanced) and that when some signal
> arrives the OPT must swing through a quite non-linear segment of it's BH
> curve before reaching a more optimum portion. And does this non-linear to
> linear dance on every zero crossing transition of the signal. Yes?
>
> b/ A (conventional) SE amp correctly matched to it's (air-gapped) OPT runs
> a standing current that places it's operating condition right in the
> middle
> of the most linear part of the BH curve area - and in normal operation
> should never swing down (or up) as far as the curved portion the P-P amp
> cannot advoid. Yes?
>
> c/ And this standing current in the OPT is one of the theroretical
> advantages of the SE topology - Yes?
>
> d/ A single ended parafeed amp (normally) is is choke loaded and cap feeds
> an OPT - which doesn't have/need an air gap because it doesn't carry any
> DC
> current. Yes?
>
> Question 1: Why then doesn't a parafeed amp suffer exactly the same "non
> linearity" around the zero crossing point that P-P (supposedly) does?
>
> Question 2: If it does have this non linear distortion due to the BH
> curve,
> what are the theoretical advantages of parafeed that outweigh this and yet
> are not possible in a PP design?
>
> Very curious on these points...
>
> Allen (VSE)
>
>
>
>
>
=========================================================================
From: Thomas Danley <Tom@ppci.com>
Subject: Re: [JN] Parafeed?
Date: Wed, 18 Oct 2000 11:34:57 -0500
Source: Sound Digest Archive v02.n697
"T. Loesch" wrote:
> snip>
>
> It is (IMHO) a problem, but many specifically for parafeed and similar
> operation designed transformers incorporate a certain percentage of "better"
> core material, be it Permalloy, Nickel or MuMetal, all of which reduce the
> distortion.
>
> Later T
> _________________________________________________________________________
Hi
If one looked at the BH curves alone, one would conclude that the material which
had the least magnetic non linearity would be the best (distortion wise) and one
would not want to use square loop materials which has significant magnetic
Hysteresis.
As the non linearity that effects the audio signal is caused by the non linear
magnetizing current, not magnetic non linearity, one can substitute a more non
linear material IF it also has sufficiently high permeability to raise the
impedance of the magnetizing current to offset the more non linear material.
Switching a to a Square Permaloy core, one find that the material is "less
linear" but the permeability is 6-8 times that of sil steel and as the Bmax is
about half, twice the turns per volt are needed. The result is a much higher
inductance and much less magnetizing current..
Although the magnetizing impedance now has more non linearity, its current is
much smaller with respect to the audio signal and so has much less effect on it.
Going the other direction, one might use the same analysis on the effect of an
air gap on linearity (not considering the DC portion). It looks like to me is
that an air gap actually has no effect on the non linear portion of the
magnetizing current
Adding an air gap does lower the magnetic circuit permeability and this lowers
the magnetizing impedance in parallel with the source/load.
Measuring the magnetic circuits non linearity would show a more linear circuit,
how ever since it is the nonlinear impedance related to the source / load that
really matters it is not that simple. The nonlinear current (needed to swing
the core's iron around its Hysteresis loop) is actually unchanged (you have not
changed the core material just added a totally linear air gap in series.
The effect is I think like connecting a totally pure resistance in parallel with
a larger but non linear resistance, the pure resistance does hide the non
linearity but it does not change the magnitude of the non linear part.
Cheers,
Tom Danley
=========================================================================
From: dslagle@earthlink.net (dave slagle)
Subject: Re: [JN] Parafeed?
Date: Wed, 18 Oct 2000 11:59:29 -0400
Source: Sound Digest Archive v02.n697
Dare i get involved with some opinions... oh why not.
>a/ It is my understanding that one of the generally assumed "problems" with
>push-pull topology is that without signal the OPT sits with zero flux
>(assuming the DC standing currents are balanced) and that when some signal
>arrives the OPT must swing through a quite non-linear segment of it's BH
>curve before reaching a more optimum portion. And does this non-linear to
>linear dance on every zero crossing transition of the signal. Yes?
it has been presented to me, and i agree with the idea that the zero
crossing is not an issue at all, the real bugaboo comes with the use of non
gapped transformers...
again.. look at...
<http://albums.photopoint.com/j/View?u=37049&a=237580&p=30886175&Sequence=0&
res=high>
note thatr the gapped core has no opening in the loop, which to me means
the up and down if you will follow the same line. the interleaved core has
a noted opening, which means the up and down follow different paths.. its
the opening of the loop that gives us the alleged distortion, not the zero
crossing... in other words, put a small amount of DC through the
interleaved core to bias it 1/2 way to saturation, you will still get a
minor loop with an opening... so to me the zero crossing is a bit
misleading, the problem comes with that damn open B-H loop.
looking at my curves, the most linear part seems to be at the zero crossing...
>c/ And this standing current in the OPT is one of the theroretical
>advantages of the SE topology - Yes?
i see it as the DC forces you to gap it which gives you a more linear
core... it closes the loop... this is why partridge and crowhurst advocated
gapped PP trannies.
from ironman
>A closing comment:
>
>The same disadvantage of the PP output transformer is present with
>input transformers. Even more so, as these operate at far lower
>signal levels. I never heard a detoriation in sound when I added an
>input trabsformer to a conventinal SE amp.
right... but they use materials like nickel that have a much narrower loop
to begin with... if all this zero crossing were the problem the whole
recording industry would be doomed!.. but somehow they got by...
dave
=========================================================================
From: tube@jump.net
Subject: Re: [JN] Parafeed?
Date: Wed, 18 Oct 2000 12:07:59 -0500
Source: Sound Digest Archive v02.n697
Allen Wright wrote:
> b/ A (conventional) SE amp correctly matched to it's (air-gapped) OPT runs
> a standing current that places it's operating condition right in the middle
> of the most linear part of the BH curve area - and in normal operation
> should never swing down (or up) as far as the curved portion the P-P amp
> cannot advoid. Yes?
I wondered about this for many years, until the following sequence of
thoughts finally hit me. The "zero-crossing" point of the B-H curve is
largely a myth. It exists only when the first note rises; as soon as
the signal reverses direction it dissappears, never to be seen again.
Instead, the signal travels through this non-linear region every single
time the signal reverses direction, no exceptions. A transformer with a
DC flux therefore has an advantage on the first quarter of the first
note, after which, like all other transformers, it must pass through
the non-linear region on every reversal. An "extra" distortion point at
the zero flux point does not exist if the transformer is "coming down"
from a point of higher flux, which you can easily verify by looking at
the usual hysteresis loops.
I think that the effect of all this is to vary the overall inductance
of the transformer at each reversal, with a low initial inductance
changing to a high inductance once it gets past the knee, the non-
linear region. For very high frequency signals this should have little
if any effect, but for low frequency signal it means that the signal
shifts in phase, by quite a lot, at the beginning of each reversal. The
good news here is that the low frequncy signals are also the big
signals, so this effect only occurs at the beginning of each signal.
Now, having said that, is there anything we can do to minimize this? I
am still confused on this subject, but an obvious is to use a material
that has low non-linearity. This will occur if the initial and maximum
permeabilities of the core are fairly close in value, which means that
the inductance will not change much; the material has very little non-
linearity to begin with. The two best "common" materials that I am
aware of are Sendust and 1040 Alloy, with initial and maximum
permeabilities of 30K/120K and 40K/100K respectively, giving them a
4:1 ratio (Sendust) and a 2.5:1 ratio (1040 Alloy) of max. to min.
permeabilities. This may sound like a lot but compare them to materials
like grain-oriented Silicon-Iron, 1.5K/40K, a ratio of 27:1, or 68
Permalloy, 250K/1.2K, a ratio of 208:1! Now that's non-linearity! There
are other materials that have ratios much better than 1040 Alloy, by
the way. I can't find much information on Mike's Cobalt alloy materials
but what I have seen suggests that a ratio of 7:1 or lower is very
possible. Because of the very high expense of Cobalt, I HOPE they sound
terrible, so I can forget about them, but they probably sound fantastic
(I am convinced that God hates Wealth, and finds ever more creative
ways to cause us to part with what little we have ...).
Another big factor, however, is the air-gap. The equations get too
complicated for me, involving core area, length, etc., but a fairly
good simplification is to view them like capacitors, which when added
in series have an overall reduction. If the air-gap has a
"permeability" of 100, then this air-gap plus a steel core of 1.5K/40K
gives an overall of 100 + 1.5K = 93.75 overall, up to 100 + 40K =
99.75, a ratio of min to max permeabilities of just 1.064:1, or about
6.4%. This is obviously so low that we don't have to worry about it,
although the real numbers using the real equations are not quite this
good. Still, we can easily see why an air-gap "linearizes" the magnetic
flux. What confuses me is that Partridge derived all this, but then
went on to say that for some reason, an air-gap results in NO decrease
in distortion. ??? He then went on to say we should include one anyway.
??? I don't have a clue about either of these statements, and I have
about decided to pretend that he never said them, so I can forget about
them.
Other factors exist, however. It may be that, all other things being
equal, the Nickel/Cobalt/other exotic cores sound better due to very
high initial permeabilities, making them more sensitive to the very
small signals, allowing more music to get through. As long as the
initial permeability is quite high--78 Permalloy has 8K/100K, with a
ratio of 12.5:1--a very small air-gap (high permeability) will provide
very low distortion. Here an air-gap of 600, allowing 6 times the
primary inductance of the 100 air-gap of steel, has a ratio of 1.067:1
or about 6.7%.
Overall then, it does sound to me like we still need an air-gap with
parafeed, unless the really, really exotic materials are used, but it
can be a very small air-gap indeed. Parafeed allows us to forget about
the DC limitations of exotic materials. Actually, as long as it has a
very small air-gap, it allows us to forget about EVERYTHING except the
basic nature of the core materials, allowing us to choose them on the
pure basis of "what sounds best", instead of being limited to materials
which can handle high DC current levels, or having to accept a massive
increase in core size, which costs much more and reduces the frequency
range of any transformer.
Phil
=========================================================================
From: "T. Loesch" <ezee_e@hotmail.com>
Subject: Re: [JN] Parafeed?
Date: Wed, 18 Oct 2000 14:53:00 GMT
Source: Sound Digest Archive v02.n697
Hi,
>This sounded good, but had the LF EQ effects, Thorsten
>described. In fact the LF response started to rise below
>40Hz to as much as +6dB at 20Hz. This gave the impression of
>a very good bass response, not unpleasant or phony at all.
>Since my speakers don't go too low this compensated somewhat.
Yes, my take very much as well. Of course, simply increasing the Capacitor
reduces the Pole proportionally out of harms way if that is desired.
>But it had instability problems. Whenever the line voltage
>surged or sagged a litte, there would be an immense low freq
>pulse.
Yes, I do have a reason of using some form of regulation....
>My conclusions out of this (may be valid, may be not):
The Parafeed output Transformers you use, what is the core
material?Grainoriented steel or something freakier?
>Distortion introduced by the BH-nonlinearity of ungapped transformers
>is not very noticable to the human ear ? And this might not really
>be a problem of PP ?
It is (IMHO) a problem, but many specifically for parafeed and similar
operation designed transformers incorporate a certain percentage of "better"
core material, be it Permalloy, Nickel or MuMetal, all of which reduce the
distortion.
Later T
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=========================================================================
From: thomas.mayer@philips.com
Subject: Re: [JN] Parafeed?
Date: Wed, 18 Oct 2000 16:31:26 +0200
Source: Sound Digest Archive v02.n697
Allen, all,
Although I haven't experimented too much with parafeed yet,
and didn't build a PP amp (yet) I have some experience and
thoughts which might be worth sharing.
I have not used parafeed in a power amp, but the two stages
in my phono preamp are parafed. Before switching to parafeed
I had a variant of the so called ultrapath topology in the
phonostage. Ultrapath connects the last B+ bypass cap to the
cathode of the tube instead of ground. While the 'common'
ultrapath has another cap from B+ to ground, I omitted that.
The last cap going to the cathode is directly connected
to the last choke of the PS filter.
This sounded good, but had the LF EQ effects, Thorsten
described. In fact the LF response started to rise below
40Hz to as much as +6dB at 20Hz. This gave the impression of
a very good bass response, not unpleasant or phony at all.
Since my speakers don't go too low this compensated somewhat.
But it had instability problems. Whenever the line voltage
surged or sagged a litte, there would be an immense low freq
pulse.
I guess the primary inductance of the interstage transformer
in series with the coupling cap to the cathode was essentially
a short at the resonant frequency, creating positive feedback
from plate to cathode. Due to the low resonant frequency
(below 10 Hz) this didn't create a sustained LF oscillation.
To get rid of that, I switched to parafeed. coupling cap in
the ground leg, also connected to the cathode, not ground
"ultra-para-feed" "short-parafeed" ? Name it what you want.
Although this still has the problem of the short at the
resonant frequency, the resonance is far lower due to the
much higher primary inductance of the parafeed transformer.
In fact it is out of the frequency band of the phonostage now.
No LF EQ effect any more. Also stable when the line saggs or
surges. the same number of components in the signal path as
before: tube, transformer, cap. The same choke as plate load,
as I used with the gapped transformer (it's a suitable plate
choke). Same cap.
To my surprise those two configurations had very similar
sound characteristics. In fact the only relevant difference
was the lack of stability and EQ effect of the parafeed
solution. many of you have heard this topology in Arhus.
Bear in mind that this is a phonostage, so it's far upstream
the signal path. Sound differences whould be very apparent
My conclusions out of this (may be valid, may be not):
> a/ It is my understanding that one of the generally assumed "problems" with
> push-pull topology is that without signal the OPT sits with zero flux
> (assuming the DC standing currents are balanced) and that when some signal
> arrives the OPT must swing through a quite non-linear segment of it's BH
> curve before reaching a more optimum portion. And does this non-linear to
> linear dance on every zero crossing transition of the signal. Yes?
Distortion introduced by the BH-nonlinearity of ungapped transformers
is not very noticable to the human ear ? And this might not really
be a problem of PP ?
> b/ A (conventional) SE amp correctly matched to it's (air-gapped) OPT runs
> a standing current that places it's operating condition right in the middle
> of the most linear part of the BH curve area - and in normal operation
> should never swing down (or up) as far as the curved portion the P-P amp
> cannot advoid. Yes?
> c/ And this standing current in the OPT is one of the theroretical
> advantages of the SE topology - Yes?
Maybe more of a theoretical (measurable) advantage than an audible ?
> d/ A single ended parafeed amp (normally) is is choke loaded and cap feeds
> an OPT - which doesn't have/need an air gap because it doesn't carry any DC
> current. Yes?
>
> Question 1: Why then doesn't a parafeed amp suffer exactly the same "non
> linearity" around the zero crossing point that P-P (supposedly) does?
The parafeed amp still has the advantage of fewer compionents in
the signal path. Just one tube instead of two, A continues primary
instead a split (and possibly mismatched) one.
> Question 2: If it does have this non linear distortion due to the BH curve,
> what are the theoretical advantages of parafeed that outweigh this and yet
> are not possible in a PP design?
No matching problems ?
A closing comment:
The same disadvantage of the PP output transformer is present with
input transformers. Even more so, as these operate at far lower
signal levels. I never heard a detoriation in sound when I added an
input trabsformer to a conventinal SE amp.
Ciao ... Thomas
=========================================================================
From: David Barnett <d_n_b@swbell.net>
Subject: Re: [JN] Parafeed?
Date: Wed, 18 Oct 2000 13:07:00 -0500
Source: Sound Digest Archive v02.n698
On Wed, 18 Oct 2000 10:22:25 +0000 (GMT), "T. Loesch"
<ezee_e@hotmail.com> wrote:
>I commented before that IMHO much of the "improved bass" with parafeed is in
>fact a resonance phenomenae between the way to small coupling Cap and the
>involved inductances, leading to an EQ, to the tune of as much as 3 - 4db at
>LF....
I've always wondered about the wisdom of replacing one reactance with
three...
- --dnb
=========================================================================
From: Paul Joppa <pdjoppa@home.com>
Subject: Re: [JN] Parafeed?
Date: Thu, 19 Oct 2000 01:17:59 -0700
Source: Sound Digest Archive v02.n699
Hi all-
Sorry I came into this late. Fortunately I read the next two digests, so
a lot of what I wanted to say has already been said. To the best of my
knowledge, Bob Danielak and Tom Danley have described the situation
pretty well. I'll throw in my support of their comments below, in answer
to Allen Wright's questions.
> a/ It is my understanding that one of the generally assumed "problems" with
> push-pull topology is that without signal the OPT sits with zero flux
> (assuming the DC standing currents are balanced) and that when some signal
> arrives the OPT must swing through a quite non-linear segment of it's BH
> curve before reaching a more optimum portion. And does this non-linear to
> linear dance on every zero crossing transition of the signal. Yes?
This is a bogus "problem". Push-pull does not suffer from any such
magnetic difficulty; it is a confusion based on the common practice of
magnetic textbooks, which describe what happens when you start from a
completely demagnetized material in order to explain the hysteresis
loop. As soon as the music starts, the transformer no longer sits at
zero flux even during the quiet passages; it has a history. Unless it is
carefully demagnetized, it will never again start from zero. You can
hear this with parafeed amps (those that do not incorporate protection
from startup transients) - they are magnetized by the startup transient,
and often must play music for an hour or so before they sound "right" -
that is, the music acts as a partial demagnetizing signal.
> b/ A (conventional) SE amp correctly matched to it's (air-gapped) OPT runs
> a standing current that places it's operating condition right in the middle
> of the most linear part of the BH curve area - and in normal operation
> should never swing down (or up) as far as the curved portion the P-P amp
> cannot advoid. Yes?
No, that's another misunderstanding. For small signals, the local
nonlinearity and hysteresis look the same no matter what the DC bias (as
long as it is well away from saturation). For large signals, a DC biased
transformer will saturate on positive peaks but not on negative ones, so
a too-small transformer will have overload (saturation) distortion that
has more even harmonics and less odd harmonics if it is DC biased. But
if the transformer is designed so that it never enters saturation in
normal operation, the distortion is the same whether there is DC bias or
not.
> c/ And this standing current in the OPT is one of the theroretical
> advantages of the SE topology - Yes?
No, it's another myth. There is a grain of truth in it, though. If a
transformer is airgapped to handle the DC, it may be larger and have
more turns in order to restore some of the inductance lost to the air
gap. Since the distortion depends on the core (not the air gap), this
larger core with more turns will have less distortion. But that's
because the core is bigger, not because it is air gapped or has DC in
it. A push-pull transformer on the same large core with the same number
of turns will have the same reduced distortion.
> d/ A single ended parafeed amp (normally) is is choke loaded and cap feeds
> an OPT - which doesn't have/need an air gap because it doesn't carry any DC
> current. Yes?
Yes.
> Question 1: Why then doesn't a parafeed amp suffer exactly the same "non
> linearity" around the zero crossing point that P-P (supposedly) does?
As above, there is no such excess nonlinearity mechanism, and neither
parafeed not push-pull amps suffer from it.
> Question 2: If it does have this non linear distortion due to the BH curve,
> what are the theoretical advantages of parafeed that outweigh this and yet
> are not possible in a PP design?
The theoretical advantages of parafeed are basically the same as
push-pull, the linear range (without saturation) of the output
transformer is larger so the transformer can be smaller. It's an
incidental advantage that with a smaller transformer the leakage
inductance is smaller, so less interleaving is necessary to obtain a
satisfactory bandwidth, and therefor the leakage capacitance can be kept
small. The real (still theoretical) advantage is the smaller
transformer. In the old days, this was very important for AM
transmitters, which used a DC-carrying transformer to modulate the RF
output stage. The total amount of iron required to meet a given power
and bandwidth requirement is much less for parafeed than for a single
airgapped transformer. Reuben Lee has a clear discussion of this,
including photographs of transmitters built to the same specs using both
philosophies - the size difference is staggering. This appears in the
second edition of "Electronic Transformers and Circuits", but does not
appear in the third edition - apparently by 1988 this information had
become irrelevant.
Now for high fidelity use, push-pull has the same advantage as parafeed
(ignoring for the moment the power supply isolation issue). In both
cases the output transformers are smaller for the same power and iron
distortion requirement. The other differences are not due to the
transformer. And note that push-pull has a similar power supply
isolation advantage as parafeed; both are superior in that sense to
"normal" airgapped SE amp designs. My ears still prefer SE sound over
push-pull, but it is not for either magnetic hysteresis or power supply
isolation reasons.
Well, that's my input. This is not the first time I have posted about
this issue, though it's probably the most extensive one. I hope it is
useful.
- -Paul Joppa
=========================================================================
From: thomas.mayer@philips.com
Subject: Re: [JN] Parafeed?
Date: Thu, 19 Oct 2000 09:33:21 +0200
Source: Sound Digest Archive v02.n699
> The Parafeed output Transformers you use, what is the core
> material?Grainoriented steel or something freakier?
It's the Jensen JT-10K61-1M 4:1 line output. According to Jensen
it's a 80% Nickel core.
Thomas
=========================================================================
From: "T. Loesch" <ezee_e@hotmail.com>
Subject: Re: [JN] Parafeed?
Date: Thu, 19 Oct 2000 11:14:28 GMT
Source: Sound Digest Archive v02.n699
Hi Thomas,
>It's the Jensen JT-10K61-1M 4:1 line output. According to Jensen
>it's a 80% Nickel core.
See, try getting such a Transformer on a normal Iron core, not gapped and
listen in horror how bad this CAN be....
Comparative tests can only really attract any claim to general applicability
of the results if "All Else is EQUAL!".... Changing the core material
changes the conditions of the experiment.
Later T
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=========================================================================
From: Dan Marshall <mdaniel7@uswest.net>
Subject: Re: [JN] Parafeed?
Date: Thu, 19 Oct 2000 06:12:16 +0000
Source: Sound Digest Archive v02.n700
Paul Joppa wrote:
>
> Hi all-
<big snip>
> My ears still prefer SE sound over push-pull, but it is not
> for either magnetic hysteresis or power supply isolation reasons.
Why is it then? I am not disagreeing with you, for I also prefer the
sound of SE over PP, but am not fully convinced that I have heard valid
reasons why SE sounds better, nor do I claim to fully understand why.
A while back I was pontificating about a modified PP circuit I dubbed
Quasi-SE which consisted of driving only one output tube grid of a
cathode-biased PP amp with the cathode bypass cap removed. In this case
the "other" output tube receives its drive (phase inverted) from the
cathode of the first (driven) output tube. Examining the distortion
spectrum reveals that such a configuration does indeed produce a
distortion spectrum quite similar to a SE amp.
I recently conducted a listening test to see whether Quasi SE sounds
like a SE amp. The short answer is that it doesn't. The test was
conducted with a Heath AA-71 amp, which is the later, black-chassis
version of the W4-M amplifier, a PP Williamson design using PP 5881s and
a pair of 6SN7s, both Sylvania chrome domes (which reportedly rate high
in the comparative 6SN7 listening tests). I had checked it out
thoroughly to assure it was in proper operating condition, replete with
having examined the distortion spectrum of both PP and Quasi SE
connection.
With the output stage cathode bypass capacitor and one end of one of the
output stage coupling caps disconnected, I listened to it with that
coupling cap making connection and without (i.e., in Quasi SE and PP).
Though the harmonic distortion spectrum was decidedly different in Quasi
SE, I could not discern any difference whatsoever in the way it
sounded. Neither connection sounded as good as a true SE amp. So, that
sort of shoots down the argument that that SE amps sound better because
they produce a distortion spectrum which the ear prefers, nor do I buy
the argument that it is because of poor phase inversion. Phase
inversion can be accomplished with a high degree of precision at audio
frequencies. I still do not fully comprehend why SE sounds better than
PP. And then, there are those who argue that SE doesn't sound better.
Some have said that Allen Wright's PP design is quite good, though I
have never heard it. So I guess I am still in the dark. Perhaps the
Quasi SE/PP listening comparison should be conducted with a triode, no
feedback amp.
Dan Marshall
<snip>
>
> -Paul Joppa
=========================================================================
From: Allen Wright <AllenVSE@compuserve.com>
Subject: Re: [JN] Parafeed?
Date: Thu, 19 Oct 2000 08:05:37 -0400
Source: Sound Digest Archive v02.n700
Various people wrote good and clear answers to my puzzles on SE, PP and
Parafeed.
Thank you all!
Allen (VSE)
=========================================================================
From: "BobC" <bobcx@bellatlantic.net>
Subject: Re: [JN] Parafeed?
Date: Thu, 19 Oct 2000 08:53:23 -0400
Source: Sound Digest Archive v02.n700
- ----- Original Message -----
From: "Allen Wright" <AllenVSE@compuserve.com>
To: "aJoeNet" <sound@lists.io.com>
Sent: Thursday, October 19, 2000 8:05 AM
Subject: Re: [JN] Parafeed?
> Various people wrote good and clear answers to my puzzles on SE, PP and
> Parafeed.
>
> Thank you all!
>
> Allen (VSE)
Allen,
There is some more worthwhile information on this very subject on the SET
forum. Here is a link. http://www.audioasylum.com/forums/SET/bbs.html
This is the thread: ( I don't know nothin' 'bout transformers, but...)
take care
Bob
=========================================================================
From: TubeGarden@aol.com
Subject: Re: [JN] Parafeed?
Date: Thu, 19 Oct 2000 09:06:47 EDT
Source: Sound Digest Archive v02.n700
In a message dated 10/19/00 1:24:38 AM US Mountain Standard Time,
pdjoppa@home.com writes:
> Now for high fidelity use, push-pull has the same advantage as parafeed
> (ignoring for the moment the power supply isolation issue). In both
> cases the output transformers are smaller for the same power and iron
> distortion requirement. The other differences are not due to the
> transformer.
Greets!
Thank you for the information :)
I will try parafeed again when Steve Bench figures out how to do it without a
cap :)
Happy Ears!
Al B^}
=========================================================================
From: "BobC" <bobcx@bellatlantic.net>
Subject: Re: [JN] Parafeed?
Date: Thu, 19 Oct 2000 10:39:45 -0400
Source: Sound Digest Archive v02.n700
- ----- Original Message -----
From: "Paul Joppa" <pdjoppa@home.com>
To: <sound@lists.io.com>
Sent: Thursday, October 19, 2000 4:17 AM
Subject: Re: [JN] Parafeed?
> Hi all-
> SNIP<
Thanks for the excellent post Paul.
Bob
=========================================================================
From: "T. Loesch" <ezee_e@hotmail.com>
Subject: RE: [JN] Parafeed?
Date: Thu, 19 Oct 2000 13:37:50 GMT
Source: Sound Digest Archive v02.n700
Hi there,
>I agree that the difference in sound after the first 3/4 hour is something
>to hear. The amp goes from distant, vieled and compressed, then comes alive
>like some sleeping giant.
Funny. My system is of the "just switch it on and play music".... Once
operating points have stabilised (around 5min) it plays music as cleanly,
sweetly and so on as it will after 10 Hours....
Later T
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=========================================================================
From: David Home <David_Home@creoscitex.com>
Subject: RE: [JN] Parafeed?
Date: Thu, 19 Oct 2000 14:44:01 +0200
Source: Sound Digest Archive v02.n700
Paul Joppa wrote:
>You can
>hear this with parafeed amps (those that do not incorporate protection
>from startup transients) - they are magnetized by the startup transient,
>and often must play music for an hour or so before they sound "right" -
>that is, the music acts as a partial demagnetizing signal.
Hi Paul.
I remember John Cammile(sp?) putting a shorting relay across the primary of the nickel output to pre
vent this problem at start up. I thought at the time though, in the big picture of amp warm up, if t
he need is really there. I have BG caps in my pre-amp, tubes in the phono amp & pre-amp, etc that al
so need time to open up. I decided that dealing with this problem of magnetization would not really
improve my musical enjoyment enough to justify the needed parts and work. I agree that the differenc
e in sound after the first 3/4 hour is something to hear. The amp goes from distant, vieled and comp
ressed, then comes alive like some sleeping giant.
Now I certainly could be rationalizing to justify my laziness, and would like your comments. If I ca
n get to good listening within 15 minutes rather then 40, then the work is worthwhile. In your opini
on, is the magnetization the principle bottleneck?
Regards, David
- -----Original Message-----
From: Paul Joppa [mailto:pdjoppa@home.com]
Sent: Thursday, October 19, 2000 10:18 AM
To: sound@lists.io.com
Subject: Re: [JN] Parafeed?
Hi all-
Sorry I came into this late. Fortunately I read the next two digests, so
a lot of what I wanted to say has already been said. To the best of my
knowledge, Bob Danielak and Tom Danley have described the situation
pretty well. I'll throw in my support of their comments below, in answer
to Allen Wright's questions.
> a/ It is my understanding that one of the generally assumed "problems" with
> push-pull topology is that without signal the OPT sits with zero flux
> (assuming the DC standing currents are balanced) and that when some signal
> arrives the OPT must swing through a quite non-linear segment of it's BH
> curve before reaching a more optimum portion. And does this non-linear to
> linear dance on every zero crossing transition of the signal. Yes?
This is a bogus "problem". Push-pull does not suffer from any such
magnetic difficulty; it is a confusion based on the common practice of
magnetic textbooks, which describe what happens when you start from a
completely demagnetized material in order to explain the hysteresis
loop. As soon as the music starts, the transformer no longer sits at
zero flux even during the quiet passages; it has a history. Unless it is
carefully demagnetized, it will never again start from zero. You can
hear this with parafeed amps (those that do not incorporate protection
from startup transients) - they are magnetized by the startup transient,
and often must play music for an hour or so before they sound "right" -
that is, the music acts as a partial demagnetizing signal.
> b/ A (conventional) SE amp correctly matched to it's (air-gapped) OPT runs
> a standing current that places it's operating condition right in the middle
> of the most linear part of the BH curve area - and in normal operation
> should never swing down (or up) as far as the curved portion the P-P amp
> cannot advoid. Yes?
No, that's another misunderstanding. For small signals, the local
nonlinearity and hysteresis look the same no matter what the DC bias (as
long as it is well away from saturation). For large signals, a DC biased
transformer will saturate on positive peaks but not on negative ones, so
a too-small transformer will have overload (saturation) distortion that
has more even harmonics and less odd harmonics if it is DC biased. But
if the transformer is designed so that it never enters saturation in
normal operation, the distortion is the same whether there is DC bias or
not.
> c/ And this standing current in the OPT is one of the theroretical
> advantages of the SE topology - Yes?
No, it's another myth. There is a grain of truth in it, though. If a
transformer is airgapped to handle the DC, it may be larger and have
more turns in order to restore some of the inductance lost to the air
gap. Since the distortion depends on the core (not the air gap), this
larger core with more turns will have less distortion. But that's
because the core is bigger, not because it is air gapped or has DC in
it. A push-pull transformer on the same large core with the same number
of turns will have the same reduced distortion.
> d/ A single ended parafeed amp (normally) is is choke loaded and cap feeds
> an OPT - which doesn't have/need an air gap because it doesn't carry any DC
> current. Yes?
Yes.
> Question 1: Why then doesn't a parafeed amp suffer exactly the same "non
> linearity" around the zero crossing point that P-P (supposedly) does?
As above, there is no such excess nonlinearity mechanism, and neither
parafeed not push-pull amps suffer from it.
> Question 2: If it does have this non linear distortion due to the BH curve,
> what are the theoretical advantages of parafeed that outweigh this and yet
> are not possible in a PP design?
The theoretical advantages of parafeed are basically the same as
push-pull, the linear range (without saturation) of the output
transformer is larger so the transformer can be smaller. It's an
incidental advantage that with a smaller transformer the leakage
inductance is smaller, so less interleaving is necessary to obtain a
satisfactory bandwidth, and therefor the leakage capacitance can be kept
small. The real (still theoretical) advantage is the smaller
transformer. In the old days, this was very important for AM
transmitters, which used a DC-carrying transformer to modulate the RF
output stage. The total amount of iron required to meet a given power
and bandwidth requirement is much less for parafeed than for a single
airgapped transformer. Reuben Lee has a clear discussion of this,
including photographs of transmitters built to the same specs using both
philosophies - the size difference is staggering. This appears in the
second edition of "Electronic Transformers and Circuits", but does not
appear in the third edition - apparently by 1988 this information had
become irrelevant.
Now for high fidelity use, push-pull has the same advantage as parafeed
(ignoring for the moment the power supply isolation issue). In both
cases the output transformers are smaller for the same power and iron
distortion requirement. The other differences are not due to the
transformer. And note that push-pull has a similar power supply
isolation advantage as parafeed; both are superior in that sense to
"normal" airgapped SE amp designs. My ears still prefer SE sound over
push-pull, but it is not for either magnetic hysteresis or power supply
isolation reasons.
Well, that's my input. This is not the first time I have posted about
this issue, though it's probably the most extensive one. I hope it is
useful.
- -Paul Joppa
=========================================================================
From: Christian Rintelen <christian@rintelen.ch>
Subject: [JN] parafeed and cap sizes
Date: Mon, 23 Oct 2000 13:05:56 +0200
Source: Sound Digest Archive v02.n705
Thorsten Loesch wrote about his para-fedup experience:
> Coupling Capacitor was 22uF Ansar Supersound.
>
The large cap values needed for fullrange parafeed have always bothered me. Of
course it is possible to build a good sounding 22 uF cap. But it's easier to
build a good 2.2 uF cap. And it's even easier to build a good 0.22 uF cap. I
hope you get the drift...
You'd want a cap to store and release energy as fast as possible. I don't know
if it's correct to do so, but I'd like to compare caps with muscles. Imagine a
big and a small muscle that can "store" (or release) the same amount of energy.
I'd bet that the smaller muscle with the higher "energy per fibre" coefficient
will release the energie faster and more "explosive" than the bigger muscle.
Now take a 100 uF polyprop cap and a 100 uF tantalum cap, both of course with
the same voltage rating. The poly will inevitably be huge, whilst the tantalum
can be built very small. Has anybody ever measured how fast the two caps can
release the same amount of energy (joules, volts - whatever you want)? (I
haven't - it's not a rhetorical question!)
Please note: I'm NOT talking about how a polyprop and a tantalum cap sound in
that specific use, just how fast they can store and/or release energy.
Christian
PS. If you want to witness the density of the stored energy, just reverse the
polarity on a tantalum cap... DON'T DO THIS AT HOME, KIDS - the mess is
tremendous and the bang fare more impressive than with a conventional
electrolytic cap of the same capacity! (I was very lucky to wear glasses when
it happened to me. 'nuff said.)
=========================================================================
From: "T. Loesch" <ezee_e@hotmail.com>
Subject: Re: [JN] parafeed and cap sizes
Date: Mon, 23 Oct 2000 14:24:03 GMT
Source: Sound Digest Archive v02.n705
Hi all,
>The large cap values needed for fullrange parafeed have always bothered me.
Well, in classic SE the final PSU Filter Cap and the Cathode Bypass Cap (if
used) are needed to complete the AC current loop. So what you are happy to
use as PSU Cap will be equally fine as Parafeed Cap... ;-)
Later T
PS, blowing up Cap's is way more fun with the Huge (say 47,000uF 40V) Can
Capacitors and a Variac. Almost like a handgranade. Best keep it outside the
house. We one blew a hole into a roof blowing one of these up.
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From: "T. Loesch" <ezee_e@hotmail.com>
Subject: Re: [JN] parafeed and cap sizes
Date: Mon, 23 Oct 2000 15:10:22 GMT
Source: Sound Digest Archive v02.n705
Hi all,
>In both versions it is possible to use the ultrapath "trick"
>which feeds the signal path to the cathode directly and thus
>bypassing cathode resistor/cap combination.
Even better. If, in the classic SE Circuit the additional "Ultrapth"
Capacitor is sized suitably (Ck / 1+Mu) we achive around 20db better PSRR
and have a current loop that is equally short.
>Since the parafeed circuit is better isolated from the PS through
>the plate load choke, can we assume that the cap in the B+ has
>less influence on the sound ? Opinions ?
Yup, agreed. A correctly tuned "Ultrapath with Cathode bypass cap" classic
SE Circuit allows the same though.
>I came to the conclusion, that parafeed has just as many parts in the
>signal path.
Almost yes, the Anode load choke comes into the signal path and is extra.
Later T
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From: thomas.mayer@philips.com
Subject: Re: [JN] parafeed and cap sizes
Date: Mon, 23 Oct 2000 15:12:02 +0200
Source: Sound Digest Archive v02.n705
Christian,
> The large cap values needed for fullrange parafeed have always bothered me.
In a "regular" circuit with DC in the transformer, you
have a cap in the signal path which is just as large.
That's the last cap in your power supply.
While the signal loop goes through tube, coupling cap, transformer,
cathode resistor + bypass cap with parafeed, with conventional
circuits it sees: tube, transformer, B+ cap, cathode resistor +
bypass cap. Very similar.
In both versions it is possible to use the ultrapath "trick"
which feeds the signal path to the cathode directly and thus
bypassing cathode resistor/cap combination.
Since the parafeed circuit is better isolated from the PS through
the plate load choke, can we assume that the cap in the B+ has
less influence on the sound ? Opinions ? My experience shows
exactly this. I came to the conclusion, that parafeed has just as
many parts in the signal path.
Ciao ... Thomas
=========================================================================
From: "Sikking, Peter" <peter.sikking@nomura.co.uk>
Subject: RE: [JN] parafeed and cap sizes
Date: Mon, 23 Oct 2000 15:17:15 +0100
Source: Sound Digest Archive v02.n705
Christian wrote:
- --Thorsten wrote:
> Coupling Capacitor was 22uF Ansar Supersound.
- --The large cap values needed for fullrange parafeed have
always bothered me.
I maybe wrong, but every time I compare PF stages to series fed stages
I notice that not, like a lot of people moan about, a cap has been added,
but just moved position, from a decoupling (SF) to a coupling (PF) position.
Now I would like to bet that for any given amp-builder:
minimum decoupling (SF) cap >= maximum coupling (PF) cap
And like you say, the smaller the cap, the higher the chance of getting
some quality.
Later,
--Peter
: music lover : ultra-fi builder : ui designer & developer : on drums...
: from:amsterdam@london.uk : +44 20 7521 1070 : facsimile +44 20 7521 3686
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=========================================================================
From: "Sikking, Peter" <peter.sikking@nomura.co.uk>
Subject: RE: [JN] parafeed and cap sizes
Date: Mon, 23 Oct 2000 16:56:42 +0100
Source: Sound Digest Archive v02.n705
T wrote:
- --Even better. If, in the classic SE Circuit the additional "Ultrapth"
Capacitor is sized suitably (Ck / 1+Mu)[...]
It's Ck/mu.
The "+ 1" for kathode amplification falls out of the equation for maximum
PSRR if you solve it.
Still testing this set-up at home. Starting to think that it sounds
a bit to much like AC feedback to me. I may be wrong...
(Thomas:)
> I came to the conclusion, that parafeed has just as many
parts in the signal path.
- --Almost yes, the Anode load choke comes into the signal path
and is extra.
I'd like to think more that one swaps a PS choke & decoupling cap (SF)
for a plate choke and coupling cap (PF) combo.
--Peter
: music lover : ultra-fi builder : ui designer & developer : on drums...
: from:amsterdam@london.uk : +44 20 7521 1070 : facsimile +44 20 7521 3686
PLEASE READ: The information contained in this e-mail is confidential
and intended for the named recipient(s) only. If you are not an intended
recipient of this email you must not copy, distribute or take any
further action in reliance on it and you should delete it and notify the
sender immediately. Email is not a secure method of communication and
Nomura International plc cannot accept responsibility for the accuracy
or completeness of this message or any attachment(s). Please check this
e-mail for virus infection, for which Nomura International plc accepts
no responsibility. If verification of this email is sought then please
request a hard copy. Unless otherwise stated any views or opinions
presented are solely those of the author and do not represent those of
Nomura International plc. This email is intended for informational
purposes only and is not a solicitation or offer to buy or sell
securities or related financial instruments. Nomura International plc is
regulated by the Securities and Futures Authority Limited and is a
member of the London Stock Exchange.
=========================================================================
From: ToobWiz@aol.com
Subject: [JN] Parafeed with a ressitor as plate load
Date: Sun, 30 Sep 2001 10:09:42 EDT
Source: Sound Digest Archive v02.n986
Has anyone tried this? I've so completely associated parafeed with the
existence of a choke (or CCS) as the plate load that I never considered the
simple resistor. Just now, I was looking through the first few pages of my
RDH3 (1941) and the expample of parafeed shown uses a resistor.
now, I'm aware that the choke has better performance in both AC and DC
regimes than a resistor. However, that comes at a high price. It is at times
easy to provide the much greater B+ to equalize the DC performance, but then
what about the AC performance?
What really counts is "How does it sound?" and it is not rare that we find
something which sounds better than theory says "it should" (this is
technically known as the "Al Marcy Effect" :-)
I can visualize a really cheap parafeed SET using an R as a load and a PP OPT
or an autoformer.
????
Cheers/Carron
=========================================================================
From: ToobWiz@aol.com
Subject: Re: [JN] Parafeed with a ressitor as plate load
Date: Sun, 30 Sep 2001 12:47:23 EDT
Source: Sound Digest Archive v02.n986
In a message dated 09/30/2001 12:<BR27:<BR08 PM
Eastern Daylight, hifi@ishoejby.dk writes:
> Yes why not. I have made the same thought, but all were using chokes, so
no...
>
> I dropped the idea, but still have a set of output transformer without
airgap
> that could use a coupling like that.
>
> Any suggestions are welcome.
Jan,
this certainly would work, and would work well technically. My only question
is "How would it sound?"
To do it, one would need to have enough B+ so that the voltage remaining at
the output valve, after subtracting the drop across the load resistor, would
be great enough to allow the chosen operating point.
So, say you wanted to poerate a 2A3 at 270vDC and 60 mA. If your load
resistor is 5K, then you'd drop 300v and therefore require a 570vDC supply.
Now, I don't know that 5K is sufficient load to permit full voltage swing of
the output valve, so maybe you should just try it... or, if you have a much
greater B+ available, use a larger resistor. The OPT is protected against the
high B+ (assuming the parafeed cap is it the top of the OPT), but you would
have to use a standby switch *for sure* to prevent the B+ appearing at the
anode before the filament had warmed.
I'd hope that some of the *real* tube wizards would chime in here to provide
additional cautions and technical details that I might have missed.
It is a really cheap topology, so should be worth a try. I'm surprised that
our good pal Al hasn't already tried it this morning. He seems capable of
(and inclined to) making a new amp every hour :-)
Cheers/Don
=========================================================================
From: SBench@aol.com
Subject: Re: [JN] Parafeed with a ressitor as plate load
Date: Sun, 30 Sep 2001 13:56:36 EDT
Source: Sound Digest Archive v02.n986
In a message dated 01-09-30 12:54:47 EDT, ToobWiz@aol.com writes:
>
> this certainly would work, and would work well technically. My only
question
>
> is "How would it sound?"
>
>
Sounds wonderful. My favorite configuration is 801 / 10k resistor capacitively
coupled to the OPT. 300 volts plate to "cathode", 300 volts drop in the
resistor.
- -Steve
=========================================================================
From: "John Levreault" <jlevro@mediaone.net>
Subject: Re: [JN] Parafeed with a ressitor as plate load
Date: Sun, 30 Sep 2001 15:42:14 -0400
Source: Sound Digest Archive v02.n986
My only concern, and it's only on technical grounds, is that the reflected
output load will now be in parallel with this plate load resistor. So if you
had your 801 cap-coupled to a 10K output tranny, the tube would be seeing
5K. This is where parafeed works out "better" from a technical perspective.
This is less of a concern with a driver stage, since the cap-coupled IT is
usually left unloaded, or very lightly.
In addition, the path back to the power supply is now a resistor instead of
the more-usually-employed choke, so the power supply rejection will be
lower. Many cite this as one of the advantages of parafeed. I just think you
need to be more carefuly with your power supply.
But if it sounds good, then do it!
JL
- ----- Original Message -----
From: <SBench@aol.com>
To: <ToobWiz@aol.com>; <hifi@ishoejby.dk>
Cc: <sound@lists.io.com>
Sent: Sunday, September 30, 2001 1:56 PM
Subject: Re: [JN] Parafeed with a ressitor as plate load
> In a message dated 01-09-30 12:54:47 EDT, ToobWiz@aol.com writes:
>
> >
> > this certainly would work, and would work well technically. My only
> question
> >
> > is "How would it sound?"
> >
> >
>
> Sounds wonderful. My favorite configuration is 801 / 10k resistor
capacitively
> coupled to the OPT. 300 volts plate to "cathode", 300 volts drop in the
> resistor.
>
> -Steve
=========================================================================
From: Jan Nielsen <hifi@ishoejby.dk>
Subject: Re: [JN] Parafeed with a ressitor as plate load
Date: Sun, 30 Sep 2001 18:24:35 +0200
Source: Sound Digest Archive v02.n986
Yes why not. I have made the same thought, but all were using chokes, so no...
I dropped the idea, but still have a set of output transformer without airgap
that could use a coupling like that.
Any suggestions are welcome.
Regards,
Jan
ToobWiz@aol.com wrote:
> Has anyone tried this? I've so completely associated parafeed with the
> existence of a choke (or CCS) as the plate load that I never considered the
> simple resistor. Just now, I was looking through the first few pages of my
> RDH3 (1941) and the expample of parafeed shown uses a resistor.
>
> now, I'm aware that the choke has better performance in both AC and DC
> regimes than a resistor. However, that comes at a high price. It is at times
> easy to provide the much greater B+ to equalize the DC performance, but then
> what about the AC performance?
>
> What really counts is "How does it sound?" and it is not rare that we find
> something which sounds better than theory says "it should" (this is
> technically known as the "Al Marcy Effect" :-)
>
> I can visualize a really cheap parafeed SET using an R as a load and a PP OPT
> or an autoformer.
>
> ????
>
> Cheers/Carron
=========================================================================
From: alan cameron <alan@thehub.com.au>
Subject: Re: [JN] Parafeed with a ressitor as plate load
Date: Mon, 1 Oct 2001 19:26:38 +1000
Source: Sound Digest Archive v02.n986
At 10:09 -0400 30/9/01, ToobWiz@aol.com wrote:
>What really counts is "How does it sound?" and it is not rare that we find
>something which sounds better than theory says "it should" (this is
>technically known as the "Al Marcy Effect" :-)
>
>I can visualize a really cheap parafeed SET using an R as a load and a PP OPT
>or an autoformer.
Don, Joes,
I tried this comparison in a stage to driving a phase splitter tranny
with the high mu section of a 6EA7. on the sound front it was no
contest; the iron sounded *much* better even when using an old TV
vertical output tranny as the choke.
I've got no idea how it measured; theoretically the bass should have
been grossly curtailed by the limited inductance of the VOT. it just
sounded better, with surprisingly adequate bass.
alan
- --
=========================================================================
From: James Melhuish <james@melhuish.org>
Subject: Re: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Thu, 23 Mar 2000 10:37:03 -0500
Source: Sound Digest Archive v02.n492
Hi Thorsten,
Your suggestion appears (to me) to be similar to Jack Elliano's
Ultrapath setup. See the schematic on the Xdrive (ultrapre.gif). He
ties a 35 to 50 uF oil cap from the bottom of the OPT directly to the
cathode. This return signal path bypasses the power supply entirely
(and the cathode bypass cap). He claims great sound from this. So it's
been done, no?
James
- --
James Melhuish
mailto:james@melhuish.org
http://melhuish.org
=========================================================================
From: David Home <DHome@creo.com>
Subject: RE: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Thu, 23 Mar 2000 10:22:15 -0800
Source: Sound Digest Archive v02.n493
I tried the ultra path trick on my #26 transformer coupled line amp.
Resulted in nasty NASTY buzz. Maybe with a indirectly heated cathode you can
get away with not having the filament AC tied to ground, but in particular
case it was bad. I put my BG back in and can live with its character for
now.
Regards, David
-----Original Message-----
From: T. Loesch [mailto:ezee_e@hotmail.com]
Sent: Thursday, March 23, 2000 8:57 AM
To: james@melhuish.org; sound@lists.io.com
Subject: Re: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Hi there,
>Your suggestion appears (to me) to be similar to Jack Elliano's
>Ultrapath setup. See the schematic on the Xdrive (ultrapre.gif).
Yes. It is. I have seen it practiced before in old radios and amplifiers
too.
>So it's been done, no?
Yes. We tried it with a 417A Transformer couled Pre.... We lost a quite a
nice Black Gate Cap.... The Improvemnet was neither subtle or ambigous.... I
hate electrolity Cap's. Even Black Gates and the better Elna's....
Then again, I prefer my custom Polyprop Cap in Aluminum Can's and potted
(deals with microphonics in cap's very effectively) over PIO.... But that's
a matter of taste.
Later T
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From: David Home <DHome@creo.com>
Subject: RE: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Thu, 23 Mar 2000 13:44:01 -0800
Source: Sound Digest Archive v02.n493
I use CCS heating as well and love it. However the filament needs to be AC
reference tied to ground through a cap or AC/DC coupled by using a fixed
bias on the grid.
Sorry if I was not clear. Regards, David
-----Original Message-----
From: T. Loesch [mailto:ezee_e@hotmail.com]
Sent: Thursday, March 23, 2000 10:51 AM
To: DHome@creo.com; james@melhuish.org; sound@lists.io.com
Subject: RE: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Hi there,
>I tried the ultra path trick on my #26 transformer coupled line amp.
>Resulted in nasty NASTY buzz. Maybe with a indirectly heated cathode
>you can get away with not having the filament AC tied to ground, but in
>particular case it was bad. I put my BG back in and can live with its
>character for now.
I have given up using AC heating with DH Valves.
I simply cannot get what I consider sufficiently low noise.... In my books
that is << 1mV on the Output of the Poweramp, Volume control at "normal
clipping level", MC Phono Input selected.
With DC (Constant Current Source Filaments), no problems.
Later Thorsten
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=========================================================================
From: "T. Loesch" <ezee_e@hotmail.com>
Subject: Re: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Thu, 23 Mar 2000 16:57:28 GMT
Source: Sound Digest Archive v02.n493
Hi there,
>Your suggestion appears (to me) to be similar to Jack Elliano's
>Ultrapath setup. See the schematic on the Xdrive (ultrapre.gif).
Yes. It is. I have seen it practiced before in old radios and amplifiers
too.
>So it's been done, no?
Yes. We tried it with a 417A Transformer couled Pre.... We lost a quite a
nice Black Gate Cap.... The Improvemnet was neither subtle or ambigous.... I
hate electrolity Cap's. Even Black Gates and the better Elna's....
Then again, I prefer my custom Polyprop Cap in Aluminum Can's and potted
(deals with microphonics in cap's very effectively) over PIO.... But that's
a matter of taste.
Later T
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=========================================================================
From: TubeGarden@aol.com
Subject: Re: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Thu, 23 Mar 2000 17:34:26 EST
Source: Sound Digest Archive v02.n493
In a message dated 3/23/00 12:00:15 PM US Mountain Standard Time,
ezee_e@hotmail.com writes:
> I have given up using AC heating with DH Valves.
Greets Jeets Neets!
I only use AC on the rectifier filaments.
No sense of adventure :)
Happy Ears!
Al B^}
=========================================================================
From: "T. Loesch" <ezee_e@hotmail.com>
Subject: RE: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Thu, 23 Mar 2000 18:51:01 GMT
Source: Sound Digest Archive v02.n493
Hi there,
>I tried the ultra path trick on my #26 transformer coupled line amp.
>Resulted in nasty NASTY buzz. Maybe with a indirectly heated cathode
>you can get away with not having the filament AC tied to ground, but in
>particular case it was bad. I put my BG back in and can live with its
>character for now.
I have given up using AC heating with DH Valves.
I simply cannot get what I consider sufficiently low noise.... In my books
that is << 1mV on the Output of the Poweramp, Volume control at "normal
clipping level", MC Phono Input selected.
With DC (Constant Current Source Filaments), no problems.
Later Thorsten
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From: =?iso-8859-1?q?Josef=20Aigner?= <josef_aigner@yahoo.com>
Subject: Re: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Thu, 23 Mar 2000 23:50:37 -0800 (PST)
Source: Sound Digest Archive v02.n493
Hi Joenetters
I tried the ultrapath setup on several occasions. The last time on my
26/45 transformer coupled amp. Everytime I got an improvement:
transparency, and a kind of air and ambience of the recording hall
(try it on several Carnegie Hall records...). This is the first trick
that improves the performance and costs less than the standard
lay-out. Did the same with my 417 line stage, the 71A line stage,
the 807SE, the 6SJ7/45 and now the 26/45.
Some quick thoughts, since I switched from the 6SJ7/45 to the 26/45.
1. Heat your DHT with constant current (see Manfred Hubers homepage,
thanks for answering silly questions...)
2. Use transformer coupling instead of caps. I modified the Athur
Loesch pre and changed the last stage to a Lundahl 1660 -> wow!
Lundahls interstages are as expensive as most of the audiophile caps,
so no excuses....
I made my first transformer-linestage one month before reciving the
SP-mag (inspired guess?). But Thomas Mayer's setup did the rest.
("There is no audio problem, that can't be cured with an additional
piece of iron...")
Josef
P.S. the Ultrapath circuit is also in the Radiotron Cunningham Manual
12 (I think or 11) dated 1934
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=========================================================================
From: tube@jump.net
Subject: Re: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Fri, 24 Mar 2000 09:28:02 -0600
Source: Sound Digest Archive v02.n494
"T. Loesch" wrote:
> Hi there,
>
> >Maybe a dumb question, but how is this ultrapath cap anything more than
> >just another (RC) filter stage on the power supply?
>
> Simple. Draw out the AC equivalent Circuit. With the Cathode Cap unbypassed
> the AC Path returning from the Anode to the Cathode of the valve includes
> this Capacitors and the Output Transformer, as well as the Valve, nothing
> else.
>
> Normally you have the PSU Capacitor (quite possibly a nasty, distorting
> electrolytic) and the Cathode Bypass Cap (another 'lytic?)in the AC Loop.
> "Ultrapath" provides a much cleaner "path" for the AC by using only one Cap
> and a rather high Quality, mosdest Value one.
[Snip]
Yup, the only way I have found to understand what happens here is to
view the parafeed choke as a current source, which it is at all but the
lowest frequencies. If the CS delivers a constant 1 A in, then that 1 A
MUST go out, somewhere. If the transformer/PF cap are tied to the
cathode, then the only two places it can go are thru the cathode
resistor and the grid. If the grid draws negligible current, then the
cathode resistor has a CONSTANT 1 A thru it, yielding a constant
voltage, with no need for a bypass cap. Tie the transformer/cap to
ground, however, and suddenly you need that bypass cap.
Also, the grid current is inherently at a much higher impedance than
the cathode, so it doesn't need a low impedance from cathode to ground.
In other words, for the grid, a normal cathode resistor can easily be
low enough already, with no need for a bypass. The fact that several
people here state that PF sounds better with no bypass cap or only a
high quality one suggests that it does not help the grid current to a
significant degree. Also, there will be fluctuations due to the main
power supply, and from the low frequency limitations of the choke,
both of which will tend to store energy in the bypass cap. If it is a
nasty electrolytic, then it will proceed to release this energy at
obnoxious times, messing up the sound. Since the grid doesn't need a
low impedance path, adding one via a bad cap will simply mess up the
sound.
Note, however, that this is the one case where a resistor (in the
cathode) may sound better than iron, because we do want at least a
medium impedance path for the grid. Of course, a small cap could take
care of this, leaving the cathode choke (in addition to a resistor)
to provide other benefits--whatever those might be!
Finally, let me disagree with the idea that PF adds a cap to the
signal path. In a normal SE design, the current flows thru the trans
to a power supply cap and eventually to ground. Parafeed simply MOVES
this cap to a different location! In both cases the current MUST flow
through a power supply cap. The only difference is that normally, a
cap must supply a low impedance path to ground for the amplifier AND
it must filter 120 Hz. In a parafeed, it simply has to supply the low
impedance path to ground, with no added filter duties.
People can say that parafeed has always been around, but contrary to
what Bob C. said, in RD4 it is shown only with a resistor, not a choke,
in the power supply lead. In practice, this is impossible to use for
power amps, due to the unbelievably high voltages and power dissipation
needed for the resistor. By coincidence, however, it was shown right
next to a figure of a regular amp with a choke load. Maybe the
juxtaposition of these two figures was what gave Mikey the idea? I will
say it again; my disagreements with "the Magnequest gang"
notwithstanding, parafeed is a FANTASTIC idea, and it simply would not
have occurred without Mike LeFevre pursuing it, period.
Phil Yates
=========================================================================
From: "T. Loesch" <ezee_e@hotmail.com>
Subject: RE: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Fri, 24 Mar 2000 10:23:29 GMT
Source: Sound Digest Archive v02.n494
Hi there,
>Maybe a dumb question, but how is this ultrapath cap anything more than
>just another (RC) filter stage on the power supply?
Simple. Draw out the AC equivalent Circuit. With the Cathode Cap unbypassed
the AC Path returning from the Anode to the Cathode of the valve includes
this Capacitors and the Output Transformer, as well as the Valve, nothing
else.
Normally you have the PSU Capacitor (quite possibly a nasty, distorting
electrolytic) and the Cathode Bypass Cap (another 'lytic?)in the AC Loop.
"Ultrapath" provides a much cleaner "path" for the AC by using only one Cap
and a rather high Quality, mosdest Value one.
Another trick is to leave the Cathode bypassed (but with a small Value
Resistor in Series with the Cap) and make the "Ultrapath" Cap to a size of:
C(u) = (1 + Mu) * C(k)
where C(u) is the Ultrapath Cap, C(k) the Cathode Bypass and Mu is the Mu of
the valve. This will significantly increase the PSRR of the Valve &
Transformer Stage as well as providing a high Quality, modest Value Cap to
complete the AC loop (at least above a few 100 hz).
Clearer?
Later Thorsten
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=========================================================================
From: "T. Loesch" <ezee_e@hotmail.com>
Subject: RE: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Fri, 24 Mar 2000 11:36:04 GMT
Source: Sound Digest Archive v02.n494
Darryl,
>There is still a resistor a power supply electro in parallel with the cap
>in the circuit you describe (and the rest of the power supply further back.
Yes and no.... Remeber, current flows allways the way of the least
resitance. The amount of AC Current flowing the "long way" through the PSU
and the various resiators) is very small compared to the amount flowing
through the "Ultrapath" Cap.... So small in fact that it can be safely
discarded in the context.
We have tried to measure it and there was little to measure at normal Audio
Frequencies.
>Same thing happens if you bypass the electrolytic in the power supply with
>a smaller better cap.
Not quite.
>I think it was you (I may be wrong) who recommended not just wiring the
>bypass cap straight across the electro, but to add a small series
>resistance to fight resonances between the two caps.
I do recommend this indeed. So do others.
>The output of the bypassed/filtered power supply is then the voltage acoss
>the bypass cap and this is where the output transformer connects. When you
>do this, it starts to look a lot like ultrapath, except for the cathode
>bypass cap of
>course, and your recommendations here would still apply.
Yes. However by placing the Ultrapath Cap we (can) eliminate the Cathode
Bypass Cap and we use one high quality Cap for the "whole" signal, rather
than a bypassed combo. It does sound better this way. A lot better.
>I'm not saying ultrapath won't work, I am just suggesting is sounds better
>for much the same reasons as those that account for the better sound of
>bypassed electro's in power supplies.
Yes, However it is a more effective way of "bypassing" as it indeed does
what it says, it makes the AC Signal current "bypass" (eg not flow through)
the PSU Cap (discounting a small redux....).
Again, draw up the equivalent AC Circuits (taking care to include all
relevant parasitics like ESR and ESL on the Cap's).... Then see what the
Impedance ratios left in the circuit are.
Later Thorsten
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=========================================================================
From: "T. Loesch" <ezee_e@hotmail.com>
Subject: Re: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Fri, 24 Mar 2000 13:46:24 GMT
Source: Sound Digest Archive v02.n494
Hello,
>What do you think, in a convencional output or PF, in the cathode,
>instead the cap+r // R that you proposed, use a LM317 as CS (or another
>CS) in series with a smaller R (or just the CS)?
We intend to try the CCS in a 2A3 PP Amplifier soon. We (London Live) have
been using Valve based (Penthodes) CCS's in the tail of output stages with
excellent success.
In SE Circuits I have not yet tried it. But how about another Choke in the
Cathode instead of a CCS? Why use sand if you can use Iron?
Later Thorsten
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From: "T. Loesch" <ezee_e@hotmail.com>
Subject: RE: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Fri, 24 Mar 2000 15:40:08 GMT
Source: Sound Digest Archive v02.n494
Gordon,
>If nothing else we are obsesive, who uses cheap caps.
Well, for starters, Darryl does... ;-)
I don't, of course.
>Second why not just fix bias the tube?
Yup. Or why not direct-couple to the preceeding gainstage, using eith the
Approach Komuro uses, my preferred approach or any other conceivable
option.... That fixes the Bias while we are at it.
There are many possible options. I was just highlighting a few specific
ones.
Later Thorsten
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From: "Darryl Lock" <dklock@ieee.org>
Subject: RE: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Fri, 24 Mar 2000 19:31:32 +1000
Source: Sound Digest Archive v02.n494
>
> Hi Joenetters
>
> I tried the ultrapath setup on several occasions. The last time on my
> 26/45 transformer coupled amp. Everytime I got an improvement:
> transparency, and a kind of air and ambience of the recording hall
> (try it on several Carnegie Hall records...). This is the first trick
> that improves the performance and costs less than the standard
> lay-out. Did the same with my 417 line stage, the 71A line stage,
> the 807SE, the 6SJ7/45 and now the 26/45.
>
Maybe a dumb question, but how is this ultrapath cap anything more than just
another (RC) filter stage on the power supply? Is it just another case of
bypassing the big electro's in the power supply with a better capacitor?
Darryl
=========================================================================
From: "Darryl Lock" <dklock@ieee.org>
Subject: RE: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Fri, 24 Mar 2000 20:54:59 +1000
Source: Sound Digest Archive v02.n494
> Hi there,
>
> >Maybe a dumb question, but how is this ultrapath cap anything more than
> >just another (RC) filter stage on the power supply?
>
> Simple. Draw out the AC equivalent Circuit. With the Cathode Cap
> unbypassed
> the AC Path returning from the Anode to the Cathode of the valve includes
> this Capacitors and the Output Transformer, as well as the Valve, nothing
> else.
There is still a resistor a power supply electro in parallel with the cap in
the circuit you describe (and the rest of the power supply further back.
Same thing happens if you bypass the electrolytic in the power supply with a
smaller better cap. I think it was you (I may be wrong) who recommended not
just wiring the bypass cap straight across the electro, but to add a small
series resistance to fight resonances between the two caps. The output of
the bypassed/filtered power supply is then the voltage acoss the bypass cap
and this is where the output transformer connects. When you do this, it
starts to look a lot like ultrapath, except for the cathode bypass cap of
course, and your recommendations here would still apply.
I'm not saying ultrapath won't work, I am just suggesting is sounds better
for much the same reasons as those that account for the better sound of
bypassed electro's in power supplies.
Darryl
=========================================================================
From: "J. Gordon Rankin" <waudio@cinti.net>
Subject: RE: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Fri, 24 Mar 00 09:36:07 -0500
Source: Sound Digest Archive v02.n494
>Simple. Draw out the AC equivalent Circuit. With the Cathode Cap unbypassed
>the AC Path returning from the Anode to the Cathode of the valve includes
>this Capacitors and the Output Transformer, as well as the Valve, nothing
>else.
>
>Normally you have the PSU Capacitor (quite possibly a nasty, distorting
>electrolytic) and the Cathode Bypass Cap (another 'lytic?)in the AC Loop.
>"Ultrapath" provides a much cleaner "path" for the AC by using only one Cap
>and a rather high Quality, mosdest Value one.
>
>Another trick is to leave the Cathode bypassed (but with a small Value
>Resistor in Series with the Cap) and make the "Ultrapath" Cap to a size of:
Thorsten,
If nothing else we are obsesive, who uses cheap caps.
Second why not just fix bias the tube?
Gordon
=====> Wavelength Audio <=====
mailto:waudio@cinti.net
http://www.WavelengthAudio.com
ph.fx. 513-271-4186 USA
=========================================================================
From: "P. de R. L." <triode@bow-tie.org.uk>
Subject: Re: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Sat, 25 Mar 2000 01:16:50 -0000
Source: Sound Digest Archive v02.n495
We've a great company in England; Mainline Surplus (includes Chester the
Cat)
I just bought a bag of capacitors for £5 (=$8US). Brilliant! For a start
there were 3 good-qulaity 220uf 450V caps plus loads of 200V Nichicons of
all sorts of values. I found Oscons in there too. there must be about
500capacitors all told - maybe more All the ones I've tried re=formed
really quickly..
Paul
- ----- Original Message -----
From: Darryl Lock <dklock@ieee.org>
To: <sound@lists.io.com>
Sent: Saturday, March 25, 2000 12:14 AM
Subject: RE: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
>
> >
> > Gordon,
> >
> > >If nothing else we are obsesive, who uses cheap caps.
> >
> > Well, for starters, Darryl does... ;-)
>
>
> Listen, this is not TNT-list so behave yourself!!! :-)
>
> I have been known to install film and foil orange drops, and use Nichicon
> caps in power supplies. Maybe not always to your exotic tastes, but not
> cheap either.
>
>
> Darryl
>
>
=========================================================================
From: "Darryl Lock" <dklock@ieee.org>
Subject: RE: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Sat, 25 Mar 2000 10:14:58 +1000
Source: Sound Digest Archive v02.n495
>
> Gordon,
>
> >If nothing else we are obsesive, who uses cheap caps.
>
> Well, for starters, Darryl does... ;-)
Listen, this is not TNT-list so behave yourself!!! :-)
I have been known to install film and foil orange drops, and use Nichicon
caps in power supplies. Maybe not always to your exotic tastes, but not
cheap either.
Darryl
=========================================================================
From: "T. Loesch" <ezee_e@hotmail.com>
Subject: Re: [JN] Paraffed - a bl%&$y Engineers view - Ultrapath?
Date: Mon, 27 Mar 2000 14:16:16 GMT
Source: Sound Digest Archive v02.n498
Hi there,
>That's very interesting because when I tried to connect my 46 driver (350v)
>B+ cap (100uF) to the cathode (at 130v) of my Loftin-White Shishido style
>driver circuit (26 DC to 46 driving 300B via IT on fixed bias)I got a slow
>oscillation.
You would. What you did was to remove the PSU decoupling (the PSU nos sees
the PSU Decoup Cap in series with the Cathode Resistor. The result - you
start the motorboat....
>This stopped when I connected it to ground and added a 220uF
>TSHA cahode R bypass cap. I am using a CC filament supply for the 46.
>
>Later I swapped the 100uF TSHA for a 8uF Dubilier (Wagga Wagga style