Sound Practices Mailing List Files - Volume 2
=========================================================================
From: StepHydro@aol.com
Subject: [JN] A2293/CV4079
Date: Tue, 29 Feb 2000 22:11:11 EST
Source: Sound Digest Archive v02.n470
In a message dated 02/29/2000 8:<BR55:<BR30 PM
Eastern Standard , retrovox@bigpond.com writes:
> I have a large quantity of A2293/CV4079 made by GEC/M-O Valve Co.
David,
Interesting valve. Are you in the USA? How much do you want for those? If
they are cheap tubes, I might like to have some "on spec" that they'd be
useful.
Cheers/Don Carron
=========================================================================
From: SBench@aol.com
Subject: [JN] A2 572-160 amp description up on my web page
Date: Thu, 3 May 2001 00:15:06 EDT
Source: Sound Digest Archive v02.n878
Hi All,
Modified the 841 A2 amp to use 572-160s. Increases power output
to 8 watts (with 490 volt supply). Interestingly, the distortion products
on this one are completely different than the 841 amp, even though the
front end is identical to the 841 front end. Very much A1 like in that the
primary distortion product is the second, with a little third, and almost no
higher order components. This one spends most of the time in positive
grid region. (Biased quiescent at +13 volts on the grid). Also higher
sensitivity (less than 0.5v produces 8 watts). Also reasonably quiet
(800 microvolts residual, mostly noise from the 8532s).
Note also to Kurt S. This amp has a 16 ohm output impedance (on the
8 ohm tap) providing a test of more current source like operation.
Like the 841 amp, very dynamic, and likes to be driven loud, with
almost totally invisible clip point. Gives the impression of a LOT
of reserve.
http://members.aol.com/sbench101
Direct access to this article is http://members.aol.com/sbench/a2part3.html
although you may want to access a2part2.html as well.
Best Regards,
Steve
=========================================================================
From: SBench@aol.com
Subject: [JN] A2 841 Amp
Date: Sun, 14 Jan 2001 22:14:23 EST
Source: Sound Digest Archive v02.n783
Hi All,
As I noted, had occasion to measure an 841 the other day. The curves
I obtained suggested it's possible to get 5 watts SE from one of those
critters.
The curves in A2 are pretty darn linear, and plate resistance is much more
constant than "normal". Sooo, I just had to cobble one of those things
together.
Operating point for the 841: 450V, 32 mA. (+7 volt bias with DC on the
filament). Decided to build the amp direct coupled: 8532/8532 differential
amp input; cathodes returned to -105V (0B2) via resistor. Plates 15k each
to +150V (0A2). 92V quiescent. Plate of input thru a 5651 gas tube/level
converter to a 6DJ8 cathode follower directly driving the 841 grid, and
also a 15k resistor to -105V (keeping current more or less constant).
This is probably not the simplest method, but what the heck.
841 requires about +11mA at +30V on the grid. This driver can swing
about +/- 35 volts WRT the +7V idle without too much effort.
Anyway..... The system, loaded with 10k (FS100) can produce about
7 watts at clip. The sound: Sounds GREAT. That's the reason for this
note. Clean, clear, dynamic. Reminiscent of my little 801 but much more
authority. I was pleasantly surprised by the sound quality. Also, dead
quiet. No hum, no hiss, no nothing except sound.
Experiments done with lab supplies. I'm going to have to build one of
these up as a "stand alone" system so I can compare it to a couple
others. Did I mention this thing sounds GREAT? From initial impressions,
this one may be a "keeper".
Conjecture: those constant resistance plate curves doing good things.
I'll probably try 400V and 37mA (+10v bias). Also have a lot of room to
experiment on the driver side. And, NOS 841's aren't that expensive
($28).
I think I might have mentioned, this thing sounds GREAT.
I'll put the 841 curves at
http://members.aol.com/sbench/841.gif
Best Regards,
Steve
=========================================================================
From: Ken Gilbert <ride5000@ride.ri.net>
Subject: Re: [JN] A2 841 Amp
Date: Mon, 15 Jan 2001 08:23:28 -0500
Source: Sound Digest Archive v02.n783
but steve, how does it SOUND?
;-)
kg
=========================================================================
From: SBench@aol.com
Subject: [JN] A2 SE 841
Date: Mon, 26 Mar 2001 20:54:26 EST
Source: Sound Digest Archive v02.n845
Hi Joes and Josies,
I sent this out last night, but never saw it appear so if it
did get posted, sorry for the duplicate......
Put up some schematics and descriptions of the 841 A2 5W SE
amp on my web pages. It actually sounds quite nice, and comes
alive at higher volumes.
direct access is http://members.aol.com/sbench/a2part2.html
or, of course via the front door (http://members.aol.com/sbench101)
What may also be of interest is the DC coupling, use of differential amp
input 8532) to eliminate the cathode bypass cap, and the individual
filtering on the power supplies. That's pretty effective: driving one
channel to clip and measuring hum+noise+crosstalk on the other
nets 84 dB s/n.
Best Regards,
Steve
=========================================================================
From: "Anya and Fred Humphrey" <afhumphrey@idirect.com>
Subject: Re: [JN] A2 SE 841
Date: Tue, 27 Mar 2001 08:15:16 -0500
Source: Sound Digest Archive v02.n845
Hi Steve,
I've been wishing for more A2 info the past few days. I just read this and
then followed it back to a2part1, and there it was. Thanks. A few questions:
1) Is the driver in d) basically what Shishido was calling an inverted
interstage transformer?
2) Is performance likely to be any better if the grid is kept positive at
all times?
3) Does A2 have any effect on lowering plate resistance? Specifically, is it
possible to use Eimac TH type triodes with real-world OP transformers?
Fred
- --- Original Message -----
From: <SBench@aol.com>
To: <sound@lists.io.com>
Sent: Monday, March 26, 2001 8:54 PM
Subject: [JN] A2 SE 841
> Hi Joes and Josies,
>
> I sent this out last night, but never saw it appear so if it
> did get posted, sorry for the duplicate......
>
> Put up some schematics and descriptions of the 841 A2 5W SE
> amp on my web pages. It actually sounds quite nice, and comes
> alive at higher volumes.
>
> direct access is http://members.aol.com/sbench/a2part2.html
>
> or, of course via the front door (http://members.aol.com/sbench101)
>
> What may also be of interest is the DC coupling, use of differential amp
> input 8532) to eliminate the cathode bypass cap, and the individual
> filtering on the power supplies. That's pretty effective: driving one
> channel to clip and measuring hum+noise+crosstalk on the other
> nets 84 dB s/n.
>
> Best Regards,
> Steve
>
=========================================================================
From: SBench@aol.com
Subject: Re: [JN] A2 SE 841
Date: Tue, 27 Mar 2001 22:12:22 EST
Source: Sound Digest Archive v02.n846
In a message dated 01-03-27 08:23:30 EST, afhumphrey@idirect.com writes:
> Hi Steve,
> I've been wishing for more A2 info the past few days. I just read this and
> then followed it back to a2part1, and there it was. Thanks. A few
questions:
> 1) Is the driver in d) basically what Shishido was calling an inverted
> interstage transformer?
Not sure, as I've not studied Shishido's work. Since there is current flowing
in the primary and secondary, there is some flux cancellation in that
method, though. The purpose of that interstage is to lower the driving Z
so that a "constant voltage" signal can be presented to the driven grid.
> 2) Is performance likely to be any better if the grid is kept positive at
> all times?
It *should* be, but practically, I have not found that to be the case. In the
test amp (841), the quiescent grid is +9 and with about 30 volt swing
in either direction [That is, to +39 and to -21 volts]. There is no particular
evidence of crossing between + and - biasing.
> 3) Does A2 have any effect on lowering plate resistance? Specifically, is
it
> possible to use Eimac TH type triodes with real-world OP transformers?
You do get a slight reduction of effective plate resistance, but it's a
small, not a large reduction. What you *do* get is a more constant
plate resistance over a larger output swing than is the case with A1
operation.
In the test amp, the effective output impedance is about 7.5 ohms(!)
When I convert it over to 572-160, I fully expect the output impedance
to be nearly 14 ohms with the same 10k to 8 ohm transformer.
Best Regards,
Steve
=========================================================================
From: "Wolfgang Braun" <wb@braunbaustoffe.de>
Subject: [JN] Aarhus
Date: Thu, 2 Aug 2001 08:09:51 +0200
Source: Sound Digest Archive v02.n939
have a save trip !!
see you tonight
Wolfgang
- --------------------------------------------------------------------------
Wolfgang Braun
Pleinfelderstr. 30
91166 Georgensgmuend
Germany
phone priv +49 9172 7937
phone fa +49 9172 70223
fax +49 9172 70270
mobile 0163 77 70223
wb@braunbaustoffe.de
wb7937@yahoo.de
- ----- Original Message -----
From: "evaguido" <EvaGuido@iaehv.nl>
To: <sound@lists.io.com>
Sent: Wednesday, August 01, 2001 8:30 PM
Subject: [JN] Quiet.....
> rather quiet before the Arhus storm .....
>
> Guido
>
>
=========================================================================
From: evaguido <EvaGuido@iaehv.nl>
Subject: [JN] Aarhus highlights
Date: Sat, 18 Aug 2001 20:35:00 +0200
Source: Sound Digest Archive v02.n949
Hi all,
Since I had a lot of work after returning from Denmark, I now found some
time to list some of the special things on the festival.
- - Very transparent and fast sounding OTL (the monster) though detail and
microdynamic lacking
- - Lively and precise sound from Remco's 1-bit CD player
- - Huge control of Timo's AKSA amps, over Berts' Woofers.
- - Big results for Manfreds - built in 30 hours only - CD player ! (and
neat preamp too!)
- - A giant step forwards for the Bahnsen horns (If I had a bigger living
room I still had to convince Eva but then....)
- - Bjorns' superspeakers with my beloved ceramic tweeters - well done !
- - "Kurts" EL84 based amps (built in the far east according his circuits!)
- - Remco's lecture on class D - very inspiring
- - Timo's Renault Kangoo, 15"" basshorn integrated :-)
- - Tempting rhythms by the Saturday night band
- - Manfreds' lecure and demo on power supplies. Unique moment to compare all
again (and I found out that Duncans' power supply designer includes stepped
current source loads)
- - Remco's direct driven ESL's showed dynamics and transparency - very high
potential !
- - Coherent sound from the huge (15") Jan Hass co-axial speakers
- - Borderpatrol 300b amp with good control on the speakers (lots of 300b's
lack control)
- - I am pretty sure I missed some more.......
- - But most of all, a wonderful organization (big thanks to Kurt & Karen!)
and a good time to meet you all.
many regards,
Guido & Eva
=========================================================================
From: Remco Stoutjesdijk <remco@ultranalog.com>
Subject: Re: [JN] Aarhus highlights
Date: Sat, 18 Aug 2001 21:25:56 +0200
Source: Sound Digest Archive v02.n949
Hi,
>- I am pretty sure I missed some more.......
Yeah - how about your own DAC? Best multibit sound I ever heard. You killed the sibilant 's' I found
so typical in multibit. There are many roads leading to Rome! (and some have the text of the stones
sanded off ;-))))
>- But most of all, a wonderful organization (big thanks to Kurt & Karen!)
>and a good time to meet you all.
Agreed 100%. Kudos to the *entire* crew!
Regards,
Remco
- --
http://www.ultranalog.com
=========================================================================
From: evaguido <EvaGuido@iaehv.nl>
Subject: Re: [JN] Aarhus highlights
Date: Sat, 18 Aug 2001 22:40:23 +0200
Source: Sound Digest Archive v02.n949
Hi Remco
I wrote
>>- I am pretty sure I missed some more.......
and then
Remco Stoutjesdijk wrote:
>Yeah - how about your own DAC? Best multibit sound I ever heard. You killed
>the sibilant 's' I found so typical in multibit. There are many roads
>leading to Rome! (and some have the text of the stones sanded off ;-))))
Thanks for your words. Yes, I noted for a while that most if not all
digital still distorts, and lacks detail (or DDR like Allen calls it)
best
Guido
>>- But most of all, a wonderful organization (big thanks to Kurt & Karen!)
>>and a good time to meet you all.
>
>Agreed 100%. Kudos to the *entire* crew!
>
>Regards,
>
>Remco
>--
>http://www.ultranalog.com
=========================================================================
From: Ralph & Diane Barone <barone@mdi.ca>
Subject: Re: [JN] Aarhus highlights
Date: Sun, 19 Aug 2001 11:22:19 -0700
Source: Sound Digest Archive v02.n950
Remco, when will the Class-D tutorial be available online?
Anxiously awaiting...
Ralph
PS: There was an interesting snippet in Electronics Design a month or so
ago in their "40 years ago" column. A certain Mr Shockley (name sound
familiar?) had built a solid state audio amplifier without any transistors.
It was based on two synchronized relaxation oscillators and used the audio
signal to bias one of the oscillators, which would cause it's phase to
shift relative to the other oscillator. A loudspeaker was then connected
across these two power oscillators. The "high frequency" (37 kHz)
oscillation was not reproduced by the loudspeaker, but the phase modulation
was, resulting in low-fi audio output. So it appears that the concept of a
Class-D audio amplifier with an H bridge outputs is at least 40 years old.
>Date: Sat, 18 Aug 2001 20:35:00 +0200
>From: evaguido <EvaGuido@iaehv.nl>
>Subject: [JN] Aarhus highlights
>
>Hi all,
>
>Since I had a lot of work after returning from Denmark, I now found some
>time to list some of the special things on the festival.
>
>- - Remco's lecture on class D - very inspiring
=========================================================================
From: Timo Christ <carnivor@uni-bremen.de>
Subject: Re: [JN] Aarhus highlights
Date: Sun, 19 Aug 2001 20:42:41 +0200
Source: Sound Digest Archive v02.n950
Hi Ralph, Remco,
Ralph & Diane Barone wrote:
>
> Remco, when will the Class-D tutorial be available online?
I'm waiting, too. :)
especially for the chronos design... ;))
> PS: There was an interesting snippet in Electronics Design a month or so
> ago in their "40 years ago" column. A certain Mr Shockley (name sound
> familiar?) had built a solid state audio amplifier without any transistors.
The diode guy Shockley? who invented J = Js * (exp(Uf/Vt)-1) ?
What kind of power oscillators did he use?
Timo
who's doing too much solid state physics at the moment
NP: 5 sterne deluxe
- --
/ /--' Timo Christ carnivore@uni-bremen.de
/ /<-. Electronics Engineering Student
__/ /__/ Horns 'r more fun:
' http://www-user.uni-bremen.de/~carnivor/
=========================================================================
From: Remco Stoutjesdijk <remco@ultranalog.com>
Subject: Re: [JN] Aarhus highlights
Date: Sun, 19 Aug 2001 22:06:47 +0200
Source: Sound Digest Archive v02.n950
>The diode guy Shockley? who invented J = Js * (exp(Uf/Vt)-1) ?
Mr. Shockley had a buddy called Bardeen. In 1949, they placed a triangular piece of Arsenic on a Ger
manium base (or the other way around...), which exhibited similar amplifying characteristics as the
vacuum tube...
The solid state age had started.
Actually, selenium's (more or less) rectifying characteristics had been discovered as early back as
the late 1800's. So, solid state was there first. Sorry...
I'll put the slides online as soon as I get a chance to steal, er... borrow the Acrobat software at
the university. Can't convert .ppt to .pdf at home.
But first: examns...
( Timo: cronos is high on my 2do list - my delay time indication turns out to be quite accurate... )
Regards,
Remco
- --
http://www.ultranalog.com
=========================================================================
From: Carter Hendricks <carter@i1.net>
Subject: [JN] RE: Aarhus highlights
Date: Mon, 20 Aug 2001 00:05:18 -0500
Source: Sound Digest Archive v02.n950
Remco wrote:
> Mr. Shockley had a buddy called Bardeen. In
> 1949...
47/48? Anyway in '72? we had an interview with
John Bardeen at the University of Illinois.
Jane Saxl and I were working on this liquid
crystal memory research proposal for Xerox and
we were sent to U of I to talk with Bardeen.
On the way there Joe Saxl asked if I'd had a
chance to look up this guy Bardeen and I told him
no but that I vaguely remembered... The interview
was going well, I thought, in that Bardeen would
change the subject about one question before I had
exhausted my feeble understanding. Then half way
through the interview I put together some of the
scans on his office wall and realized oh. That
John Bardeen. And of course he didn't have to ask
that one-more-question, and he was too nice to push
the matter.
--Carter
=========================================================================
From: "Paul Croft" <pcroft@iximd.com>
Subject: RE: [JN] Aarhus highlights
Date: Mon, 20 Aug 2001 19:54:58 -0400
Source: Sound Digest Archive v02.n951
Good luck on your exams, Remco!
Cheers,
Paul
> -----Original Message-----
> From: owner-sound@lists.io.com [mailto:owner-sound@lists.io.com]On
> Behalf Of Remco Stoutjesdijk
> Sent: Sunday, August 19, 2001 4:07 PM
> To: Timo Christ
> Cc: sound@lists.io.com
> Subject: Re: [JN] Aarhus highlights
snipped...
> borrow the Acrobat software at the university.
> Can't convert .ppt to .pdf at home.
> But first: examns...
>
> ( Timo: cronos is high on my 2do list - my delay time
> indication turns out to be quite accurate... )
>
> Regards,
>
> Remco
> --
> http://www.ultranalog.com
>
=========================================================================
From: Ralph & Diane Barone <barone@mdi.ca>
Subject: Re: [JN] Aarhus highlights
Date: Mon, 20 Aug 2001 20:26:38 -0700
Source: Sound Digest Archive v02.n952
>Date: Sun, 19 Aug 2001 20:42:41 +0200
>From: Timo Christ <carnivor@uni-bremen.de>
>Subject: Re: [JN] Aarhus highlights
>
>> PS: There was an interesting snippet in Electronics Design a month or so
>> ago in their "40 years ago" column. A certain Mr Shockley (name sound
>> familiar?) had built a solid state audio amplifier without any transistors.
>
>The diode guy Shockley? who invented J = Js * (exp(Uf/Vt)-1) ?
>
>What kind of power oscillators did he use?
If I recall correctly (silly me, forgot to photocopy the article), it used
tunnel diodes or something of that ilk.
>Timo
>who's doing too much solid state physics at the moment
>NP: 5 sterne deluxe
>- --
> / /--' Timo Christ carnivore@uni-bremen.de
> / /<-. Electronics Engineering Student
>__/ /__/ Horns 'r more fun:
> ' http://www-user.uni-bremen.de/~carnivor/
>
=========================================================================
From: rfrancis@glasscity.net
Subject: [JN] Aarhus Info on the web
Date: Mon, 10 Jul 2000 06:01:02 -0700
Source: Sound Digest Archive v02.n600
Fellow travelers:
Found a great site with info in English:
http://www.aarhus-tourist.dk/engelsk/frameset.html
Looks like there is a substantial amount of live music and nightlife!
Too bad we'll just miss the Int'l Jazz Festival there...
If you're into prehistory, check out the Runic stone at the bottom
here:
http://prehistory.moes.hum.aau.dk/fhm/udste.htm
It seems I may not have looked hard enough to find a great rental
car deal from Germany, as some Joesters responded privately with
interesting suggestions. I'll post info if anyone is interested.
Rick Francis
- -----
Sent using MailStart.com ( http://MailStart.Com/welcome.html )
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=========================================================================
From: "=?ISO-8859-1?Q?Torbj=F8rn_Lien?=" <mdrivekl@online.no>
Subject: [JN] : Aarhus Rangers
Date: Tue, 29 May 2001 01:08:44 +0200
Source: Sound Digest Archive v02.n894
Hello all.
This is my first posting to the list since long time,-.
As things seems to be easening up alittle these days,
I'll try to find time for something Audio,-
(yes, and for you Timo C and Paul B...:)
This summer I'll try to get to visit Kurt and the triodefestival in Aarhus.
But since living "in transit" so to speak, I'll not be contributing with
much. Anyway, If things proceed as planned, I thought about bringing
some of my one-way speaks for fun listening, and wonder if
there are others that might contemplate on the same thing?
Some (long) time ago I got an email from a German-joe that would try to
bring his Triangle speaks. Could be interresting, I never laid ears to
these,-
I myself could try to bring my mildly tweaked 755C's, Axiom-80's, and
maybe,-..well Bert, I'll see what I manage...;)
(There are afew of you that know me as 'the' collector of aluminium
wired voicecoils, and thanks to two marvellous gentlemen on this list;
Bert Doppenberg and Paul Butterfield I'll be able to realize afew
more personal creations...but unsure if able before summer..)
I would have to get together atleast one pair of cabs as my units are
at present unboxed. I wonder: Anyone else listening to the 755's or
the 80's here in Europe? Would these someone take the trouble to
havl their creations to Aarhus?
It would be very convenient for me if any other joe could bring his
completed constructions with their (maybe stock-version of the) 755C
or Ax.80. Then we could simply swap between the units in the
same enclosure to notify possible differences, and it would save me
from cab-work I really dont have time to do properly before summer.
I havent heard my units on a good setup for a very long time,
so it could be great fun and maybe of interrest for other visiting
joe's too..?
Regards
Torbjorn, Norway
>
>
>
>
=========================================================================
From: TubeGarden@aol.com
Subject: Re: [JN] abnormal hearing
Date: Fri, 31 Dec 1999 00:22:20 EST
Source: Sound Digest Archive v02.n380
Greets Jeets Neets,
I have developed a 'third ear'.
My upper lip and front teeth seem to be hardwired to my aural processor.
I didn't notice until I got an electric razor last month.
Listening to my system, I get much better sound when I smile.
Happy New Ear!
Al B^}
=========================================================================
From: "PEARL Cust Serv" <custserv@pearl-hifi.com>
Subject: [JN] A Boss Is . . .
Date: Wed, 29 Dec 1999 08:00:54 -0700
Source: Sound Digest Archive v02.n374
Hi All:
All too often - and often with good cause - bosses get a bad rap. So
here's what looks to me like a pretty clear headed view from the other side
of the desk
Bill - PEARL, Inc.
=======================================
What is a Boss . . . .
A Boss is someone who can say to himself every morning: "I am my own
boss. I can run my business as I please. No one can tell me what to do."
(It is always good to begin the day with a big laugh).
A Boss is a capitalist and an entrepreneur, which means that he has as
much right to go broke as to make a profit.
A Boss is a fellow who can work as hard and as long as he likes or as
little as he likes -- depending on how much he would like to keep on being a
boss.
A Boss can tell people who work for him what to do and how and when to
do it--and then he can ask them why they didn't.
A Boss always has lots of people to talk to--people who want to sell him
things, people who want him to give things, people who want to complain
about things, people who want to do things, people who want him to pay
for things.
A Boss has the opportunity to become a Ph.D. in merchandising,
advertising, accounting, finance, engineering, psychology, technology,
communications, supervision, economics, public relations and human
relations.
A Boss can hire and fire people any time he likes--subject to various
laws, regulations, bureaucrats, union agents, inspectors, judges and
public officials.
A Boss has the privilege of collecting and handling a lot of money for
the government--without any mistakes.
A Boss has the right to worry about his business 24 hours a day--and
usually has pretty good reasons.
A Boss is a guy who has all of his money--and probably quite a lot
more--tied up in his business.
A Boss is someone who is not very likely to see much of his family or
friends.
A Boss has the fun of trying to guess which of 500 or more new products
will sell in his store--and trying to figure out why he was wrong.
A Boss is the only one in the business who can go on vacation any time
and stay as long as he likes and hardly ever does.
A Boss is the guy who has the right to make all the tough decisions--as
long as he is right about 95% of the time
=========================================================================
From: MHenry7868@aol.com
Subject: [JN] about cd pro module
Date: Thu, 28 Sep 2000 12:39:53 EDT
Source: Sound Digest Archive v02.n677
<< That's $470.00 USD. Does that include VAT?
How does it sound? Are you using the on board DAC?
Do you have a price list on the complete offering from DAISy?
Peter C
>>
to know everything about the cd pro module, you must first ask a password to
Nico Thevissen (tell him who you are with few words)
teafish@planet.nl
and then go to
http://www.daisy-laser.nl/homeoptics/
after listen to it for 2 hours, i am now sure that there is a problem in my
power supply : lack of bass, sound not very relaxed, like my 721 when it is
powered by AC line.
actually it sounds like a big brother of the 721. good, but i prefer the
punch of burr-brown converters.
- --------- Marc HENRY, Saint Helen, FRANCE -----
=========================================================================
From: evaguido <EvaGuido@iaehv.nl>
Subject: Re: [JN] about cd pro module
Date: Fri, 29 Sep 2000 09:31:12 +0200
Source: Sound Digest Archive v02.n678
give it at least week to warm up; it is digital equipment
=
Guido
>after listen to it for 2 hours, i am now sure that there is a problem in my
>power supply : lack of bass, sound not very relaxed, like my 721 when it is
>powered by AC line.
>actually it sounds like a big brother of the 721. good, but i prefer the
>punch of burr-brown converters.
>
>--------- Marc HENRY, Saint Helen, FRANCE -----
>
>
=========================================================================
From: "T. Loesch" <ezee_e@hotmail.com>
Subject: Re: [JN] about cd pro module
Date: Fri, 29 Sep 2000 11:09:44 GMT
Source: Sound Digest Archive v02.n678
Hi,
>to know everything about the cd pro module, you must first ask a password
>to Nico Thevissen (tell him who you are with few words)
>teafish@planet.nl
>and then go to
>http://www.daisy-laser.nl/homeoptics/
Actually, knowing the Javascript that does the "Password Protection" the
password is the same all the time, at the moment it is the name of the guy
who said "open sesame"....
Later T
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http://profiles.msn.com.
=========================================================================
From: Grover Gardner <groverg@postoffice.att.net>
Subject: [JN] About Face!
Date: Tue, 17 Aug 1999 20:11:02 -0400
Source: Sound Digest Archive v02.n250
Interesting experience this morning. Someone on RAT asked about SE kits,
mentioning the Bottlehead ones in particular and saying he wanted a really
smooth sound with lots of detail on top. I suggested he might like the the
B-Glow, with the C4S current-source boards for the driver tube. I tried the
DIY version of this gadget published in Valve maybe a year ago, thought it was
really cool but a little more of that "you-know-what" sound than I wanted at
the time. So today I write this post and then look over and there on my desk
is a little bag of spare parts I ordered back when, thinking I was sure to
blow up a few until I got it right. So as I'm loving the 845, the 10Y driver
and the triode-wired 6686 input stage, but yearning for just an eensy-weensy
bit more gain to get the dynamics right, and just a teense more control and
top end extension, I thought, Hey! Why not? The 6686 is running at 10mA,
about 150 Vp--perfect!
So I wire these things together, looks like a spider's nest, you know, hook it
up and... Geez! What was I thinking before? "Shucks, the disortion's too
low", or "Aw, this thing has too much bandwidth"?
It's just about exactly what I wanted. It's still a touch glossy, but I think
some better-than-average parts would clean it up. Also, I think my goals are
a little different now, and I'm more comfortable with small trade-offs here
and there. Thought I'd toss it out since nobody's mentioned these things
lately, and thinking of ol' Doc makes me nostalgic. I'll have to pop for a
couple of those little kits he makes, I think they snazzed them up a lot.
- --
Grover Gardner
groverg@postoffice.att.net
=========================================================================
From: Jeremy Epstein <jepstein@shwd.com>
Subject: JOENET About the Archive
Date: Wed, 20 Jan 1999 12:20:35 -0500
Source: Sound Digest Archive v02.n003
I was told by the helpful helpers at the help desk of io.com, that the
display of the archive (last-first or first-first) depends on the
REQUESTING computer, the "ftp client" as they put it.
Anybody know any more about this? My "ftp client" software is Netscape,
I don't see any way to change this in the software options, but maybe it
can be changed with the URL you use to point to the ftp site?
- -j
- --
=====================================
Jeremy Epstein .... jepstein@shwd.com
=====================================
=========================================================================
From: Steve Fellini <steve@helix.nih.gov>
Subject: Re: JOENET About the Archive
Date: Wed, 20 Jan 1999 12:46:38 -0500 (EST)
Source: Sound Digest Archive v02.n003
Date: Wed, 20 Jan 1999 12:20:35 -0500
From: Jeremy Epstein <jepstein@shwd.com>
I was told by the helpful helpers at the help desk of io.com, that the
display of the archive (last-first or first-first) depends on the
REQUESTING computer, the "ftp client"
Using the 'ftp' _program_ as your ftp client you could say 'ls -t' to
get files with the latest timestamp first, or 'ls -tr' to reverse the
order, ie latest timestamp last.
I'm not sure you'd have much control over this with a browser as your
ftp client.
=========================================================================
From: longrie@mmace.nrl.navy.mil
Subject: [JN] about the cathode interface
Date: Fri, 31 Mar 2000 11:13:22 +0100
Source: Sound Digest Archive v02.n505
Hi Chris,
Very interesting subject. The cathode interface was a very
big deal to the tube manufacturers during the twilight of
their era. Just how important was firmly established by
Bell Labs in their early 60's R&D for their undersea sytems.
These undersea transoceanic cables had built-in repeaters
with vacuum tube amplifiers. Servicing these tubes would not
be an option. They had to work for a design life measured in
decades.
So, through their investigations, Bell Labs became quite
knowledgeable on tube reliability factors. Turns out that there
are two main mechanisms of normal aging in an oxide cathode tube.
There are plenty of other failure mechanisms, but just two *normal*
aging processes.
One is barium depletion from the oxide. Barium has a ready
supply of low-work-function free electrons. When the barium
content dwindles in the oxide, the work function shoots up higher,
and it becomes much harder for electrons to escape the cathode.
The low work function property of barium that makes it valuable
as an emitter also makes it chemically active. It tends to
react with impurities and stay bound up that way. It can vaporize
and plate out upon the tube structures.
Two is the growth of this cathode interface. This is the
interface layer between the snowy white oxide and the (normally)
nickel sleeve. Over the life of the tube, a slow chemical
reaction takes place here wherein the trace impurities in both
the oxide and the nickel combine to form this resistive interface.
A new tube already has an interface resistance of 10 ohms or so.
Over the tube lifetime, in a normal production tube, this resistance
grows to numbers like 500 or 1000 ohms. Much worse in special cases.
500 or 1000 ohms internally in a tube seriously disrupts the
transconductance, limiting the emissions. There are other effects.
There grows a rectifying effect across this interface. And there
grows a capacitance in series with the plate to cathode path.
It is interesting that Bell Labs identified and studied these
phenomena by using their recently developed semiconductor techniques.
After all, they had invented the transistor just 12 or so years
earlier and that kind of diagnostic thinking made the tube cathode
interface study possible.
Wouldn't you just know it though. The oxide cathode in a tube
can be thought of as a kind of bulk semiconductor. And it is this
semiconductor that fails in the tube.
As for those AT&T undersea tubes, they are *still* working,
some 40 years or 300,000+ hours later!
So, to relate all of this to Tektronix scopes. If the tubes in
a scope start drifting and changing their properties, then those
scopes start drifting out of calibration. This effect happens to
all tube equipment, not just Tektronix. But I take exception to
a couple of the comments attributed to Stan Griffiths book. There
isn't any way to directly check on the cathode interface. You
check your tube for emissions. When emissions slowly decline, you
know the cathode interface is building up. Nothing you can do
about it. As to his comment about this occuring primarily in cut off
tubes, does he really mean to imply that tubes left running won't
age and grow weaker? This is simply not so.
regards
gary
>Date: Sat, 25 Mar 2000 21:08:10 -0600
>From: Chris and Susan Beck <n9zes@execpc.com>
>Subject: [JN] Tek scope - cathode interface??
>
>I was reading Stan Griffiths' book "Ocilloscopes - Selecting and
>Restoring a Classic" tonight. What an interesting read, and Tektronix
>was and is quite a company. He makes a big point of checking for
>"cathode interface" on the scopes. Is this really an issue?? I've not
>heard of anyone else mention it, and from what I've read, this problem
>occurs primarily in tubes where there is no current flowing for long
>periods, such as computers where the tubes are cut off.
>
>I did notice the "spike" on the leading edge of the square waves today
>that Stan says is indicative of the problem, but that could be due to my
>voltage problem. Now, since I'll be primarily looking at low frequency
>stuff (audio), is it a problem even if it is present? I really don't
>feel like retubing the plugin, the vertical amp, and then having to
>recalibrate the beast.
>
>Thanks!
>
>Chris
>
=========================================================================
From: Bob Danielak <robert.m.danielak@lmco.com>
Subject: Re: [JN] about the cathode interface
Date: Mon, 01 Jan 1996 01:02:28 -0500
Source: Sound Digest Archive v02.n506
one reason is because the "military" communications satellite systems are
pitifully slow
(at least the one's i'm allowed to know about......;) )
bob.d.
- ----- Original Message -----
From: "Joseph Robertson" <joerbus@mindspring.com>
To: <longrie@mmace.nrl.navy.mil>; <sound@lists.io.com>
Sent: Friday, March 31, 2000 11:58 AM
Subject: Re: [JN] about the cathode interface
> Thanks,Gary,very interesting post.I've wondered if those undersea amps
> were
> still in use what with satellite communications and all-I bet the lines
> are
> less cluttered with phone traffic now.Of course,the Navy's got all those
> sub
> detecteing arrays all over the place,so those lines are well monitored!
>
> Smiles,
> Joe Robertson
=========================================================================
From: Dan Kerl <dlkerl@ro.com>
Subject: Re: [JN] about the cathode interface
Date: Fri, 31 Mar 2000 10:07:50 -0600
Source: Sound Digest Archive v02.n506
Thanks for the excellent post concerning cathode interface, Gary.
<snip>
> A new tube already has an interface resistance of 10 ohms or so.
> Over the tube lifetime, in a normal production tube, this resistance
> grows to numbers like 500 or 1000 ohms. Much worse in special cases.
> 500 or 1000 ohms internally in a tube seriously disrupts the
> transconductance, limiting the emissions.
> So, to relate all of this to Tektronix scopes. If the tubes in
> a scope start drifting and changing their properties, then those
> scopes start drifting out of calibration. This effect happens to
> all tube equipment, not just Tektronix. But I take exception to
> a couple of the comments attributed to Stan Griffiths book. There
> isn't any way to directly check on the cathode interface. You
> check your tube for emissions. When emissions slowly decline, you
> know the cathode interface is building up. Nothing you can do
> about it. As to his comment about this occuring primarily in cut off
> tubes, does he really mean to imply that tubes left running won't
> age and grow weaker? This is simply not so.
From what I gather from Stan's book, it is the aforementioned reduction
in Gm that limits the high frequency response of the amplifiers in the
scope. This is apparently observable when the scope in question fails
to meet it HF response specs, causing artifacts to appear in the
waveform.
Quote from W7NI Stan Griffiths (old Boatanchors post from 1996), in response
to a question about a 585A unit-
- ----------------------------------------------------------------------------
I am not aware of any test fixture that allows you to test a single tube for
cathode interface. You can, of course, test the whole system, scope and
plugin, for cathode interface by feeding in a fastrise squarewave and making
sure the scope displays it without what appears to be gradual spiking on the
leading edge. If you don't have cathode interface, you are done with the
test. If you do have it, you now have to figure out if it is in the
mainframe or the plugin, which is where the 84 comes in. The 84 will not
have cathode interface so if you see it in the display while using to 84 to
provide a fastrise squarewave, you know it is in the mainframe.
I experimented awhile back with cathode interface in CA plugins. A CA uses
a pair of 6AU6s and a pair of 12AU6s in each channel and all 8 of those
tubes are subject to cathode interface. I found one of my CAs that was free
of cathode interface and plugged in a few unknown 6AU6s and 12AU6s one at a
time to see if I could tell if individual tubes had cathode interface. Yes,
I could tell. A single tube with serious cathode interface shows up pretty
obviously. When I was a service tech for Tek back in the mid-60s, if we had
any indication of cathode interface in a CA, we just retubed the whole thing
and that fixed it. I am sure it was a good decision at the time. Tubes
were cheaper than labor so it didn't make sense to try to save one tube.
Nowdays, it makes sense to me to check each tube individually and I have
three boxes of 6AU6s and 12AU6s marked "cathode interface", "no cathode
interface", and "unknown".
One of the problems with cathode interface is that it is like tube emission
in that there is no definite black and white line defining when a tube has
it or does not have it. A tube may have a little of it or a lot of it and
you have to decide when it is too much. Very subjective. One thing we do
know is there is no known way to reverse it so once a tube has it, it has it
forever. Another thing we know is that certain circuits don't care if the
tubes in them have cathode interface or not so tubes with cathode interface
still have some value which is why I save them in a separate box.
- ----------------------------------------------------------------------------
- --
Dan Kerl
dlkerl@ro.com
=========================================================================
From: "jc morrison" <jcm@sovtek.com>
Subject: Re: [JN] about the cathode interface
Date: Fri, 31 Mar 2000 11:19:52 -0500
Source: Sound Digest Archive v02.n506
hey gary,
actually, it is precisely those tubes (with the common impurities) that are
operated for long periods in cutoff that are the biggest offenders. the
situation that hipped the government (via raytheon) and *hence* western
electric/bell labs, was the experience encountered with the MK47analog
computer for MK68 gunfire control system and the TRW 602 mainframe computer.
both were used to perform math functions (trig for gun directing and the
first spreadsheet, used for tracking military oil stocks) and both suffered
from tube failures due to cathode interface. the tubes were operated for
long periods in cutoff (with the filaments lit) and the dual triodes were
particularly susceptable (one tube cutoff and one driving a synchro or
another logic module...). the 5751, 5814 and 6005 were specifically
developed to address the problem. but you are right that the change in work
function and the rectification effects are the symptoms specific to cathode
interface. the effect *can* clearly be seen in 500 series tek oscopes... i
have had the pleasure of spending time with george muckenstrom, head of
calibration at tek through that period (he started connecticut calibration
inc....) and i assure you it was a big deal. raytheon never mentioned any of
their difficulties to anyone outside of the business and were silent when
tek started having problems. it was a BIG deal for tek and it severely
affected sales and service for two years.
jc
=========================================================================
From: "Joseph Robertson" <joerbus@mindspring.com>
Subject: Re: [JN] about the cathode interface
Date: Fri, 31 Mar 2000 11:58:58 -0500
Source: Sound Digest Archive v02.n506
Thanks,Gary,very interesting post.I've wondered if those undersea amps were
still in use what with satellite communications and all-I bet the lines are
less cluttered with phone traffic now.Of course,the Navy's got all those sub
detecteing arrays all over the place,so those lines are well monitored!
Smiles,
Joe Robertson
- ----- Original Message -----
From: <longrie@mmace.nrl.navy.mil>
To: <sound@lists.io.com>
Sent: Friday, March 31, 2000 5:13 AM
Subject: [JN] about the cathode interface
> Hi Chris,
>
> Very interesting subject. The cathode interface was a very
> big deal to the tube manufacturers during the twilight of
> their era. Just how important was firmly established by
> Bell Labs in their early 60's R&D for their undersea sytems.
> These undersea transoceanic cables had built-in repeaters
> with vacuum tube amplifiers. Servicing these tubes would not
> be an option. They had to work for a design life measured in
> decades.
> So, through their investigations, Bell Labs became quite
> knowledgeable on tube reliability factors. Turns out that there
> are two main mechanisms of normal aging in an oxide cathode tube.
> There are plenty of other failure mechanisms, but just two *normal*
> aging processes.
> One is barium depletion from the oxide. Barium has a ready
> supply of low-work-function free electrons. When the barium
> content dwindles in the oxide, the work function shoots up higher,
> and it becomes much harder for electrons to escape the cathode.
> The low work function property of barium that makes it valuable
> as an emitter also makes it chemically active. It tends to
> react with impurities and stay bound up that way. It can vaporize
> and plate out upon the tube structures.
> Two is the growth of this cathode interface. This is the
> interface layer between the snowy white oxide and the (normally)
> nickel sleeve. Over the life of the tube, a slow chemical
> reaction takes place here wherein the trace impurities in both
> the oxide and the nickel combine to form this resistive interface.
> A new tube already has an interface resistance of 10 ohms or so.
> Over the tube lifetime, in a normal production tube, this resistance
> grows to numbers like 500 or 1000 ohms. Much worse in special cases.
> 500 or 1000 ohms internally in a tube seriously disrupts the
> transconductance, limiting the emissions. There are other effects.
> There grows a rectifying effect across this interface. And there
> grows a capacitance in series with the plate to cathode path.
> It is interesting that Bell Labs identified and studied these
> phenomena by using their recently developed semiconductor techniques.
> After all, they had invented the transistor just 12 or so years
> earlier and that kind of diagnostic thinking made the tube cathode
> interface study possible.
> Wouldn't you just know it though. The oxide cathode in a tube
> can be thought of as a kind of bulk semiconductor. And it is this
> semiconductor that fails in the tube.
> As for those AT&T undersea tubes, they are *still* working,
> some 40 years or 300,000+ hours later!
> So, to relate all of this to Tektronix scopes. If the tubes in
> a scope start drifting and changing their properties, then those
> scopes start drifting out of calibration. This effect happens to
> all tube equipment, not just Tektronix. But I take exception to
> a couple of the comments attributed to Stan Griffiths book. There
> isn't any way to directly check on the cathode interface. You
> check your tube for emissions. When emissions slowly decline, you
> know the cathode interface is building up. Nothing you can do
> about it. As to his comment about this occuring primarily in cut off
> tubes, does he really mean to imply that tubes left running won't
> age and grow weaker? This is simply not so.
>
>
> regards
>
> gary
>
>
>
>
>
>
> >Date: Sat, 25 Mar 2000 21:08:10 -0600
> >From: Chris and Susan Beck <n9zes@execpc.com>
> >Subject: [JN] Tek scope - cathode interface??
> >
> >I was reading Stan Griffiths' book "Ocilloscopes - Selecting and
> >Restoring a Classic" tonight. What an interesting read, and Tektronix
> >was and is quite a company. He makes a big point of checking for
> >"cathode interface" on the scopes. Is this really an issue?? I've not
> >heard of anyone else mention it, and from what I've read, this problem
> >occurs primarily in tubes where there is no current flowing for long
> >periods, such as computers where the tubes are cut off.
> >
> >I did notice the "spike" on the leading edge of the square waves today
> >that Stan says is indicative of the problem, but that could be due to my
> >voltage problem. Now, since I'll be primarily looking at low frequency
> >stuff (audio), is it a problem even if it is present? I really don't
> >feel like retubing the plugin, the vertical amp, and then having to
> >recalibrate the beast.
> >
> >Thanks!
> >
> >Chris
> >
>
=========================================================================
From: SBench@aol.com
Subject: Re: [JN] about the cathode interface
Date: Fri, 31 Mar 2000 12:17:53 EST
Source: Sound Digest Archive v02.n506
In a message dated 00-03-31 11:48:43 EST, joerbus@mindspring.com writes:
<< Thanks,Gary,very interesting post.I've wondered if those undersea amps were
still in use what with satellite communications and all-I bet the lines are
less cluttered with phone traffic now.Of course,the Navy's got all those sub
detecteing arrays all over the place,so those lines are well monitored!
>>
Hi All,
Interestingly enough, some of those connections are more desireable
than satellite connection. Reason: Echo. The delay via a bird is
higher than thru the cable, making more exotic use of echo cancellers.
For data traffic, OTOH, not an issue.
Best Regards,
Steve
=========================================================================
From: longrie@mmace.nrl.navy.mil
Subject: Re: [JN] about the cathode interface
Date: Fri, 31 Mar 2000 14:09:49 +0100
Source: Sound Digest Archive v02.n506
Hi JC,
It was nice to hear those anecdotes. I think we are really
on the same page in most or all of this. I offer a couple
of comments, re-emphasisings (reemphasises?), and queries.
a comment: The increase in cathode work function would most
directly be a symptom of barium depletion. Yeah, I know,
some of that depleted barium probably got bound up in the
interface too. Most of it got plated out in the tube. That
which gives barium a low work function also gives it a
high vapor pressure. So it tends to vaporize much more
readily than, say, tungsten.
reiterations: We know that tube emissions grow feeble over
the lifetime of the tube. This is due to both the barium
depletion and the cathode interface buildup. These aging
processes occur in the presence of heat. Vacuum tubes can
work just fine after a shelf life of decades. JC establishes
anecdotally that tubes operated for long periods under
cutoff (no plate current) conditions can suffer from
accelerated cathode interface buildup.
reiteration: The symptoms of cathode interface buildup are
weakening emissions, increased series resistance, reduced
transconductance, growing rectification, and growing
capacitance.
Question: Bell Labs found that two factors contributed towards
long lifetimes of tubes. One is to operate at reduced temperature.
Isn't this one of Newton's Laws? Things go bad under temperature
and pressure? The other thing was to use ultra, ultra, *ultra*
pure materials in the nickel and oxide cathode construction.
No impurities, no cathode interface.
Sooo, what does this suggest to us about the 5751, 5814 and 6005?
Do you have a feel for the characteristics of these three? Are
they known to be run at cooler operating points? Is the heater
power reduced from their counterparts? Are they know to have an
unusually long lifetime? I am guessing that some of these answers
will be positive.
Question: I am wondering what the physical electronic mechanism
might be that would account for cut off tubes ageing more
rapidly. Maybe there is an obvious reason. I speculate that
tubes run in cutoff have higher cathode temperatures. The same
tube with a plate current has the benefit of lower cathode
temperature by electron cooling. Assume the same heater voltage
for each case. What do you think about that? JC? Eggs?
regards and respects
gary
At 11:19 AM 3/31/00 -0500, you wrote:
>hey gary,
>actually, it is precisely those tubes (with the common impurities) that are
>operated for long periods in cutoff that are the biggest offenders. the
>situation that hipped the government (via raytheon) and *hence* western
>electric/bell labs, was the experience encountered with the MK47analog
>computer for MK68 gunfire control system and the TRW 602 mainframe computer.
>both were used to perform math functions (trig for gun directing and the
>first spreadsheet, used for tracking military oil stocks) and both suffered
>from tube failures due to cathode interface. the tubes were operated for
>long periods in cutoff (with the filaments lit) and the dual triodes were
>particularly susceptable (one tube cutoff and one driving a synchro or
>another logic module...). the 5751, 5814 and 6005 were specifically
>developed to address the problem. but you are right that the change in work
>function and the rectification effects are the symptoms specific to cathode
>interface. the effect *can* clearly be seen in 500 series tek oscopes... i
>have had the pleasure of spending time with george muckenstrom, head of
>calibration at tek through that period (he started connecticut calibration
>inc....) and i assure you it was a big deal. raytheon never mentioned any of
>their difficulties to anyone outside of the business and were silent when
>tek started having problems. it was a BIG deal for tek and it severely
>affected sales and service for two years.
>jc
>
>
>
>
"Men wanted for hazardous journey, small wages, bitter cold,
long months of complete darkness, constant danger, safe return
doubtful. Honour and recognition in case of success."
----- Sir Ernest Shackleton
=========================================================================
From: longrie@mmace.nrl.navy.mil
Subject: Re: [JN] about the cathode interface
Date: Fri, 31 Mar 2000 14:14:59 +0100
Source: Sound Digest Archive v02.n506
Hey Joe,
Well, I know about the trans Pacific line. It is now in use by
the University of Hawaii. They raked it up from the seabed in
recent years and connected it to their undersea seismic sensor
system. So it is being put to good scientific use.
There was an article on this in the New York Times, am guessing
maybe August 99. Does anyone have access to the NYT Archives?
There are numerous articles on this undersea system and the
special tubes in the Bell Labs Technical Journal. Look around
in the early 60's.
regards
gary
At 11:58 AM 3/31/00 -0500, you wrote:
>Thanks,Gary,very interesting post.I've wondered if those undersea amps were
>still in use what with satellite communications and all-I bet the lines are
>less cluttered with phone traffic now.Of course,the Navy's got all those sub
>detecteing arrays all over the place,so those lines are well monitored!
>
>Smiles,
>Joe Robertson
"Men wanted for hazardous journey, small wages, bitter cold,
long months of complete darkness, constant danger, safe return
doubtful. Honour and recognition in case of success."
----- Sir Ernest Shackleton
=========================================================================
From: Chris and Susan Beck <n9zes@execpc.com>
Subject: Re: [JN] about the cathode interface
Date: Fri, 31 Mar 2000 16:10:24 -0600
Source: Sound Digest Archive v02.n506
Thanks for the interesting info. That's just what I was looking for. FWIW,
I've now got the scope calibrated (as much as I can do with the gear I have)
and really, all it needed was a tweak of the power supply -150V and the gain
on the CA plugin. The time bases look good, the triggering circuits were
really close, and everthing I put into the front end looks just amazing on
the CRT. I'm sure it's not up to absolute spec, but for what I am doing (Pk
to Pk measurements and general waveform analysis, it will work great.
Thanks!
Chris
longrie@mmace.nrl.navy.mil wrote:
> Hi Chris,
>
> Very interesting subject. The cathode interface was a very
> big deal to the tube manufacturers during the twilight of
> their era. Just how important was firmly established by
> Bell Labs in their early 60's R&D for their undersea sytems.
> These undersea transoceanic cables had built-in repeaters
> with vacuum tube amplifiers. Servicing these tubes would not
> be an option. They had to work for a design life measured in
> decades.
> So, through their investigations, Bell Labs became quite
> knowledgeable on tube reliability factors. Turns out that there
> are two main mechanisms of normal aging in an oxide cathode tube.
> There are plenty of other failure mechanisms, but just two *normal*
> aging processes.
> One is barium depletion from the oxide. Barium has a ready
> supply of low-work-function free electrons. When the barium
> content dwindles in the oxide, the work function shoots up higher,
> and it becomes much harder for electrons to escape the cathode.
> The low work function property of barium that makes it valuable
> as an emitter also makes it chemically active. It tends to
> react with impurities and stay bound up that way. It can vaporize
> and plate out upon the tube structures.
> Two is the growth of this cathode interface. This is the
> interface layer between the snowy white oxide and the (normally)
> nickel sleeve. Over the life of the tube, a slow chemical
> reaction takes place here wherein the trace impurities in both
> the oxide and the nickel combine to form this resistive interface.
> A new tube already has an interface resistance of 10 ohms or so.
> Over the tube lifetime, in a normal production tube, this resistance
> grows to numbers like 500 or 1000 ohms. Much worse in special cases.
> 500 or 1000 ohms internally in a tube seriously disrupts the
> transconductance, limiting the emissions. There are other effects.
> There grows a rectifying effect across this interface. And there
> grows a capacitance in series with the plate to cathode path.
> It is interesting that Bell Labs identified and studied these
> phenomena by using their recently developed semiconductor techniques.
> After all, they had invented the transistor just 12 or so years
> earlier and that kind of diagnostic thinking made the tube cathode
> interface study possible.
> Wouldn't you just know it though. The oxide cathode in a tube
> can be thought of as a kind of bulk semiconductor. And it is this
> semiconductor that fails in the tube.
> As for those AT&T undersea tubes, they are *still* working,
> some 40 years or 300,000+ hours later!
> So, to relate all of this to Tektronix scopes. If the tubes in
> a scope start drifting and changing their properties, then those
> scopes start drifting out of calibration. This effect happens to
> all tube equipment, not just Tektronix. But I take exception to
> a couple of the comments attributed to Stan Griffiths book. There
> isn't any way to directly check on the cathode interface. You
> check your tube for emissions. When emissions slowly decline, you
> know the cathode interface is building up. Nothing you can do
> about it. As to his comment about this occuring primarily in cut off
> tubes, does he really mean to imply that tubes left running won't
> age and grow weaker? This is simply not so.
>
> regards
>
> gary
>
=========================================================================
From: Kurt Steffensen <kurt-steffensen@teliamail.dk>
Subject: Re: [JN] about the cathode interface
Date: Sat, 01 Apr 2000 00:41:46 +0300
Source: Sound Digest Archive v02.n506
Highly interesting post , Gary.
I just wonder if I am getting this right.
That cathode interface thing , is that when the tube has been in a "sleep" mode
for a very long time , and it refuses to increase the
current ?
Kind of locked emission situation....
I have learned about this from personnel in the broadcasting , rec. studio and
military here in Europe.
Over here it is ( was ;-) considered the following way,.
A tube operated in steady continuos idle current service , or left with the
filament activated , for a very long time , were potential to develop a
"disease" in which they refused to alter the current.
These tubes could however from time to time , be restored to normal function , by
gradually forcing the tube to pass high pulses.
In other cases a new burn in was the cure. This was done by exceeding the
filament rating by say 10-20 % , for a limited time.
It might also be necessary to expose the tube to higher plate dissipation , than
the one rated.
This is very much similar to the threat that high quality tubes were exposed to ,
in the good old days , before they left the factory.
Another funny phenomenon similar to this was also known.
A tube that were used to pass ever changing signals , also for a very long time ,
would develop a condition , in which it had difficulties in return to a steady
idle current
situation.
In other words , it continued to operate "nervously" , though it were in a class
A mode.
If there were any potential cure for this , I can't remember , but I suspect long
expose to steady operating would improve the performance.
Though , tubes suffering from any of these "decease's" could be regarded as
bad/defective , they could easy pass a tube tester.
In Europe ( And also in at least one US-book , I know of ) , tube tester , no
matter how clever they were carried out , were never considered really
reliable.
The only 100% test , were an actual real life test.
It was also considered good practice in many important circuits , to leave the
tubes , with in their socket as long as possible.
Testing by actually removing the tubes , and imply them in a tube tester , and
back again , were considered more damaging to the performance , than
a test measured within the socket , by its "natural" circuit set up
characteristics.
The conclusion could be , to stress the tubes a little as ever possible.
The first two examples , will never occur in a normal domestic system.
But a dedicated DIY , might change/tweak his circuits in use , so much , that he
will actually never experience the best performance of the circuit.
If we ignore catastrophic failures , such as shorts , loose connections etc. , a
tube amplifier will normally show any errors , implied by the designer within
the first 200 to 3000 Hours.
Less radical designs errors will show up within approximately a year , of
continuos use.
If the design survives more than a year , it is very likely to be a good design ,
in the life time regards.
Another thing that can be observed within the circuits we play with , for
domestic use , is the "burn in"....
This is specially evident for pre-amplifiers and regulated tube PSU's.
If these are carefully designed , they will actually improve the noise
performance by 3-6 dB within a year in steady use.
After this they will stay here ( from time to time - even increase the
performance ) for several years.
If you have a good tube regulated supply , it is actually possible to observe the
improvement for the first week to 12 weeks.
In some cases , due to the ageing of the Voltage reference , it might even
improve the noise figures as much as 12 dB.
DC regulation , will also improve in many cases within the first few 100 hours.
The scout saying , that might be learned from this , could very well be " Leave
them tubes in peace...." ;-)
And regulate them Voltage , folks.
Maybe , you , Steve B. , have observed this during the time you wrote your
splendid article series about regulators ?
>
>
> Question: Bell Labs found that two factors contributed towards
> long lifetimes of tubes. One is to operate at reduced temperature.
Yes.This seems to be the case every time.
Good ventilation and/or reduced dissipation being the cases.,
However , by supplying the tube with reduced heater Voltage , this is not always
the case. On some tubes it is in fact the opposite condition , that gains tube
life.
And yet again , some tubes even by the same manufacture , behaved different in
this regard.
( According to mill. studies and other sources )
It was never covered , what actually influenced these phenomenon's.
> Isn't this one of Newton's Laws? Things go bad under temperature
> and pressure? The other thing was to use ultra, ultra, *ultra*
> pure materials in the nickel and oxide cathode construction.
> No impurities, no cathode interface.
Yes , I agree.
But one thing that is often considered as a tube defect , is the presence of
gasses.
Again according to mill. journals , no final conclusion was possible to this
condition.
Some tubes actually improved their performance , though gasses were released
inside the tube , and yet others behaved poor , despite extreme low
gasses in the envelope.
The usual tests for gasses inside the tube , as performed on a tube tester , are
actually not very reliable either.
The causes for this , were never really uncovered either.
This might be a surprise to many..?
> Sooo, what does this suggest to us about the 5751, 5814 and 6005?
At least I have on many , many occasion found that old 12AX7/ECC 83 , worked at
low current , say in a guitar amplifier , tested as new ,
despite of maybe 30 years of use....
> Question: I am wondering what the physical electronic mechanism
> might be that would account for cut off tubes ageing more
> rapidly. Maybe there is an obvious reason. I speculate that
> tubes run in cutoff have higher cathode temperatures. The same
> tube with a plate current has the benefit of lower cathode
> temperature by electron cooling. Assume the same heater voltage
> for each case. What do you think about that?
I have no clue... Hmm , what do you actually refer to by ageing ?
But I remember reading an explanation regarding this matter in a book , at some
time.
Something to do with a growth/build up of a more uniform layer , I belive.
I will look for it if you wish.
- - Kurt
=========================================================================
From: SBench@aol.com
Subject: Re: [JN] about the cathode interface
Date: Fri, 31 Mar 2000 20:43:01 EST
Source: Sound Digest Archive v02.n507
In a message dated 00-03-31 18:51:41 EST, kurt-steffensen@teliamail.dk writes:
<<
If you have a good tube regulated supply , it is actually possible to
observe the
improvement for the first week to 12 weeks.
In some cases , due to the ageing of the Voltage reference , it might even
improve the noise figures as much as 12 dB.
DC regulation , will also improve in many cases within the first few 100
hours.
The scout saying , that might be learned from this , could very well be "
Leave
them tubes in peace...." ;-)
And regulate them Voltage , folks.
Maybe , you , Steve B. , have observed this during the time you wrote your
splendid article series about regulators ?
>>
VR tubes do indeed stabilize with age. I'm not sure of the mechanism,
but it's probably related to the "impurities" associated with the rare gas.
Terman has a few note about this in the Radio Engineers Handbook
as well.
Actually, didn't notice much change during the regulator series checkout,
but that's because I routinely "burn in" the VR tubes as soon as I acquire
them. The only counter-example to this is 0G3s. AES had a sale on 'em
a while back, but I've not gotten around to burning them in due to that
dxxn inconvenient loctal socket ;-)
Best Regards,
Steve
=========================================================================
From: Kurt Steffensen <kurt-steffensen@teliamail.dk>
Subject: Re: [JN] about the cathode interface
Date: Fri, 31 Mar 2000 23:17:48 +0300
Source: Sound Digest Archive v02.n507
SBench@aol.com wrote:
> Interestingly enough, some of those connections are more desireable
> than satellite connection. Reason: Echo. The delay via a bird is
> higher than thru the cable, making more exotic use of echo cancellers.
> For data traffic, OTOH, not an issue.
Hmm.. Funny...
I wasn't aware of that.
I have often , speculated though , would it not actually be a better idea , to
kind of swap the "surface" signals with the air signals.
I mean , radio , TV etc. , ought to be in cables , and communication and data
transmission were better served by air ?
Ofcourse it would probably harder to control the money flow.
Those that owns the data cables , will be dealing with multi Giga bucks in the
near future.
I guess soon it will be hard to decide if we need/wish to pay per Bit or per the
minute...
- - Kurt
=========================================================================
From: Douglas Purl <dcp@selway.umt.edu>
Subject: Re: [JN] about wavelengt amp and lowther speaker
Date: Sun, 30 Jan 2000 03:19:35 -0700 (MST)
Source: Sound Digest Archive v02.n425
> sirs------------
>
> last week I ask if anyone on Joenet knows why these Wavelenght amps and
> Lowther speakers do not sound so good. But now I am seeing the maker of
> Wavelength, accuses me of being some other person, trying to attack him!
>
> Why is this happening??? I do not wish to harm
> anyone, I simply want to ask others of their
> past knowledge of these amp and speakers. I and friends
> are not impressed with them in our opinions. That is all I say.
Are we interested in your opinions or in those of your unidentified
friends, your mother and sister. The maker of Wavelength offered to
examine your non-existent amp for free and correct any malfunction.
Did you respond to him?
Perhaps if mommy increases your allowance you can save for a Wavelength.
By the time you get your driver's license you may own one.
Doug Purl
=========================================================================
From: DavidObxlover@aol.com
Subject: [JN] about wavelengt amp and lowther speaker
Date: Sun, 30 Jan 2000 04:39:02 EST
Source: Sound Digest Archive v02.n425
sirs------------
last week I ask if anyone on Joenet knows why these Wavelenght amps and
Lowther speakers do not sound so good. But now I am seeing the maker of
Wavelength, accuses me of being some other person, trying to attack him!
Why is this happening??? I do not wish to harm
anyone, I simply want to ask others of their
past knowledge of these amp and speakers. I and friends
are not impressed with them in our opinions. That is all I say.
Thank you..
=========================================================================
From: Kurt Steffensen <kurt-steffensen@teliamail.dk>
Subject: Re: [JN] about wavelengt amp and lowther speaker
Date: Sun, 30 Jan 2000 16:16:59 +0300
Source: Sound Digest Archive v02.n425
DavidObxlover@aol.com wrote:
> sirs------------
>
> last week I ask if anyone on Joenet knows why these Wavelenght amps and
> Lowther speakers do not sound so good. But now I am seeing the maker of
> Wavelength, accuses me of being some other person, trying to attack him!
Dear David.
I am sorry for you , and feel with you , as the situation has developed
such.
But please , consider the fact...
When I first saw your post , I was puzzled by the way you asked..
You did not gave any details , data , description or any other hint , that
could help us with a sensible reply.
I wondered about this , and felt the message had another value than the one
written.
Now , mind you , that I live in Denmark , and knows absolutely NOTHING at
all about those wavelength amplifiers ,
I did not even knew , that it was a Joe , that was responsible for these.
I know Gordon well , - But I did not connect these two.
I only know Gordon from a very good side , - and still do.
( I am sure , that Gordon will send me a few schematics or pix of the
amplifiers , when he reads this ;-)
Now , I replied to you and asked for a little more details in order to
understand the problem.
But you never even took the time to reply to me...?
So you have to admit , that all signs in moon and star , seems to indicate
that indeed there was another hidden purpose
of your message.....
Never mind that , I trust you , and believe it is all a unfortunate mistake.
That is very easy for you to settle , all you need to do , is to jump at
Gordons kind offer , and
send the amplifier to him , and the matter is out of the world.
He will then be able to track the problems with the amplifier , and fix it.
(And you got yourself a damn cheep valve amplifier :-)
Now , we are at it , please let us know who you are and where you live.
That will also prove your good intentions.
Good luck with it.
- - Kurt
=========================================================================
From: Steve Van Osdell <svanos@queencity.com>
Subject: [JN] About WE247A tubes
Date: Sat, 12 Aug 2000 18:32:28 -0400
Source: Sound Digest Archive v02.n625
I recently posted a short message here regarding a couple of WE247A
tubes that I had on ebay (in case anyone was interested in them). I
had no idea of what they were worth except for one person's (who is very
knowledgeable in this hobby in general) opinion which was 'they ought to
be worth at least about $70 each'.
So, it seems to me that if this estimate is wrong, someone would kindly
point it out to me in a helpful and friendly way rather than through a
negatively worded innuendo.
Just today I am passing on some WE tubes to a few Joes at super good
prices because they are in need of them. I am not trying to get top
dollar from any 'Joe' for me tubes - it is just that some of them I
really don't know what they are worth.
Thanks, Steve
=========================================================================
From: dslagle@earthlink.net (dave slagle)
Subject: Re: [JN] About WE247A tubes
Date: Sat, 12 Aug 2000 22:31:36 -0400
Source: Sound Digest Archive v02.n625
put them up on ebay with no reserve... and a $1 starting bid.. you will see
what they are worth.
hell i've seen 437A's go for less that $130 a pair... and they are a real
tube...
dave
=========================================================================
From: tube@jump.net
Subject: Re: [JN] About WE247A tubes
Date: Sun, 13 Aug 2000 09:36:04 -0500
Source: Sound Digest Archive v02.n626
Steve,
I think it's great that you are offering these tubes at low prices, and I
assure
you that no one wants to slam you personally. However, this is a VERY
irreverent buch here, and if the opportunity to make a good joke appears,
it is almost a certainty that someone will take that opportunity.
I try to take the attitude, "Okay assholes, you've had your fun, now answer
my damn question!"
I am puzzled the whole 12AX7 thing, however. My books say that the 247A
is a higher mu version of the 244A, which in turn is a high quality 227
(type 27).
The 244A has a mu of 10, while the 247A has a mu of 15. The ones in my
pictures also have a "mesh plate", like the old 27's, which is currently
much in
vogue (I don't know if it's just correlation or actually causation, but
mesh-plate
tubes usually sound better). No idea of their current worth, alas.
Phil
Steve Van Osdell wrote:
> I recently posted a short message here regarding a couple of WE247A
> tubes that I had on ebay (in case anyone was interested in them). I
> had no idea of what they were worth except for one person's (who is very
> knowledgeable in this hobby in general) opinion which was 'they ought to
> be worth at least about $70 each'.
>
> So, it seems to me that if this estimate is wrong, someone would kindly
> point it out to me in a helpful and friendly way rather than through a
> negatively worded innuendo.
>
> Just today I am passing on some WE tubes to a few Joes at super good
> prices because they are in need of them. I am not trying to get top
> dollar from any 'Joe' for me tubes - it is just that some of them I
> really don't know what they are worth.
>
> Thanks, Steve
=========================================================================
From: "Jan Hass" <jh@hifi-analyse.dk>
Subject: [JN] A brandnew Joe - Triode Festival.
Date: Sun, 12 Aug 2001 18:29:32 +0200
Source: Sound Digest Archive v02.n944
Hi Triode Festivallers
Greatings from Kim and I.
A few minutes ago I had Kim on the phone. He´s girlfriend just gave birth to
a helthy little Joe. Congratulations !! If you wish to send greatings here
is Kim´s e-mail address: kim@baysmidt.com
What would a very little new Joe want for birthpresent ? Any ideas ?
Thanks for all the pictures - Kim took also many pictures, they will be
published on my website when Kim can spare some time !?
Great seing y´all again this year. Had a lot of fun again. Great thanks to
Kurt, Karen and all their friends and family.
Received much usefull comments on our new Coax loudspeaker. The Coax
loudspeakers vere a little premature for this event since cross-overs aand
overall voicing vere not finished. They still are not, but already
preforming much better.
Best wishes
Jan Hass
mailto:info@hifi-analyse.dk
=========================================================================
From: longrie@mmace.nrl.navy.mil
Subject: A Brief History of Thermionics, was Re: [JN] 7868 replacement?
Date: Thu, 30 Nov 2000 15:41:58 +0000
Source: Sound Digest Archive v02.n749
[several pages snipped}
Thanks JC! That was great.
gary
"Those who fail to remember history are ... um
=========================================================================
From: Zyxtan@aol.com
Subject: Re: [JN] Absolute phase
Date: Wed, 24 Feb 1999 12:36:38 EST
Source: Sound Digest Archive v02.n059
In a message dated 2/24/99 12:15:47 PM US Eastern Standard Time,
Torsten.Loesch@enhar-ha.nthames.nhs.uk writes:
> > How important is absolute phase?
>
> According to some - extremely.
>
> According to me...?
>
I have hooked a function generator to the input of my preamp and then scoped
to verify the output from the power amp is truly in phase with the
input(within reason) .It was. The thing you cannot control is the media, how
would you know the recording engineer has his equipment in phase-you have no
control over that unless you are that engineer. An interesting test that Simon
can perform is a self recorded message in Cool Edit, this program is free and
easily downloaded. It allows the user the option of inverting the recorded
signal-and comparing the sound fairly rapidly.Let yourself be the judge, some
recorded sounds seem to be sensitive to this inversion others do not. The old
Sex Pistols records do not seem to sound any different whether the signal is
inverted or not......
paul(zyxtan@aol.com)
=========================================================================
From: Roscoe Primrose <roscoe@aiko.com>
Subject: Re: [JN] Absolute phase
Date: Wed, 24 Feb 1999 13:10:56 -0500
Source: Sound Digest Archive v02.n059
Simon Busbridge wrote:
>
> Folks,
>
> How important is absolute phase? Split riaa phono stages generally
> invert, but is this audible? What is the physiology of the ear's
> response to a reversed phase signal, and can it be heard?
>
> Are they any neat ways of correcting the phase - I can think of using a
> transformer but it is expensive.
>
Try reversing the connections either to your cartridge or speakers. Of
course, do you know whether your pre-amp or power amp inverts phase?
Not to mention that half your albums are probably out of phase with the
other half... (same thing with your CDs)
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] Absolute phase
Date: Wed, 24 Feb 1999 13:30:58 -0500
Source: Sound Digest Archive v02.n059
hi simon,
i have found that absolute phase is important (using the term loosely).
interestingly enough, i find that i prefer the sound of my amps
in an "inverting" configuration.
i simply connect my speaker wires black-to-red and red-to-black.
at first i though that i was picking up a phase inversion further up-stream
(in the preamp, for example) so the speaker swap was actually correcting for
it.
and lo-and-behold, i was inverting in the preamp (common cathode into a
white-follower).
so i pulled out the preamp and ran the CD directly into the amp.
guess what? no difference.
also preformed this type of experiment at dave slagle's.
we swapped phase at the output of his DAC. no change.
but swap speaker leads - big change.
i recently sold a copy of my "darling" amp to a guy via the internet.
i told him to do the speaker swap thing and report back.
i did not tell him what to expect (in fact, i told him that there might not
be any diff. at all)
his finding and preference was the same as mine:
1. the inverted configuration had more apparent bass
(sorta contradicts johannes chiu's theory regarding the 2nd harmonic
distortion of the output stage -and that the positive portion of the
waveform
should PUSH the speaker)
2. the image was wider, with more separation of instruments, and also
higher above the speakers in the inverted config.
3. just plain sounded better this way, so hang the red and black...
(i use monocolor binding posts on all of my amps now -
hook it up by ear.... ;) )
4. swapping phase earlier in the signal stream did not seem to
have much of an effect ...
i plan to demo this phenomena at nynoise
along with my "IMAGE" switch .... ;)
can't wait!
bob.d.
> ----------
> From: Simon Busbridge[SMTP:S.C.Busbridge@bton.ac.uk]
> Sent: Wednesday, February 24, 1999 10:45 AM
> To: sound@io.com
> Subject: [JN] Absolute phase
>
> Folks,
>
> How important is absolute phase? Split riaa phono stages generally
> invert, but is this audible? What is the physiology of the ear's
> response to a reversed phase signal, and can it be heard?
>
> Are they any neat ways of correcting the phase - I can think of using a
> transformer but it is expensive.
>
> TIA
>
> Simon
>
> Simon Busbridge, BSc(Hons) PhD CPhys MInstP
> School of Engineering
> University of Brighton
> Lewes Road
> Moulsecoomb
> Brighton BN2 4GJ
> UNITED KINGDOM
>
> Tel: 0044 (0)1273 642542
> Fax: 0044 (0)1273 642327/642301
> e-mail: s.c.busbridge@bton.ac.uk, scbusbridge@hotmail.com
>
>
=========================================================================
From: Simon Busbridge <S.C.Busbridge@bton.ac.uk>
Subject: [JN] Absolute phase
Date: Wed, 24 Feb 1999 15:45:30 +0000 (BST)
Source: Sound Digest Archive v02.n059
Folks,
How important is absolute phase? Split riaa phono stages generally
invert, but is this audible? What is the physiology of the ear's
response to a reversed phase signal, and can it be heard?
Are they any neat ways of correcting the phase - I can think of using a
transformer but it is expensive.
TIA
Simon
Simon Busbridge, BSc(Hons) PhD CPhys MInstP
School of Engineering
University of Brighton
Lewes Road
Moulsecoomb
Brighton BN2 4GJ
UNITED KINGDOM
Tel: 0044 (0)1273 642542
Fax: 0044 (0)1273 642327/642301
e-mail: s.c.busbridge@bton.ac.uk, scbusbridge@hotmail.com
=========================================================================
From: Torsten.Loesch@enhar-ha.nthames.nhs.uk
Subject: Re: [JN] Absolute phase
Date: 24 Feb 1999 16:44:28 +0000
Source: Sound Digest Archive v02.n059
Hi there,
> How important is absolute phase?
According to some - extremely.
According to me...?
Well, the UK Copy of Stereophile a few month back had the Stereophile Test-CD
on the cover.
This contains a test for absolute phase (a track within which the phase is
inverted). Listening I was apalled by the magnitude of change. Testing it
with a few "goldeneared" friends we agreed the time of the cut between a few
of us to be exactly the same.
Concidering that my system does not feature any form of simple
Phase-Adjustment possibility (all single ended circuitry - only one
Transformer on the Output of the power-amp) I decided to immediatly forget
this experience and maintain my belief (despite evidence to the contrary)
that Absolute Phase Absolutely Doesn't Matter.
So far this approach has been succesfull. But my next Preamp project does
include an Output transformer and yes - it will have a Phase-Switch....
Later Thorsten
=========================================================================
From: davidbarnett@aristotle.net (David Barnett)
Subject: Re: [JN] Absolute phase
Date: Wed, 24 Feb 1999 18:40:36 GMT
Source: Sound Digest Archive v02.n059
On Wed, 24 Feb 1999 15:45:30 +0000 (BST), Simon Busbridge
<S.C.Busbridge@bton.ac.uk> wrote:
>Are they any neat ways of correcting the phase - I can think of using a
>transformer but it is expensive.
Unless you're using a Decca cartridge, you can just reverse the leads
connecting to the phono cartridge.
- --dnb
=========================================================================
From: "Bert Doppenberg" <lowther@wxs.nl>
Subject: Re: [JN] Absolute phase
Date: Wed, 24 Feb 1999 19:37:15 +0100
Source: Sound Digest Archive v02.n059
Hi all,
>How important is absolute phase? Split riaa phono stages generally
>invert, but is this audible? What is the physiology of the ear's
>response to a reversed phase signal, and can it be heard?
>
>Are they any neat ways of correcting the phase - I can think of using a
>transformer but it is expensive.
Not only the absolute phase of the signal is important (problem is that recordings aren't
all in the right phase!) but the electrical phase is even more important. Equipment could
be plugged into a electric point in two way's. Measuring the voltage between the ground of
the socket and the plugged in device will read more or less voltage. If one does this with
every device (choose the way with the lowest voltage) it could improve the quality of the
sound a lot! The measured device should not be connected to other devices with
interconnects though!
The absolut signal phase is very audible for musicians, or well trained ears. Abolute
electrical phase is very audible for everyone!
Bert
- ------
BD-Design -- Ontwikkeling en Distributie van geluidssytemen
E-mail: bd-design@vt52.com http://www.vt52.com/bd-design
Tel./Fax: (0341) 254500 Mobiel: (06) 51242990
Bert Doppenberg - Lowther Club Holland
E-mail: lowther@wxs.nl http://home.wxs.nl/~lowther/home.htm
=========================================================================
From: "Bert Doppenberg" <lowther@wxs.nl>
Subject: Re: [JN] Absolute phase
Date: Wed, 24 Feb 1999 19:42:20 +0100
Source: Sound Digest Archive v02.n059
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M````````````````````````````````````````````````````````````
M````````````````````````````````````````````````````````````
M````````````````````````````````````````````````````````````
M````````````````````````````````````````````````````````````
M````````````````````````````````````````````````````````````
M````````````````````````````````````````````````````````````
M````````````````````````````````````````````````````````````
M````````````````````````````````````````````````````````````
*````````````````
`
end
=========================================================================
From: "David B. Klein" <dklein@microtec.net>
Subject: Re: [JN] Absolute phase
Date: Wed, 24 Feb 1999 14:33:23
Source: Sound Digest Archive v02.n060
A 12:36 PM 2/24/99 EST, Zyxtan@aol.com a écrit :
>In a message dated 2/24/99 12:15:47 PM US Eastern Standard Time,
>Torsten.Loesch@enhar-ha.nthames.nhs.uk writes:
>The old
>Sex Pistols records do not seem to sound any different whether the signal is
>inverted or not......
Why, you tin-eared Philistine, you! We did some uncontrolled listening
tests, and 4 out of 5 thought that Johnny sounded more Rotten in
noninverting polarity, while 5 out of 5 noticed that Sid sounded more Vicious.
David
=========================================================================
From: Torsten.Loesch@enhar-ha.nthames.nhs.uk
Subject: Re(2): [JN] Absolute phase
Date: 24 Feb 1999 19:32:08 +0000
Source: Sound Digest Archive v02.n060
Hi there,
> The thing you cannot control is the media, how would you know the recording
> engineer has his equipment in phase
You got no clue. What is worse, I myself have done a few Multi-track
recordings with some Mic's in Phase - others out of Phase. What a mess.
Sounded okay though (was the only way it did actually).
I'm sure I'm not the only Engineer guilty of such practices.... Nowadays I
would no longer do this of course. Only now I do Computers and not music....
The result is that (to me at least) a easy Phase-Switch on the preamp is
desirable. Thus you can try Inverted/noninverted and let your ears decide.
And as it is a DIY Preamp, it's easy to X the switch if it does not do what
you want....
Ciao Thorsten
=========================================================================
From: "Bert Doppenberg" <lowther@wxs.nl>
Subject: [JN] Absolute phase
Date: Wed, 24 Feb 1999 20:01:44 +0100
Source: Sound Digest Archive v02.n060
Hi all,
>How important is absolute phase? Split riaa phono stages generally
>invert, but is this audible? What is the physiology of the ear's
>response to a reversed phase signal, and can it be heard?
>
>Are they any neat ways of correcting the phase - I can think of using a
>transformer but it is expensive.
Not only the absolute phase of the signal is important (problem is that recordings aren't
all in the right phase!) but the electrical phase is even more important. Equipment could
be plugged into a electric point in two way's. Measuring the voltage between the ground of
the socket and the plugged in device will read more or less voltage. If one does this with
every device (choose the way with the lowest voltage) it could improve the quality of the
sound a lot! The measured device should not be connected to other devices with
interconnects though!
The absolut signal phase is very audible for musicians, or well trained ears. Abolute
electrical phase is very audible for everyone!
Bert
- ------
BD-Design -- Ontwikkeling en Distributie van geluidssytemen
E-mail: bd-design@vt52.com http://www.vt52.com/bd-design
Tel./Fax: (0341) 254500 Mobiel: (06) 51242990
Bert Doppenberg - Lowther Club Holland
E-mail: lowther@wxs.nl http://home.wxs.nl/~lowther/home.htm
=========================================================================
From: evaguido <EvaGuido@iaehv.nl>
Subject: Re: [JN] Absolute phase
Date: Wed, 24 Feb 1999 20:25:19 +0100
Source: Sound Digest Archive v02.n060
Hi
To me differences in absolute phase can be heard, but are generally small,
compared to others aspects (buy a decent oscillator for your CD player:
that difference forgets you think on phase for a while.....)
More complicating is that e.g. in classical multi-mike recordings, violins
sound OK in one phase, and the copper sounds OK in the other
The phase difference was in the recording, between both (groups of)
micorophones....
Guido
At 15:45 24-2-99 +0000, Simon Busbridge wrote:
>Folks,
>
>How important is absolute phase? Split riaa phono stages generally
>invert, but is this audible? What is the physiology of the ear's
>response to a reversed phase signal, and can it be heard?
>
>Are they any neat ways of correcting the phase - I can think of using a
>transformer but it is expensive.
>
>TIA
>
>Simon
>
>Simon Busbridge, BSc(Hons) PhD CPhys MInstP
>School of Engineering
>University of Brighton
>Lewes Road
>Moulsecoomb
>Brighton BN2 4GJ
>UNITED KINGDOM
>
>Tel: 0044 (0)1273 642542
>Fax: 0044 (0)1273 642327/642301
>e-mail: s.c.busbridge@bton.ac.uk, scbusbridge@hotmail.com
>
>
>
=========================================================================
From: John Levreault <jlevro@mediaone.net>
Subject: Re: [JN] Absolute phase
Date: Wed, 24 Feb 1999 16:12:46 -0500
Source: Sound Digest Archive v02.n061
For more information than you'll ever want to know about absolute phase, see "The
Wood Effect" by the ever-erudite Clark Johnsen.
JL
=========================================================================
From: Torsten.Loesch@enhar-ha.nthames.nhs.uk
Subject: Re(2): [JN] Absolute phase
Date: 24 Feb 1999 21:07:15 +0000
Source: Sound Digest Archive v02.n061
Hi there,
> For more information than you'll ever want to know about absolute phase,
see
> "The Wood Effect" by the ever-erudite Clark Johnsen.
I shall read AFTER my system has gained the ability to switch the Absolue
Phase....
Great work for all I can say.... But do fit that Phase-Switch first....
Later Thorsten
=========================================================================
From: evaguido <EvaGuido@iaehv.nl>
Subject: Re: [JN] Absolute phase
Date: Wed, 24 Feb 1999 22:46:26 +0100
Source: Sound Digest Archive v02.n061
Hi
Most OUTPUT transformers, especially the SE ones, I heard untill know sound
different when the input phase is changed....
This is of utmost importanve if you change phase in front of them:
1-the sound may improve
2-the phase gets reversed so needs to be re-reversed
Guido
=========================================================================
From: evaguido <EvaGuido@iaehv.nl>
Subject: Re: [JN] Absolute phase
Date: Wed, 24 Feb 1999 22:46:30 +0100
Source: Sound Digest Archive v02.n061
Bert wrote:
>all in the right phase!) but the electrical phase is even more important.
>Equipment could
>be plugged into a electric point in two way's. Measuring the voltage
between >the ground of
>the socket and the plugged in device will read more or less voltage. If
one >does this with
>every device
This even holds for every secondary transformer winding
Guido
>(choose the way with the lowest voltage) it could improve the quality of the
>sound a lot! The measured device should not be connected to other devices
with
>interconnects though!
>
>The absolut signal phase is very audible for musicians, or well trained
ears. >Abolute
>electrical phase is very audible for everyone!
>
>Bert
>
>------
=========================================================================
From: davidbarnett@aristotle.net (David Barnett)
Subject: Re: [JN] Absolute phase
Date: Wed, 24 Feb 1999 23:56:15 GMT
Source: Sound Digest Archive v02.n061
On Wed, 24 Feb 1999 16:12:46 -0500, John Levreault
<jlevro@mediaone.net> wrote:
>For more information than you'll ever want to know about absolute phase, see "The
>Wood Effect" by the ever-erudite Clark Johnsen.
A short book, which would be even shorter of CJ didn't repeat
everything at least three times.
- --dnb
=========================================================================
From: Simon Busbridge <S.C.Busbridge@bton.ac.uk>
Subject: [JN] Absolute Phase
Date: Thu, 25 Feb 1999 11:25:09 +0000 (BST)
Source: Sound Digest Archive v02.n061
A big thank you to everyone how responded - it seems that it is important
and that there should be a switch because one does not know the phase of
the original recording.
Once concern about this - I recall that transformers should be connected
the "right way round" so that the signals ends are connected to the
windings nearest to the core and the outer ends "earthed". If the
secondary is swapped around will this not affect the frequency response?
Simon
Simon Busbridge, BSc(Hons) PhD CPhys MInstP
School of Engineering
University of Brighton
Lewes Road
Moulsecoomb
Brighton BN2 4GJ
UNITED KINGDOM
Tel: 0044 (0)1273 642542
Fax: 0044 (0)1273 642327/642301
e-mail: s.c.busbridge@bton.ac.uk, scbusbridge@hotmail.com
=========================================================================
From: "John Hancock" <John_Hancock@swissre.com>
Subject: [JN] Absolute Phase
Date: Fri, 26 Feb 1999 09:34:19 +0100
Source: Sound Digest Archive v02.n062
From: Torsten.Loesch@enhar-ha.nthames.nhs.uk
>I shall read AFTER my system has gained the ability to switch the Absolue
>Phase....
Why can't you just switch around your speaker wires?
From: Simon Busbridge <S.C.Busbridge@bton.ac.uk>
>If the secondary is swapped around will this not affect the frequency
response?
Doesn't the wiring of the primary matter only because of the DC component
of the voltage, not the AC. If there is distortion of the AC component,
you're going to get it regardless of which way you wire the thing, aren't
you? SInce there is no DC component on the secondary, why should it
matter?
=========================================================================
From: Torsten.Loesch@enhar-ha.nthames.nhs.uk
Subject: Re: [JN] Absolute Phase
Date: 26 Feb 1999 10:04:22 +0000
Source: Sound Digest Archive v02.n062
Hi there,
> From: Torsten.Loesch@enhar-ha.nthames.nhs.uk
> >I shall read AFTER my system has gained the ability to switch the Absolue
> >Phase....
>
> Why can't you just switch around your speaker wires?
I could. But to do so on each and every record and to try (possibly several
times) which polarity sounds better is too much work for me. Unless it's got
an easy to reach switch somewhere I leave well enough, well enough alone....
Later Thorsten
=========================================================================
From: John Levreault <jlevro@mediaone.net>
Subject: Re: [JN] Absolute Phase
Date: Fri, 26 Feb 1999 08:58:26 -0500
Source: Sound Digest Archive v02.n065
John Hancock wrote:
> From: Torsten.Loesch@enhar-ha.nthames.nhs.uk
> >I shall read AFTER my system has gained the ability to switch the Absolue
> >Phase....
>
> Why can't you just switch around your speaker wires?
No. The relative phase of the output tranny has a marked affect on the quality
of sound. Most manufacturers, well, MagneQuest anyway, have a recommended
primary connection that has something to do with voltage gradients across the
windings, which forces you to find the better phase with the output winding.
The technical reason for this relates to the phase of the second harmonic
relative to the fundamental and was discussed in a post by Johannes Chiu on
this list back on 6/21/94. I have a hardcopy. Perhaps someone has this saved
in an archive somewhere.
This assumes, of course, that correct system polarity is maintained by making
a polarity adjustment elsewhere in the system. I swap my phono cartridge
leads. Most DAC boxes have a phase switch, too. A linestage output tranny
would be a good place, too, as would an input tranny on the amp.
To make matters worse, Clark Johnsen claims that speaker drivers all have a
"better" polarity. It never ends.
JL
>
>
> From: Simon Busbridge <S.C.Busbridge@bton.ac.uk>
> >If the secondary is swapped around will this not affect the frequency
> response?
>
> Doesn't the wiring of the primary matter only because of the DC component
> of the voltage, not the AC. If there is distortion of the AC component,
> you're going to get it regardless of which way you wire the thing, aren't
> you? SInce there is no DC component on the secondary, why should it
> matter?
=========================================================================
From: Jeremy Epstein <jepstein@shwd.com>
Subject: [JN] Absolute Phase
Date: Wed, 18 Aug 1999 12:52:28 -0400
Source: Sound Digest Archive v02.n251
Question :
If I try this in my system, which has a powered subwoofer (which sadly
has no phase reversal switch) I will need to flip the line level signal
to the subwoofer in order to preserve relative phase with the subwoofer.
What's the best way to do this?
- -j
- --
=====================================
Jeremy Epstein .... jepstein@shwd.com
=====================================
=========================================================================
From: Thomas Danley <Tom@ppci.com>
Subject: Re: [JN] Absolute Phase, acoustic phase, the forgotten element.
Date: Fri, 26 Feb 1999 17:01:43 -0600
Source: Sound Digest Archive v02.n063
Torsten.Loesch@enhar-ha.nthames.nhs.uk wrote:
> Hi there,
>
> > From: Torsten.Loesch@enhar-ha.nthames.nhs.uk
> > >I shall read AFTER my system has gained the ability to switch the
Absolue
> > >Phase....
> >
> > Why can't you just switch around your speaker wires?
>
> I could. But to do so on each and every record and to try (possibly
several
> times) which polarity sounds better is too much work for me. Unless
it's got
> an easy to reach switch somewhere I leave well enough, well enough
alone....
>
> Later Thorsten
Doing it by ear is certinly the best way to judge polarity because even
a single
loudspeaker has an acoustic phase which will typically vary as much as
+ - 90
degrees (with respect to the input signal).and in multi way systems the
over all
acoustic phase shift is typically in hundreds of degrees.
The question of absolute phase becomes sort of a moot point when the
reproducer
does not preserve the phase of the signal driving it.
People usually describe the waveshape of a signal to argue that there is
absolute polarity, for example,
a firecracker going off but with reversed phase is a sound that can't
be
produced (a vaccuum implosion is close). Clearly some signals,
particularly if
asymetric do have absolute phase and I am sure some are audible..
On the other hand, for a speaker or any other device to reproduce a
complex
signal like the "N" wave of an explosion (or music) it must have flat
amplitude
response covering all the harmonics AND have zero degrees phase thru
that same
range. Zero degrees phase is NOT the same as "minimum phase" (the
latter
meaning that for any change in amplitude slope , there is a
corresponding change
in phase), Zero degrees phase means that the acoustic phase in the same
as the
input signal (or -180 of the polarity is reversed).
Also, this does not refer to the phase shift caused by the propagation
delay in
air, this is a "time delay"
added to the system and effects all frequencies equally. Test
instruments like
the TEF machine measure the amplitude and acoustic phase by first
measuring the
delay and offsetting the tracking reciever frequency
to only "hear" the direct (not reflected) sound.
Best Regards,
Tom Danley
ServoDrive inc
ITC
=========================================================================
From: Thomas Danley <Tom@ppci.com>
Subject: Re: [JN] Absolute Phase, acoustic phase, the forgotten element.
Date: Fri, 26 Feb 1999 08:43:49 -0600
Source: Sound Digest Archive v02.n066
Torsten.Loesch@enhar-ha.nthames.nhs.uk wrote:
> Hi there,
>
> > From: Torsten.Loesch@enhar-ha.nthames.nhs.uk
> > >I shall read AFTER my system has gained the ability to switch the Absolue
> > >Phase....
> >
> > Why can't you just switch around your speaker wires?
>
> I could. But to do so on each and every record and to try (possibly several
> times) which polarity sounds better is too much work for me. Unless it's got
> an easy to reach switch somewhere I leave well enough, well enough alone....
>
> Later Thorsten
Doing it by ear is certinly the best way to judge polarity because even a single
loudspeaker has an acoustic phase which will typically vary as much as + - 90
degrees (with respect to the input signal).and in multi way systems the over all
acoustic phase shift is typically in hundreds of degrees.
The question of absolute phase becomes sort of a moot point when the reproducer
does not preserve the phase of the signal driving it.
People usually describe the waveshape of a signal to argue that there is
absolute polarity, for example,
a firecracker going off but with reversed phase is a sound that can't be
produced (a vaccuum implosion is close). Clearly some signals, particularly if
asymetric do have absolute phase and I am sure some are audible..
On the other hand, for a speaker or any other device to reproduce a complex
signal like the "N" wave of an explosion (or music) it must have flat amplitude
response covering all the harmonics AND have zero degrees phase thru that same
range. Zero degrees phase is NOT the same as "minimum phase" (the latter
meaning that for any change in amplitude slope , there is a corresponding change
in phase), Zero degrees phase means that the acoustic phase in the same as the
input signal (or -180 of the polarity is reversed).
Also, this does not refer to the phase shift caused by the propagation delay in
air, this is a "time delay"
added to the system and effects all frequencies equally. Test instruments like
the TEF machine measure the amplitude and acoustic phase by first measuring the
delay and offsetting the tracking reciever frequency
to only "hear" the direct (not reflected) sound.
Best Regards,
Tom Danley
ServoDrive inc
ITC
=========================================================================
From: Scott Grammer <tubedude@sunnetusa.net>
Subject: Re: [JN] Absolute polarity
Date: Mon, 16 Aug 1999 20:34:17 -0400
Source: Sound Digest Archive v02.n248
Andrej Deticek wrote:(snip)
> Stu,(snip)
> It seems to me far easier to turn a switch, rather than changing the
> speaker wires..., especially if you want to change the absolute polarity
> frequently.
Andrej:
Don't you know that it is part of the True Audiophile Code of Ethics to
eschew convenience everywhere it rears it's ugly head?
:-)
S.G.
- --
"To save every cog and wheel is the first
precaution of intelligent tinkering." -Aldo Leopold.
What if there were no hypothetical questions?
=========================================================================
From: Andrej Deticek <andrej.deticek@siol.net>
Subject: Re: [JN] Absolute polarity
Date: Tue, 17 Aug 1999 00:43:13 +0200
Source: Sound Digest Archive v02.n248
"Anthony J. Knettel" wrote:
>snip
> On my CD's, 95% of them are recorded in reversed absolute polarity, although
> many are mixed up in polarity. At least with LP's it was maybe 60-40. Almost
> all my Columbia LP's are inverted. Check out the 2nd Chesky Test CD, it's
> inverted. Don't use the crappy switch as on the Adcom machines, flip your
> speaker wires around.
> Regards,
> Stu
>
Stu,
I wonder what would be the advantage of flipping the wires on the
speakers, rather than using a switch that changes the absolute polarity?
It seems to me far easier to turn a switch, rather than changing the
speaker wires..., especially if you want to change the absolute polarity
frequently.
Andrej Deticek
=========================================================================
From: John Levreault <jlevro@mediaone.net>
Subject: Re: [JN] Absolute polarity
Date: Tue, 17 Aug 1999 10:27:11 -0400
Source: Sound Digest Archive v02.n249
Andrej Deticek wrote:
> I wonder what would be the advantage of flipping the wires on the
> speakers, rather than using a switch that changes the absolute polarity?
> It seems to me far easier to turn a switch, rather than changing the
> speaker wires..., especially if you want to change the absolute polarity
> frequently.
Once again, I am reminded of Johannes Chiu's post to this forum of 21 June 1994
(has it been that long?) entitled "Importance of Phase Polarity in Single-ended
Amps", wherein he suggests that there is a single correct phasing of the output
transformer with respect to the output valve. He recommends that the polarity of
the speaker signal be the same as that at the grid of the output valve. This is
actually opposite what most output tranny manufacturers indicate with their wiring
phasing.
I for one agree with Johannes' recommendation, which offers an improved sense of
dynamics compared to the "other" connection. This assumes, of course, that proper
system polarity is maintained. In my case, I swap my cartridge connections,
although I suspect a DPDT on an output or input tranny would also work, Mr.
Wright's objections not withstanding.
JL
>
>
> Andrej Deticek
=========================================================================
From: "Danielak, Robert M" <robert.m.danielak@lmco.com>
Subject: RE: [JN] Absolute polarity
Date: Tue, 17 Aug 1999 12:13:34 -0400
Source: Sound Digest Archive v02.n249
i hope johannes is still with us.
if he's not too busy makin' plasma,
maybe he'll comment.... ;)
the term "absolute phase" was used here only to
differentiate between "relative-phase" between channels.
(e.g., speakers that are wired in opposite phase
sound hollow, weird imaging, makes your eyes cross...)
what johannes is talking about has nothing to
do with the way the music was recorded.
it is simply a way to "match" the characterisic
of the output stage to the speaker in the way that does
most good.
when the signal is amplified by the output tube
in an SE amp with no NFB, a significant amount of
2nd order distortion is created. to simplify
matters, assume a pure sine input to the grid of the
output tube (say it's a triode, like 2a3).
the waveform at the 2a3 plate looks pretty much
like the original sine wave, except the negative
portion of the sine is taller and skinnier-looking, while the
positive portion of the wave is shorter and fatter-looking.
if you placed a load line on the 2a3 characteristics
you will see that going from the nominal bias
(say -45V) up toward zero, the grid bias curves
are moving farther apart. therefore you traverse more
plate voltage, hence more negative voltage swing,
and a taller negative half-cycle.
going from -45 down to -90, however, the grid bias curves are bunching
closer together (down in that
nasty low current region). therefore you traverse less
plate voltage, hence less positive voltage swing,
and a shorter positive half-cycle.
for those of you folloing along with your RCA manual
use an abnormally low plate load (like <1k)
to emphasize the point.
ok, so johannes' idea is to use this over-emphasized negative
half cycle to *PUSH* the speaker cone forward.
if we assume that a positive voltage on the positive
speaker terminal moves the speaker diaphram outward
the output transformer must be designed to
invert the signal such that this negative plate
signal will be going to the speaker positive lead.
if we believe that transformers are built the way they are drawn in a
schematic (and assume that both "dots"
are on top) then the "start" of the primary winding
is connected to B+ = AC ground. the plate signal
is applied to the "finish" of the primary.
as drawn (since conventional "dots" are rarely shown)
one would assume that the "start" of the secondary
is on top, and is the amp "positive" output.
the secondary "finish" is the lower and is the amp's
"negative" output.
however, i don't believe this is the case with most output transformers. if
drawn correctly, the "dot"
would be at the top of the primary - connected to B+,
and at the bottom of the secondary - connected to
negative output = speaker negative....
in other words, i don't think most transformers are
designed to invert.
i could be wrong here. easy to mix one thing up and
flip the whole argument...
iirc, my two stage amps do not invert from input
to output. so you have one inversion in the 1st stage,
re- inversion in the output stage. so the transformer
cannot be inverting - otherwise the output would be
inverted from input....
additionally, i *always* prefer to have my speaker leads
*inverted*.
so i guess this corroberates johannes' theory.
the effect is definitely noticeable. especially on
amps with rather high 2nd harmonic distortion.
i've come to the point that, on amps that i build for
other people, i do not use the typical RED&BLACK
binding posts. i'll use all black, or green and yellow,
or white and green. i'll tell *them* to decide how
it sounds best.
annoys the f@#k out of some folks...
...until they try it.
i've kept a cheat-sheet, and so far, 100% preferred the
inverted configuration.....
fwiw: we also tried swapping phase at the source
(i.e., DAC or preamp ) output.
could not detect a difference in sound.... hmmm....
take care,
bob.d.
> ----------
> From: John Levreault[SMTP:jlevro@mediaone.net]
> Sent: Tuesday, August 17, 1999 10:27 AM
> To: Andrej Deticek
> Cc: Anthony J. Knettel; JoeList
> Subject: Re: [JN] Absolute polarity
>
> Andrej Deticek wrote:
>
> > I wonder what would be the advantage of flipping the wires on the
> > speakers, rather than using a switch that changes the absolute polarity?
> > It seems to me far easier to turn a switch, rather than changing the
> > speaker wires..., especially if you want to change the absolute polarity
> > frequently.
>
> Once again, I am reminded of Johannes Chiu's post to this forum of 21 June
> 1994
> (has it been that long?) entitled "Importance of Phase Polarity in
> Single-ended
> Amps", wherein he suggests that there is a single correct phasing of the
> output
> transformer with respect to the output valve. He recommends that the
> polarity of
> the speaker signal be the same as that at the grid of the output valve.
> This is
> actually opposite what most output tranny manufacturers indicate with
> their wiring
> phasing.
>
> I for one agree with Johannes' recommendation, which offers an improved
> sense of
> dynamics compared to the "other" connection. This assumes, of course, that
> proper
> system polarity is maintained. In my case, I swap my cartridge
> connections,
> although I suspect a DPDT on an output or input tranny would also work,
> Mr.
> Wright's objections not withstanding