Sound Practices Mailing List Files - Volume 1
=========================================================================
From: Joseph Lowe <jlowe@cdc.net>
Subject: Re: 805 in SE ?
Date: Wed, 18 Feb 1998 14:01:46 -0500 (EST)
Source: Sound Digest Archive v01.n196
On Wed, 18 Feb 1998, Petter Eneroth wrote:
> Hoping for a gain of ~40 from the E810F.
If you are using choke loading with a follower you will get gain=Mu which
is 56 for the E810F/7788 in triode connection. These tubes sound good, I
think you will like them. What are you going to use for bias on them? I
use a single C NiCad with around 150V on the plate.
>
> Feedback on 805's in SE use much appreciated.
I have used the 838 which is very similar, and I found that using the
secondary of the OPT in the cathode circuit gave about 6db feedback.
Of course you stated that your cathodes would be at +200V, that means your
speakers would be "hot" with this arrangement.
=========================================================================
From: Petter Eneroth <ehp@ffa.se>
Subject: 805 in SE ?
Date: Wed, 18 Feb 1998 17:35:31 +0100
Source: Sound Digest Archive v01.n196
I have started building a SE 805 amp. Plans are to use E810F Pentodes
as pseudo-triodes with SE xformers as plate chokes this stage will be
followed
by a mosfet "cathode follower" to drive the 805's which have large
bypassed
cathode resistors in order to raise the cathodes to (~200v) thus
avoiding
a coupling cap from the MOSFET stage. Preliminary operating point for
the 805:
load ~5k 600 volts 100mA +20v grid bias but this is just guesswork
really.
Hoping for a gain of ~40 from the E810F.
Feedback on 805's in SE use much appreciated.
Best regards Petter Eneroth.
=========================================================================
From: "JF" <jimfl@CyberRamp.net>
Subject: Re: 805 in SE ?
Date: Wed, 18 Feb 1998 19:23:31 -0600
Source: Sound Digest Archive v01.n196
Tungsten Joes,
Nobu Shishido has designed an 805 SE amplifier (WAVAC 805) that uses two
feedback paths. For a similar circuit, see page 7 of SP issue 10. For the
805, the OT primary is 3.5kohm, K-NFB winding is 36 ohm, and the operating
conditions are 800V plate, 135mA Ip at +27V on the grid. I believe he uses
special Tango trannies.
Mr. Shishido has written book on this style of amplifier. If it wasn't
written in Japanese, I'd buy it, even at the $60 price tag.
The 805 and the similar 838 triodes have a grid designed so that the
amplification of the tube varies with the amplitude of the signal. The
claim is made that this facilitates the design of class B amplifiers with
low distortion at high output. (This design feature is revealed in the
TT-3 manual but is absent from the TT-5 manual.) And yet, the book states
that if the distortion is to be kept below 3%, a different bias is
suggested other than the zero bias point. The nuance of this is lost on
me, and I'd search for an explanation, but the chosen operating point is so
different from the manual that I'm only vaguely interested in the answer.
I built an 805 prototype to experiment with different OT feedback
arrangements and class A2 driver circuits. The 805 worked great, but I
have since replaced it with an 810. This amp has been temporarily shelved
while I work on an 845 parafeed. I am very interested to hear what you 805
and 838 guys come up with.
JF
=========================================================================
From: AirGapped@aol.com
Subject: Re: Re: 805 in SE ?
Date: Thu, 19 Feb 1998 00:00:58 EST
Source: Sound Digest Archive v01.n196
In a message dated 2/18/98 8:52:24 PM, jimfl@CyberRamp.net wrote:
>
>
>I built an 805 prototype to experiment with different OT feedback
>
>arrangements and class A2 driver circuits. The 805 worked great, but I
>
>have since replaced it with an 810. This amp has been temporarily shelved
>
>while I work on an 845 parafeed. I am very interested to hear what you 805
>
>and 838 guys come up with.
>
Hey Jim: Sure would be interested in hearing what your doing with the 845
parafeed. Hope it's not a top secret project.
One other question...if anyone in Joeland can answer.....is there a set of
operating parameters for the 805 that does not go positive? I have two pairs
of these tubes (Amperex's if I recall) in my basement...they sure are good
lookers. What if I did not care one iota about output power level....is there
some way to tame these beasts (plate voltage and plate current wise) and get
them to boogey at all?
Mike
=========================================================================
From: "JF" <jimfl@CyberRamp.net>
Subject: Re: Re: 805 in SE ?
Date: Thu, 19 Feb 1998 07:18:57 -0600
Source: Sound Digest Archive v01.n196
> From: AirGapped@aol.com
>
> One other question...if anyone in Joeland can answer.....is there a set
of
> operating parameters for the 805 that does not go positive? I have two
pairs
> of these tubes (Amperex's if I recall) in my basement...they sure are
good
> lookers. What if I did not care one iota about output power level....is
there
> some way to tame these beasts (plate voltage and plate current wise) and
get
> them to boogey at all?
>
> Mike
I think you'll find it difficult to get much out of the 805 without driving
the grid positive. Also, the negative grid voltage area (near cuttoff) of
the plate characteristics is much more "bunched together" than one would
normally expect. This might be due to the variable mu grid design. At
800Vp and 0Vg, Ip is 40mA and -10Vg is nearly cutoff. At 1400Vp, -10Vg
will get about 40mA Ip.
This shouldn't be taken as discouragement, it only appears that it might be
challenging according to RCA. I've never tried to operate the 805 like
that and therefore have zero experience on how it will sound "down there".
Send me your fax number and I'll gladly shoot you a copy of the plate
curves. These curves can be found in RCA's TT-3 and Kloeffler's
"Industrial Electronics and Control" among other places.
JF
=========================================================================
From: Ted.Riesz@mailhost.dpie.gov.au
Subject: RE>805 in SE ?
Date: Thu, 19 Feb 1998 10:19:56 +1100
Source: Sound Digest Archive v01.n196
RE>805 in SE ? 2/19/98
I also am very interested in this topic and wish Petter well with his project.
I have a few old 805's but was initially put off by the likely cost of suitable output iron (eg spec
ialised Tangos). What type of OPTs are you proposing to use Petter?
Regards
Ted Riesz
- --------------------------------------
Date: 2/19/98 4:25 AM
To: Ted Riesz
From: ehp@ffa.se - SMTPGATE
I have started building a SE 805 amp. Plans are to use E810F Pentodes
as pseudo-triodes with SE xformers as plate chokes this stage will be
followed
by a mosfet "cathode follower" to drive the 805's which have large
bypassed
cathode resistors in order to raise the cathodes to (~200v) thus
avoiding
a coupling cap from the MOSFET stage. Preliminary operating point for
the 805:
load ~5k 600 volts 100mA +20v grid bias but this is just guesswork
really.
Hoping for a gain of ~40 from the E810F.
Feedback on 805's in SE use much appreciated.
Best regards Petter Eneroth.
=========================================================================
From: Petter Eneroth <ehp@ffa.se>
Subject: 805 in SE cont.
Date: Thu, 19 Feb 1998 14:13:54 +0100
Source: Sound Digest Archive v01.n196
This is a multi-part message in MIME format.
- --------------1268ED610C0CA27549C95A84
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Thanks to those who replied to my 805 post.
Actually I have gotten most of the ideas for this project
by following this group. Especially I would like to thank Joseph Lowe
who gave tips on using 7788 and 805 and J.-M. Le Cleac'h for using a
mosfet
follower.
I will start with trying 2 Nicads for bias and ~200 B+. 2 Nicd's in
order
to get input headroom was my thinking.
I will try to measure some distortion spectra on the driver
circuit.
( dont know if some salvaged (60's) measuring gear will work).
As Joseph Lowe pointed out the speakers would end up at +200
with feedback to the 805's cathode ( hadn't thought about that).
Starting without fb first.
OPT's will be Lundahl 1623 / 120 mA which can be connected either
for 5.6k or 3k impedance. I got the impression the 805 has a rather
large
Ri so perhaps 5.6k is best.
Thanks to JF for the SP reference with very helpful op poimts and his
impressions of the 805.
I attach a gif preliminary Schematic and hope to report some findings
in a week or so.
Petter Eneroth.
- --------------1268ED610C0CA27549C95A84
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- --------------1268ED610C0CA27549C95A84--
=========================================================================
From: Petter Eneroth <ehp@ffa.se>
Subject: 805 in SE, followup
Date: Tue, 07 Jul 1998 14:12:17 +0200
Source: Sound Digest Archive v01.n335
I built the SE 805 amp. Using E810F Pentodes
as pseudo-triodes with SE xformers as plate chokes (2.8v battery bias).
This stage
is dc coupled to a mosfet "cathode follower" to drive the 805's which
have
large
bypassed cathode resistors in order to raise the cathodes to (~200v)
thus
avoiding a coupling cap from the MOSFET stage. Outputs Lundahl 1623.
I glued a lot of things with epoxy which had worked on other
occasions but this glue must have gone bad. A lot of glued things fell
off.
I only got to listen to it for 20 minutes at low levels in the middle of
the night. I live in a small apartment with my girlfriend, the kitchen
had been
a construction site for 2 months and despite my promises of a small amp
i couldn't
help myself, the powersupply was in the 75kg range. My girlfriend will
get
a resting period from amp building. I havent done anything for 3 months.
So I still listen to my old amp, picture at
(http://www.angelfire.com/wy/eneroth/amp.html).
- --
Petter Eneroth mailto:ehp@ffa.se
Stockholm Sweden
=========================================================================
From: Petter Eneroth <ehp@ffa.se>
Subject: 805 in SE update.
Date: Wed, 04 Mar 1998 12:35:20 +0100
Source: Sound Digest Archive v01.n207
This is a multi-part message in MIME format.
- --------------1A4FC891D66F0A2EE7F287E1
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Building things take longer than expected as usual. I have some
things left on the powersupplies. I will use c-tapped AC heaters on the
805's using a Variac for slow start. There will be three separate B+
for each channel. All using IR 1200V 6A Hexfreds and L-C with
large elyts.
What kind of smaller caps are suitable to bypass with?
The supply for the 805 uses SOLA constant voltage xformers. These
provide something more similar to square waves. Peak value 960V
RMS 810 volts, a normal supply would have a peak of 1.4*810=1134V I
suppose. I read that they respond to voltage changes within 2-3 cycles.
Thus the regulating seems limited in bandwidth.
I will start with -1.5v bias and 150v on the E810F instead of -3 200v.
One thing I will try for fun is to drive some old Philips 800 Ohm
speakers
(not the bigger 9710, some smaller type) after the mosfet follower.
Attaching the gif schematic.
Best regards Petter Eneroth Sweden.
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- --------------1A4FC891D66F0A2EE7F287E1--
=========================================================================
From: Jeff Mai <jmai@fn.net>
Subject: Re: 805 multicells (Was: Bass reflex/Jensen/Onken)
Date: Sun, 8 Feb 1998 18:33:39 -0600
Source: Sound Digest Archive v01.n186
>I'm surprised anyone would want to use an 805 in the home. The one's I've
>heard were just relatively thin sheet metal spotwelded together and sounded
>like it. The custom built wood versions were very impressive though.
>
>GM
Hmmm... I think my 805s sound pretty awesome with 291-16K drivers and a
Hiraga style crossover. But then I haven't had a chance to compare them to
many other horns.
They are damped a little with some type of sputtered on material. Tapping
on them sounds more like plastic than metal. I would agree that they could
be better damped. I'll bet the early tar/pitch damped multicells would be
close to as dead as concrete (and nearly as heavy!)
Just my 0.02
Jeff
=========================================================================
From: "Mark Donen" <soledadd@worldnet.att.net>
Subject: 806A impedance peaks found
Date: Wed, 6 May 1998 17:30:12 -0400
Source: Sound Digest Archive v01.n271
For anyone interested:
I had a look at the impedance of my 806A driver (on the horn). The major in
band peak is at 1300Hz up to around 30/25 ohms. This peak spreads, while
diminishing slightly in size, to 1700Hz. The impedance also peaks out again
bigtime at 16K or so (as Lynn mentioned also), but it is acoustically very
rolled off way up there. There is also a smaller peak (16ohms) at 400 Hz. I
was not able to measure the freq response, but to the ear from repeatedly
sweeping, you can hear roll off from 3.5K which seems to continue on a
fairly steady decline until you get to 8K. From there to 14K things decline
faster and after 14K the thing seems to stop (might have been me ears!). On
the subjective side anything below 800Hz starts to sound a pretty horny or
suffering from megaphonitis ie the tone was not as clean and clear as above
this point. So 1000Hz (guestimated by Tom Danley) actually seems like a
pretty good crossover point.
I also had a short but informative conversation with a tech, Mike O'Neal,
at Altec. His recommendation for a crossover was quite different. He
suggested rollong off the woofer (if it is an Altec 15") lower than 500Hz
due to a peak in its upper response and suggested crossing the 511 horn
much higher at 2.5K or so using an underdamped second or crossover. The
values he gave over the phone were the following:
Tweeter: 1uF & .75 mH or 1.5uF & 1mH
Woofer: 25uF & 2.5 mH
This supposedly roughly compensates for peaks in both woofers and tweeters.
Later,
Mark
=========================================================================
From: "Mark Donen" <soledadd@worldnet.att.net>
Subject: 806A resonant frequency
Date: Thu, 16 Apr 1998 16:18:28 -0400
Source: Sound Digest Archive v01.n254
Hi,
Do any of the Altec or compression driver fans out there have a spec for
the resonant frequency of the 806A??
I don't know if this is important to know but I just put new 8ohm diaphrams
in which were marked for 902 drivers. The Altec part number is 34647.
Also does anyone know how to design a LCR network that will trap out this
peak?
Best,
Mark
=========================================================================
From: bill gardner <wg44929@navix.net>
Subject: Re: 806A resonant frequency
Date: Fri, 17 Apr 1998 08:42:15 -0500
Source: Sound Digest Archive v01.n254
At 04:18 PM 4/16/98 -0400, Mark Donen wrote:
>Hi,
>
>Do any of the Altec or compression driver fans out there have a spec for
>the resonant frequency of the 806A??
>
>Also does anyone know how to design a LCR network that will trap out this
>peak?
>
>Best,
>
>Mark
> Thanks Mark , In a coversation yesterday JC suggested I try this
same approach . I 'm messing with some 288 C c\drivers on 8 cell horns . I
sure could use some info regarding the resonant frequency of the 288s.
Thanks Bill Gardner
=========================================================================
From: "Ken Dangerfield" <bpyakd@mail.island.net>
Subject: 808
Date: Thu, 4 Dec 1997 21:04:22 -0800
Source: Sound Digest Archive v01.n125
After seeing Ed Billeci's amps at VSAC, and hearing the SV572-10 at
VSAC and several conversations with John Camille about the "sparkle"
of thoriated tungsten, I have to admit that my interest in tungsten
output tubes is more than a little piqued.
A tube collector I came across on the net has offered to sell me (at
a reasonable price) a pair of 808s. Ed has kindly given my some
advice about his impressions of this tube (thanks Ed) - does anyone
else have any experience with this tube in SE amps and, if so, which
setup and what are your listening impressions? TIA for any comments
and advice.
Regards,
Ken Dangerfield
=========================================================================
From: Grego Sanguinetti <grego@latticesemi.com>
Subject: Re: 808
Date: Mon, 8 Dec 1997 12:12:45 -0800 (PST)
Source: Sound Digest Archive v01.n129
On Thu, 4 Dec 1997, Ken Dangerfield wrote:
> A tube collector I came across on the net has offered to sell me (at
> a reasonable price) a pair of 808s. Ed has kindly given my some
> advice about his impressions of this tube (thanks Ed) - does anyone
> else have any experience with this tube in SE amps and, if so, which
> setup and what are your listening impressions? TIA for any comments
> and advice.
I have done some experimentation with the 808. It needs to be run
in A2 so be prepared to spend some serious money putting an amp
together. I ended up driving the 808 with a "booster" amp and
so I had ALOT of transformers.
They are very cool and fun, but impractical. I will eventually put
a real 808 amp together but for now, there are other, just as good
and much more practical amps to build.
As an alternative I would suggest the 845. The chinese ones are
great and can be had cheaply. It likes A1 and can be powered by
a modest 600v supply. It looks fabulous when fired up and will
heat your room in the winter.
- -grego
=========================================================================
From: Ned Carlson <ned@triodeel.com>
Subject: 811 & 845
Date: Sat, 13 Dec 1997 19:23:11
Source: Sound Digest Archive v01.n134
Russell DeAnna wrote:
>
> I picked up a pair of NOS RCA 812As on Wednesday. I looked
> in my RCA tube manual and found no charts on any of the
> transmitter tubes.
Same as 811, but less gain mu is 28 instead of 160.
Generally they are both biased at 30 to 50 ma, depending on
the voltage. 812 needs more negative voltage.
With the same plate voltage they put out the same power
as Class B Amp.
811, 812, 813, and 845 are all in the RCA TT-5 Transmitting Tube
Manual, available in reprint for $13.95.
RCA data sheets for 811 and 845 can be seen at
http://www.triodeel.com/tubedata.htm
Typical audio amplifiers using 811 and 813
can be seen at:
http://www.triodeel.com/dusty1.htm
See
Gotham PFB-150 (811's)
RCA MI-12246 (811's)
Altec 1570B (811's)
Altec 260A (813's)
Best Regards, Ned Triode Electronics,2225 W Roscoe St
Chicago, IL, 60618 USA ph 773-871-7459 fax 773-871-7938
"Worldwide Service, Neighborhood Prices" since 1985
Open 12:30 to 8 PM CT, (1830-0200 UTC) 12:30-5 Sat, Closed Wed & Sun
See our constantly evolving web site at http://www.triodeel.com
Text file catalogs: Send a request to our Catalog 'Bot at
catalog@triodeel.com
=========================================================================
From: Michel Paquette <paqm01@GEL.USherb.CA>
Subject: Re: 811A in audio
Date: Thu, 25 Sep 1997 18:04:41 -0400
Source: Sound Digest Archive v01.n043
I wouldn't design an amp around the 811. It has a very high mu and the
plate curves are not pretty; it was designed for positive grid bias.
Michel
>Hello,
>
>Does anyone here have any experience using the 811A in a class A audio
>application? Specs would be nice. I only have class B and C parameters, but
>these just won't do for my audio needs :)
>
>
>
>Jim de Kort
>jdekort@xs4all.nl
>
>-----------------------------------------------
> For DHT tube data and tubes
> for sale, check out the
> PhaetoN HomePage
> http://www.xs4all.nl/~jdekort/
>-----------------------------------------------
=========================================================================
From: John Levreault <jlevro@shore.net>
Subject: Re: 811A in audio
Date: Thu, 25 Sep 1997 19:33:32 -0400
Source: Sound Digest Archive v01.n043
At 10:06 PM 9/25/97 +0200, Jim de Kort wrote:
>Hello,
>
>Does anyone here have any experience using the 811A in a class A audio
>application? Specs would be nice. I only have class B and C parameters, but
>these just won't do for my audio needs :)
>
>
The 811A is the first tube highlighted in the Shishido's "Single Ended
Amplifiers with Transmitting Tubes". He has a design using an SRPP 12AU7
driving a trioded 6F6, in turn driving an IT to the 811A. He biases the
811A at 430V/100ma with approximately +26V on the grid via the secondary of
the IT. Grid current is about 14ma. The output tranny is the X-3.5S, and he
gets about 10W at 5% THD. His technique is similar to that used in the 801A
design in SP10.
I also think Joe Lowe (Joe, are you out there?) has done some stuff with
this tube.
John Levreault
=========================================================================
From: Jim de Kort <jdekort@xs4all.nl>
Subject: 811A in audio
Date: Thu, 25 Sep 1997 22:06:40 +0200
Source: Sound Digest Archive v01.n043
Hello,
Does anyone here have any experience using the 811A in a class A audio
application? Specs would be nice. I only have class B and C parameters, but
these just won't do for my audio needs :)
Jim de Kort
jdekort@xs4all.nl
- -----------------------------------------------
For DHT tube data and tubes
for sale, check out the
PhaetoN HomePage
http://www.xs4all.nl/~jdekort/
- -----------------------------------------------
=========================================================================
From: el34@juno.com
Subject: Re: 811A in audio
Date: Thu, 25 Sep 1997 23:23:26 -0400
Source: Sound Digest Archive v01.n044
On Thu, 25 Sep 1997 19:33:32 -0400 John Levreault <jlevro@shore.net>
writes:
>I also think Joe Lowe (Joe, are you out there?) has done some stuff with
this tube.
I'm here.
Although I am not using them now, I do like the sound of the 811 in SE.
Some things I found:
1. The 811 (not 811A) was the best sounding.
2. Run 'em hot 600V @100MA. just a little color showing.
3. A step-down IT is required. I was using 2.8:1, In true Class B RCA
recommended 6:1. The input impedance is funky and requires a driver
that can stay linear with a varying load. Miller effect is very much in
play, because of the high Mu, the speaker load gets refelected back
into the driver.
4. You can use local feedback by running the cathode current through the
secondary of the output transformer. This gives killer bass
because of the increased damping factor.
5. DC on the filaments is an absolute must.
6. I did not like using more than 2 stages. Adding a big driver stage
compressed the sound. I liked a 6DJ8 input/driver stage. You can't
get full power this way, but what you get is good.
7. Overall the sound of this setup was real warm and liquid. Not
particuarly accurate, but you could sit and listen to it for hours
without getting tired of it.
Is this going to be your first / main amp? If so I would recommend taking
a more traditional path. I think this style of amp is very hard to do
right.
=========================================================================
From: match@ee.utah.edu
Subject: Re: 811A in audio
Date: Fri, 26 Sep 1997 07:56:21 +0000
Source: Sound Digest Archive v01.n044
Michel wrote:
> I wouldn't design an amp around the 811.
I've used these, I think there are better choices for SE, SV-572's
come to mind, however they can be made to work better than the curves
would suggest. Save yourself some hair-pulling by using an IT
transformer, if you try this. The grid current will kill you
otherwise.
> It has a very high mu and the
> plate curves are not pretty; it was designed for positive grid bias.
>
Almost true. It was designed to run in class B with NO bias.
In order to run it in class A we need lots of positive bias, but the
tube was never intended to be used this way (IMHO). As an RF linear
amp they are kinda fun.
They also make a great AM modulator in class B push-pull. It shows
potential as a PP AB tube, but who needs 200 watts of PP DHT's?
=========================================================================
From: Torsten.Loesch@FinanceManager.Finance.FinanceAndInformation.enhar-ha.nthames.nhs.uk
Subject: Re(2): 811A in audio
Date: Fri, 26 Sep 1997 18:54:43 +0100
Source: Sound Digest Archive v01.n044
Hi,
> > It has a very high mu and the
> > plate curves are not pretty; it was designed for positive grid bias.
>
> tube was never intended to be used this way (IMHO). As an RF linear
> amp they are kinda fun.
Certainly, but can we have some more Juice please? I remember that
russian mobile military tranmitter. We once accidentaly "mistuned"
the Aerial. It melted in an instant.I'm not sure which Valves (and
how many) that one used, but....
> They also make a great AM modulator in class B push-pull. It shows
> potential as a PP AB tube, but who needs 200 watts of PP DHT's?
If we can have that with zero-feedback, sorta of a slightly scaled
Version of Lynn Olsons P-P, I'll have one. My neigbours are way too
noisy and Watt/Puppy clones need a bit more than the 50W Solid-State
per channel they are fed on at the moment. Also, I have so far been
incapable of causing Structural Damage in my house and the Heating
is not so good.
Should work just dandy.
=========================================================================
From: Michel Paquette <paqm01@GEL.USherb.CA>
Subject: Re: 811A in audio
Date: Fri, 26 Sep 1997 15:58:41 -0400
Source: Sound Digest Archive v01.n045
Hello Match (I don't this is your actual name but I didn't find another...)
Thanks for the response. To tell you the thruth, I didn't know the 811
was meant for class B. I find this funny because (although I admit I
haven't seen the curves in a heck of long time), the curves showded mostly
positive grid bias curves; the negative bias curves were squeezed near the
0 current axis.
Best regards,
Michel
>Michel wrote:
>
>> I wouldn't design an amp around the 811.
>
>I've used these, I think there are better choices for SE, SV-572's
>come to mind, however they can be made to work better than the curves
>would suggest. Save yourself some hair-pulling by using an IT
>transformer, if you try this. The grid current will kill you
>otherwise.
>
>> It has a very high mu and the
>> plate curves are not pretty; it was designed for positive grid bias.
>>
>Almost true. It was designed to run in class B with NO bias.
>In order to run it in class A we need lots of positive bias, but the
>tube was never intended to be used this way (IMHO). As an RF linear
>amp they are kinda fun.
>
>They also make a great AM modulator in class B push-pull. It shows
>potential as a PP AB tube, but who needs 200 watts of PP DHT's?
=========================================================================
From: el34@juno.com (Joseph E Lowe)
Subject: Re: Re(2): 811A in audio
Date: Fri, 26 Sep 1997 16:28:36 -0400
Source: Sound Digest Archive v01.n045
>> They also make a great AM modulator in class B push-pull. It shows
>> potential as a PP AB tube, but who needs 200 watts of PP DHT's?
>
>If we can have that with zero-feedback, sorta of a slightly scaled
>Version of Lynn Olsons P-P, I'll have one.
The ultimate is a pair of 838's in Class B p-p. They will do 280W with
less than 5% distortion with zero feedback. They were designed for this
purpose, and have slightly variable Mu to get the low distortion. This
also explains their unique in your face sound when used SE.
The next step up is 833.
=========================================================================
From: "Mark Donen" <soledadd@worldnet.att.net>
Subject: 811 horns
Date: Tue, 2 Dec 1997 23:49:56 -0500
Source: Sound Digest Archive v01.n124
Does anyone have any experience of Altec 811 horns? I want to use a first
order xover but should it be at 500hz or the safer 800hz?
Can they be made to sound good? Do they ring if not treated? What coating
can be used?
Also what about Altec 1" compression drivers? What is the difference
between an 804/806/808?
TIA for any info.
Mark D
=========================================================================
From: Ron Steinberg <ca789@freenet.toronto.on.ca>
Subject: Re: 811 horns
Date: Wed, 3 Dec 1997 11:54:41 -0500 (EST)
Source: Sound Digest Archive v01.n124
On Tue, 2 Dec 1997, Mark Donen wrote:
> Does anyone have any experience of Altec 811 horns? I want to use a first
> order xover but should it be at 500hz or the safer 800hz?
I use an 811 horn in my Valencia's. They are meant to be crossed over at
800 Hz, but I was told by someone who really knows his stuff regarding
Altec that they resonate badly at 1100Hz, and he recommends crossing over
at 1200Hz to eliminate this. I built a new crossover (altec 1205-8A)
which crosses over at 1200Hz, and must say that they sounded MUCH better.
>
> Can they be made to sound good? Do they ring if not treated? What coating
> can be used?
>
Yes, they can really use some dampening. What I found to be effective is
a 1/2 inch strip of the new 3M viscoelastic dampening sheet, which is a
layer of thin elastomer bonded to a sheet of aluminum, applied to the
outer edge of the horn, the large curved front surface. When I did one
horn, and tapped it, it was a lot more 'dead' and didn't ring like the
one that I hadn't done. In listening to it, it sounded like it didn't
have as much high frequency extension, but I realized that the untreated
horn was just ringing, and didn't actually go up as high. If you use the
3M product, you really only need to apply a small amount, and do it at
the outer edge. 3M told me that they had done a test with a cymbol, one
was covered with the dampening product, the other only the outer edge.
Very little was gained by covering the entire surface. Guess it's the
'free' edge that resonates the most, and that's where you want to dampen it.
Hope this helps,
Ron
======================================================================
Ron Steinberg Photographer <ca789@torfree.net>
Though self employed, my opinions do not reflect those of my employer.
======================================================================
=========================================================================
From: David Home <tubehead@vcn.bc.ca>
Subject: 811 thread...
Date: Fri, 26 Sep 1997 10:35:48 -0700 (PDT)
Source: Sound Digest Archive v01.n044
AHH!! My server deleted all my saved mail yesterday and I lost
the thread about operating conditions for the 811 and 811A
before I was able to read them. If someone saved them, could
you please forward them to me at this location and CC: my work
account ( just to be sure ): dhome@creo.com.
Many many thanks, David
=========================================================================
From: Rick Francis <rfranci@uoft03.UTOLEDO.EDU>
Subject: Re: 811 thread... why Svetlana 811-3 or 811-10 or 572-10 are better
Date: Fri, 26 Sep 1997 15:15:19 -0400 (EDT)
Source: Sound Digest Archive v01.n045
Seems important to mention that the new Svetlana tubes are much easier to
design for as audio output tubes because the gain is so much lower: 3,
10, or 30, you pick. Maybe this was too obvious. But if anyone wants
some NOS RCA 811s, I've got some. Or maybe they are 811-A. Whatever.
The Svetlana webpage has some simple SE schematics.
Rick Francis, rfranci@uoft03.utoledo.edu
=========================================================================
From: el34@juno.com (Joseph E Lowe)
Subject: Re: 811 thread... why Svetlana 811-3 or 811-10 or 572-10 are better
Date: Fri, 26 Sep 1997 16:38:04 -0400
Source: Sound Digest Archive v01.n045
On Fri, 26 Sep 1997 15:15:19 -0400 (EDT) Rick Francis
<rfranci@uoft03.UTOLEDO.EDU> writes:
>Seems important to mention that the new Svetlana tubes are much easier
>to design for as audio output tubes because the gain is so much lower:
3,
> 10, or 30, you pick. Maybe this was too obvious.
Sort of. This thread is about using high Mu Class B RF tubes in SE,
which is totally different concept than the low Mu stuff.
Svetlana does have the 572-160 which is similar to the 811 when used in
SE audio.
=========================================================================
From: Bob Danielak <rdaniela@ew.lmms.lmco.com>
Subject: Re: 812 A -808
Date: Fri, 12 Dec 1997 12:59:21 -0500
Source: Sound Digest Archive v01.n133
Russell DeAnna wrote:
>
> I picked up a pair of NOS RCA 812As on Wednesday. I looked
> in my RCA tube manual and found no charts on any of the
> transmitter tubes.
>
> What's the difference between 811, 812, 813, 845? If anyone
> has references to good circuits using the 812, please let me
> know. My OPTs are Electro Print MTK5Bs -- 5k primary I believe.
>
> If anyone has a pair of NOS DHTs to trade for my 812s,
> let me know. I'm not sure I want to use the high voltages
> necessary with these tubes.
>
> BTW, I built a quick and dirty SE amp using the 6CK4 and the
> above OPTs. It sounds similar to the push-pull version of my
> 6CK4 amp but has more low-level information. (6SL7 driver)
> The bad side: this amp clips very easily. On many modern choral
> works (Part, Taverner, Gorecki) one channel will start
> crackling -- almost sounds like the cone is ripping. I assume
> that channel is clipping. Hmmm, maybe I've got a bad speaker?
>
> -Russell (torgd@lerc.nasa.gov)
hi russell,raul
this discussion applies to 812, 808, and sv572-30
(among others)
i played with the 812A a bit. it certainly can be used single
ended - so long as you don't mind class A2 operation.
i published a few different schematics on joe list
about a year or so, ago.
here's one that i found from last february:
- ------
circuit description:
the tranny drive approach i came up with uses a 10:1 step down.
since the secondary has to pass the cathode current of the output tube,
i invert the tranny winding so the cathode current of the driver tube
cancels the dc flux (i.e. 1/10th of the output tube cathode current).
one other novelty of my 812 design is that the required positive grid
bias is provided by ac-bypassed cathode of the driver tube (6sn7).
... a cute little balancing act.
ascii schematic: (350V)
. ________________________________________ 10k _________________ 450V
. | | |o |
. 40u 47k )|| ____GND )||
. | | )||( p )||(
. GND | )||(__________ c g l )||
. | )||o a r a___|
. | | t i t
. plate-----||---- plate h d e
. ------- grid |------ grid (13V) |
. | cath | cath--------------|
. 100k | 470k | |
. | 2.2k | 1.5k 500u
. |______ |_______________|_______|_______|_____GND
.
input stage 1/2 6sn7. unbypassed cathode resistor gives gain of approx.
8.
this means an input sensitivity (before overloading 2nd stage) of about
1.1vrms. bypassing 2.2k just about doubles the gain.
2nd stage 1/2 6sn7 with 10:1 step down tranny in the plate.
was shooting for about 250v peak swing at the plate for +/-25V drive
to the output tube.
output stage: 812 (or sv572-30, etc).
in this example an 812 will run at about 86mA at +13V bias. the cathode
bias
of the previous 6sn7 stage provides this voltage to the grid. it just so
happens that the 6sn7's plate current at this bias is 8.6mA
(exactly 1/10th of the cathode current
of the output tube).
since the winding polarities are reversed, net dc flux is cancelled.
actually, the cathode resistor value neglects the effects of grid
current
drawn. this means that for perfect dc flux balance the total effective
cathode resistance should be about 1.5k. for the 812 and sv811/572 it
seems
like the grid impedance is about 2k. i'll probably put a pot in for this
resistor and dial it in. since the grid current starts to become pretty
substantial with increasing positive bias with the right tube and B+
combination i may be able to delete the cathode resistor completely ;0
for this low voltage operating point you can use a 2.5k opt (80 - 100ma
dc)
for about 8W <0.5% D2 with a +/-25V grid swing. this load keeps your
plate voltage from going too low. below 200V the grid current starts to
go
up significantly - which could tend to starve out the drivers cathode
resistor.
looks like negative feedback - might not be a bad thing ?!
a 5k load would work too. 7.5W at practically 0% d2 with +/-25V grid
drive.
this load also allows for more grid swing if the driver can supply it.
maybe >10W with 30 to 35V peak grid drive.
- ------
this was sort of the predecessor of my SV572-30 amp at
http://www.geocities.com/TimesSquare/1965/se_sv572.html
you could use the circuits shown for the 572-30, as well.
just need to observe the plate dissipation rating of the 812 (45W).
so you could run it up to about 600V with zero bias.
grid drive or cathode drive. your choice. either way need a stiff
driver.
could use something like my sv811-10 amp driver at:
http://www.geocities.com/TimesSquare/1965/se_sv811.html
in fact, i retrofit the 812 into this amp for a while.
at about 400V B+ you need some positive bias (like in the circuit
above).
i tried between +10 and +20.
doesn't sound half bad...
hth,
bob.d.
=========================================================================
From: torgd@tolstoy.lerc.nasa.gov (Russell DeAnna)
Subject: 812 A
Date: Thu, 11 Dec 1997 18:04:23 -0500 (EST)
Source: Sound Digest Archive v01.n132
I picked up a pair of NOS RCA 812As on Wednesday. I looked
in my RCA tube manual and found no charts on any of the
transmitter tubes.
What's the difference between 811, 812, 813, 845? If anyone
has references to good circuits using the 812, please let me
know. My OPTs are Electro Print MTK5Bs -- 5k primary I believe.
If anyone has a pair of NOS DHTs to trade for my 812s,
let me know. I'm not sure I want to use the high voltages
necessary with these tubes.
BTW, I built a quick and dirty SE amp using the 6CK4 and the
above OPTs. It sounds similar to the push-pull version of my
6CK4 amp but has more low-level information. (6SL7 driver)
The bad side: this amp clips very easily. On many modern choral
works (Part, Taverner, Gorecki) one channel will start
crackling -- almost sounds like the cone is ripping. I assume
that channel is clipping. Hmmm, maybe I've got a bad speaker?
- -Russell (torgd@lerc.nasa.gov)
=========================================================================
From: "Daniel J. Marshall" <danmarshall@worldnet.att.net>
Subject: Re: 812 A
Date: Fri, 12 Dec 1997 06:44:14 -0800
Source: Sound Digest Archive v01.n132
Russell DeAnna wrote:
>
> I picked up a pair of NOS RCA 812As on Wednesday. I looked
> in my RCA tube manual and found no charts on any of the
> transmitter tubes.
>
> What's the difference between 811, 812, 813, 845? If anyone
> has references to good circuits using the 812, please let me
> know. My OPTs are Electro Print MTK5Bs -- 5k primary I believe.
>
> If anyone has a pair of NOS DHTs to trade for my 812s,
> let me know. I'm not sure I want to use the high voltages
> necessary with these tubes.
>
> BTW, I built a quick and dirty SE amp using the 6CK4 and the
> above OPTs. It sounds similar to the push-pull version of my
> 6CK4 amp but has more low-level information. (6SL7 driver)
> The bad side: this amp clips very easily. On many modern choral
> works (Part, Taverner, Gorecki) one channel will start
> crackling -- almost sounds like the cone is ripping. I assume
> that channel is clipping. Hmmm, maybe I've got a bad speaker?
>
> -Russell (torgd@lerc.nasa.gov)
Russel,
The 812A is a high mu triode intended for PP class B modulator service
or as a class C rf amplifier. You might want to thing twice, or maybe
three or four times before launching headlong into an amp project with
this tube. If a lot of power is what you are after, a pair is capable
of up to 340 watts in class B PP at a plate voltage of 1,500 volts.
The 13,200 ohms PP transformer might be a bit difficult to come by.
I don't have the curves, or full data either, so I would not
categorically say that it could not be used for class A, but I suspect
that it would not be highly satisfactory. However, the limited data I
do have does specify a negative bias voltage even for PP class B use
rather than zero bias as some tubes require, so who knows, maybe it
could be made to work, after a fashion. However, this type of tube, in
general, tends to have a rather high plate resistance. I would think it
would be much better to use a lo-mu triode for SE class A. Perhaps
others have had direct experience with this tube and can advise you more
expertly than I.
Dan Marshall
=========================================================================
From: "Daniel J. Marshall" <danmarshall@worldnet.att.net>
Subject: Re: 812 A
Date: Fri, 12 Dec 1997 07:08:47 -0800
Source: Sound Digest Archive v01.n133
Russell DeAnna wrote:
>
> I picked up a pair of NOS RCA 812As on Wednesday. I looked
> in my RCA tube manual and found no charts on any of the
> transmitter tubes.
>
> What's the difference between 811, 812, 813, 845? If anyone
> has references to good circuits using the 812, please let me
> know. My OPTs are Electro Print MTK5Bs -- 5k primary I believe.
>
> If anyone has a pair of NOS DHTs to trade for my 812s,
> let me know. I'm not sure I want to use the high voltages
> necessary with these tubes.
>
> BTW, I built a quick and dirty SE amp using the 6CK4 and the
> above OPTs. It sounds similar to the push-pull version of my
> 6CK4 amp but has more low-level information. (6SL7 driver)
> The bad side: this amp clips very easily. On many modern choral
> works (Part, Taverner, Gorecki) one channel will start
> crackling -- almost sounds like the cone is ripping. I assume
> that channel is clipping. Hmmm, maybe I've got a bad speaker?
>
> -Russell (torgd@lerc.nasa.gov)
Russel,
You inquired as to the differences between the 811A, 812A 813 and 845
which I overlooked in the previous reply. From the limited specs I
have, it appears that the 811A and the 812A are quite similar. The main
differences noted are that the 811A is specified to operate at zero
volts grid bias for PP class B service, while the 812A calls for minus
40 to 48 volts for a similar quiescent operating point. This would
suggest that the 812A indeed would be a better candidate than the 811A
for service as for low power class A amplifier. I am not saying that it
is a good candidate, rather that I don't have full specs at hand, nor
experience, but the limited data that I do have suggests that it would
be a "better" candidate than the 811A.
The 813 is a beam tetrode capable of up to 650 Watts Po in AB2.
Now the 845 is another story, the real deal from what I have heard about
it, though I do not have first hand experience. However, I do have the
data, including the plate curves and they are quite lovely indeed. The
book say (for SE):
15 watts at Vp of 750v and RL of 3400 ohms (Rp=1,700 ohms).
21 watts at Vp of 1,000v and RL of 9,000 ohms (Rp=1,900 ohms).
24 watts at Vp of 1,250v and RL of 16,000 ohms (Rp=2,100 ohms).
PP Po capability is up to 105 watts.
Dan Marshall
=========================================================================
From: torgd@tolstoy.lerc.nasa.gov (Russell DeAnna)
Subject: Re: 812 A
Date: Fri, 12 Dec 1997 13:54:21 -0500 (EST)
Source: Sound Digest Archive v01.n133
Daniel M. wrote:
>
> The 812A is a high mu triode intended for PP class B modulator service
> or as a class C rf amplifier. You might want to thing twice, or maybe
> three or four times before launching headlong into an amp project with
> this tube. If a lot of power is what you are after, a pair is capable
> of up to 340 watts in class B PP at a plate voltage of 1,500 volts.
> The 13,200 ohms PP transformer might be a bit difficult to come by.
I found someone with characteristic curves who verified the above and
added some new information. Recommended plate voltage is 1250V with
a grid bias of -40V, and plate current of 250mA. Amplification factor
is 29 and filament voltage is 6.3V. The killer for me seems to be the
high plate resistance since my OPTs recommend 5k. And I don't want to
parallel the tubes.
If the OPT problem could be solved, any ideas for driver stages? Would
a simple 6SN7 be enough?
- -Russell (torgd@lerc.nasa.gov)
=========================================================================
From: Bob Danielak <rdaniela@ew.lmms.lmco.com>
Subject: Re: 812 A
Date: Fri, 12 Dec 1997 15:47:02 -0500
Source: Sound Digest Archive v01.n133
Russell DeAnna wrote:
>
> Daniel M. wrote:
> >
> > The 812A is a high mu triode intended for PP class B modulator service
> > or as a class C rf amplifier. You might want to thing twice, or maybe
> > three or four times before launching headlong into an amp project with
> > this tube. If a lot of power is what you are after, a pair is capable
> > of up to 340 watts in class B PP at a plate voltage of 1,500 volts.
> > The 13,200 ohms PP transformer might be a bit difficult to come by.
>
> I found someone with characteristic curves who verified the above and
> added some new information. Recommended plate voltage is 1250V with
> a grid bias of -40V, and plate current of 250mA. Amplification factor
> is 29 and filament voltage is 6.3V. The killer for me seems to be the
> high plate resistance since my OPTs recommend 5k. And I don't want to
> parallel the tubes.
>
> If the OPT problem could be solved, any ideas for driver stages? Would
> a simple 6SN7 be enough?
>
> -Russell (torgd@lerc.nasa.gov)
a 5K OPT ought to be fine, so long as it can handle 80-100mA.
the inductance should be in the 35-40H range, so LF response shouldn't
be too much of an issue.
plate loading rules are a bit different for Class A2...
see my other posts on the subject for some details.
let me know if i can help...
bob.d.
=========================================================================
From: Kalman Rubinson <rubinsnk@is2.nyu.edu>
Subject: 812a
Date: Tue, 30 Dec 1997 14:15:11 -0500 (EST)
Source: Sound Digest Archive v01.n147
Found a pair of these RCA bottles. Anyone interested?
Kal
=========================================================================
From: dslagle@earthlink.net (dave slagle)
Subject: Re: 8223 types
Date: Mon, 4 Jan 1999 15:40:32 -0500
Source: Sound Digest Archive v01.n558
>
> The plate curves for the E288CC/8223 look more like those of the E182CC/
>7119 and pretty good at high currents.
>
yeah, and there is a nifty shield between the two 1/2's I have yet to find
them at an affordable price...
dave
=========================================================================
From: dslagle@earthlink.net (Dave Slagle)
Subject: 8233
Date: Sun, 8 Nov 1998 09:46:50 -0800 (PST)
Source: Sound Digest Archive v01.n484
Hey,
anyone have the scoop on the 8233 (triod wired) just picked up a handfull...
looks pretty cool
thanks
dave
=========================================================================
From: Grego Sanguinetti <grego@lscpdx.latticesemi.com>
Subject: Re: 8233
Date: Mon, 9 Nov 1998 15:14:33 -0800
Source: Sound Digest Archive v01.n484
On Sun, Nov 08, 1998 at 09:46:50AM -0800, Dave Slagle wrote:
> Hey,
>
> anyone have the scoop on the 8233 (triod wired) just picked up a handfull...
You lucky dog!
We had a little discussion on these some time back.
They also go by the European nomenclature of E55L.
Basically they are like a magnoval, beefed up 7788.
kind of like the relationship between a 417a and a 437a if you like.
A very nice tube indeed. Make excellent drivers, potato amps
or headphone amps. Extremely low distortion, low Rp, high Mu,
10w plate dissipation...
> looks pretty cool
Yeah, made like a space ship.
The pair I have I baught simply because of the looks. I just knew
it had to be a good tube. Fortunately it turned out to be true.
So Dave, old buddy, think a pair could fly my way? B^)
- -grego
=========================================================================
From: Grego Sanguinetti <grego@lscpdx.latticesemi.com>
Subject: Re: 8233
Date: Wed, 11 Nov 1998 14:11:33 -0800
Source: Sound Digest Archive v01.n487
> >A very nice tube indeed. Make excellent drivers, potato amps
> >or headphone amps. Extremely low distortion, low Rp, high Mu,
> >10w plate dissipation...
>
> I am looking for small decent output trannies.........
>
> Guido
They run about 600ohms or so, very low impedance
so finding an output tranny is mainly a question
of current and secondary impedance. If you are lucky
enough to have 600ohm headphones then the selection
is a little better. But you need something that can
handle 50+mA.
When I was comparing sonics of various drivers,
I used the Sowter 8423 IT and just loaded the
secondaries with I believe a 100K resistor and
hooked up my headphones (which are 32ohms) across
that. The E55L sounded great. Hmmm, maybe I will
hook that up again in a box, I need another
can amp.... I have an extra pair of 2k IT's
and they would probably work...B^)
My setup was an 0D3 regulated B+ of about 130v.
I stacked it on 2 NiCads and ended up with close
to 60mA. Now this is not only 2x the transformer
rating (which it handled admirably, thanks Brian)
but also is pushing the tube too hard. But it
sounded great. I would suggest upping the
bias for a sustained effort.
The operating point that Tom Dunker suggested
was Vp=125, Vg=-3v, for Ip=55mA from memory so
I hope that is correct. So I was running the
plate a bit higher and the bias a bit lower.
You could run a plate to line transformer in
parallel feed as an option.
- -grego
=========================================================================
From: evaguido <EvaGuido@iaehv.nl>
Subject: Re: 8233
Date: Wed, 11 Nov 1998 20:16:52 +0100
Source: Sound Digest Archive v01.n487
At 15:14 9-11-98 -0800, Grego Sanguinetti wrote:
>
>On Sun, Nov 08, 1998 at 09:46:50AM -0800, Dave Slagle wrote:
>> Hey,
>>
>> anyone have the scoop on the 8233 (triod wired) just picked up a
handfull...
>
>You lucky dog!
>
>We had a little discussion on these some time back.
>They also go by the European nomenclature of E55L.
ah, that ones: yes he's lucky !
>Basically they are like a magnoval, beefed up 7788.
>kind of like the relationship between a 417a and a 437a if you like.
>
>A very nice tube indeed. Make excellent drivers, potato amps
>or headphone amps. Extremely low distortion, low Rp, high Mu,
>10w plate dissipation...
I am looking for small decent output trannies.........
Guido
>> looks pretty cool
>
>Yeah, made like a space ship.
>The pair I have I baught simply because of the looks. I just knew
>it had to be a good tube. Fortunately it turned out to be true.
>So Dave, old buddy, think a pair could fly my way? B^)
>
>-grego
>
>
=========================================================================
From: Paul Joppa <pdj@ISDNseattle.net>
Subject: Re: 8233
Date: Wed, 11 Nov 1998 20:49:33 -0800
Source: Sound Digest Archive v01.n487
Grego Sanguinetti wrote:
> ...snip...
> They run about 600ohms or so, very low impedance
> so finding an output tranny is mainly a question
> of current and secondary impedance. If you are lucky
> enough to have 600ohm headphones then the selection
> is a little better. But you need something that can
> handle 50+mA.
> ...snip...
> My setup was an 0D3 regulated B+ of about 130v.
> I stacked it on 2 NiCads and ended up with close
> to 60mA.
...snip...
Can they run as high as 200v/50mA? (I think 10 watts was mentioned...)
then a TFA-204 would fit well. I have them in my 2A3 amps, they're a
very sweet transformer but they don't like more than 60mA and really
like less - I run 55; tried 70 once & didn't like it at all. They're
also a little light in the inductance, so a low-Z plate is in order,
600 ohms is very attractive.
- -Paul Joppa
=========================================================================
From: "Larry D. Moore" <l-moore@onu.edu>
Subject: 8233
Date: Sun, 15 Nov 1998 08:56:52 -0500
Source: Sound Digest Archive v01.n491
Gang:
I was at Fair Radio yesterday and they have a large number of 8233 pulls at
$8.00 each. Most are Amperex or PQ Amperex. I also believe I saw some
Mullards in the box as well. Now is you big chance for the super coll
spud'zilla amp.
=========================================================================
From: dslagle@earthlink.net (dave slagle)
Subject: Re: 8233
Date: Sun, 15 Nov 1998 10:10:10 -0500
Source: Sound Digest Archive v01.n491
oh sure larry tell the masses....
anyways, I believe that the mullards and the amperexes (at least the ones I
have are the same tube and made in great britain.
aside from a spudzilla, I wonder how to use these puppies.
the high current they require makes them inappropriate for resistor loading
so that leaves us the good old choke load.
I suppose a simple choke loaded cap coupled driver for a 300B would be a
cool way to work these puppies, but you might have problems getting full
output...without running into all of the other problems associated with the
high Gm tubes...(contact potenetial, drive requirements) if they even are a
problem.
It sure seems like using them with output iron is a match made in heaven,
but I still see the problems I had with the single 417 and 437 amps... you
just don't get enough swing!
biased at -3V you will need a lot of drive to get that 1.5W out which means
the average CD out or phono stage out won't do it, so you rely on your
linestage which essentially forms a two stage amp with way too much gain...
so you use a 26 or 27 linestage to give you the appropriate gain and that
sweet sound we like, and all of the gain stages are in line no waste no
worry.
the idea of a single stage amp is really sort of a weird thing... it seems
like a marketing tool... I think we all have to step back and talk about
our entire gain structure and forget about the boxes they sit in. at one
point we have to compromise if we have several sources, to avoid drastic
level changes when source swapping, but beyond that...
I love the idea of a potato amp! it gave me my first SE experience, but it
was driven by a PAS so in essence it was the same as a 12AX7-12AX7-tons o'
of feedback 417A amp, but since they were on different chassis i could
brag to my friends on the purity of the amp... i even fooled myself for a
while... things have changed a lot since then, but like most of us... I am
probably still fooling myself.
dave
=========================================================================
From: Patrick Currie <tubesguy@chorus.net>
Subject: Re: 8233
Date: Sun, 15 Nov 1998 10:59:02 -0600
Source: Sound Digest Archive v01.n491
>oh sure larry tell the masses....
>
>anyways, I believe that the mullards and the amperexes (at least the ones I
>have are the same tube and made in great britain.
>
>aside from a spudzilla, I wonder how to use these puppies.
>dave
Call me crazy, but how about using it as a driver in, gasp, pentode mode?
It is a pentode, right? Talk to Levreault about pentode drivers. Of
course he uses them for 300B-type amps, not 45s.
I still have fond memories of the first pentode driver 300B amp I heard.
And that was just a 6SJ7 driving a Chinese 300B. A better pentode driving
a better output tube? Hmmm ... - Pat
PS - Pack by 17
=========================================================================
From: "Doc B." <bottlehead@silverlink.net>
Subject: Re: 8233
Date: Sun, 15 Nov 1998 14:34:49 -0800
Source: Sound Digest Archive v01.n491
>You're reading my mind here, Pat. My only reluctance is that this is a
>low-voltage tube (ep = 200V max, according to my GE Essentials), but this
should
>be fine for 45 or 2A3, where you only need about 50Vpk of grid drive.
>
Hey, just a gol durned minute!
The Levrault I know would never say 50V was enough drive for a tube with 45V
of bias. He'd want at least 90V.
Who are you, you imposter?
Doc B., LMAO
=========================================================================
From: John Levreault <jlevro@mediaone.net>
Subject: Re: 8233
Date: Sun, 15 Nov 1998 16:09:15 -0500
Source: Sound Digest Archive v01.n491
Patrick Currie wrote:
> Call me crazy, but how about using it as a driver in, gasp, pentode mode?
> It is a pentode, right? Talk to Levreault about pentode drivers. Of
> course he uses them for 300B-type amps, not 45s.
>
> I still have fond memories of the first pentode driver 300B amp I heard.
> And that was just a 6SJ7 driving a Chinese 300B. A better pentode driving
> a better output tube? Hmmm ... - Pat
You're reading my mind here, Pat. My only reluctance is that this is a
low-voltage tube (ep = 200V max, according to my GE Essentials), but this should
be fine for 45 or 2A3, where you only need about 50Vpk of grid drive.
I have used pentodes with 45's, and they work real well together, especially the
6AC7. Unfortunately, 45's just don't have enough power for me, so my experience
with them is limited, but their sweet tone sure makes me long for some
high-sensitivity speaks.
I say give it a try.
JL
=========================================================================
From: John Levreault <jlevro@mediaone.net>
Subject: Re: 8233
Date: Sun, 15 Nov 1998 19:21:55 -0500
Source: Sound Digest Archive v01.n491
"Doc B." wrote:
> >You're reading my mind here, Pat. My only reluctance is that this is a
> >low-voltage tube (ep = 200V max, according to my GE Essentials), but this
> should
> >be fine for 45 or 2A3, where you only need about 50Vpk of grid drive.
> >
>
> Hey, just a gol durned minute!
> The Levrault I know would never say 50V was enough drive for a tube with 45V
> of bias. He'd want at least 90V.
> Who are you, you imposter?
Thanks for picking that up, Doc. But I was actually figuring on a 100V peak
(200V pk-pk) swing with the full 200V ep. So there. Of course, if I had the
curves, I'd be able to guess a bit better. Maybe you can get that 100V peak
swing at a slightly lower ep. But anything less would be "dynamically
challenged".
JL
=========================================================================
From: "Larry D. Moore" <l-moore@onu.edu>
Subject: Re: 8233
Date: Sun, 15 Nov 1998 20:15:01 -0500
Source: Sound Digest Archive v01.n492
Hey, you know me. I always spill the beans..:>) Actually, IMHO you hit
the nail on the head with these tubes. Swing is the major problem.
Ultimately it will be dynamically challenged. It also will never have that
DHT sound. A 26 up front can help this though. I agree with the total
gain approach, or maybe drive approach. To me it helps one kick a bunch of
bad habits. One should relly build this amp for a sense of perspective.
It is a great tool for learning what things do and don't sound like by
removing a bunch of stuff from the amp. In this, it is worth its weight in
gold. A building block of knowledge once under your belt will help for
years to come. If there are any flegling amp designers out there lurking,
build this! You will learn.
Larry
At 10:10 AM 11/15/98 -0500, dave slagle wrote:
>oh sure larry tell the masses....
>
>anyways, I believe that the mullards and the amperexes (at least the ones I
>have are the same tube and made in great britain.
>
>aside from a spudzilla, I wonder how to use these puppies.
>
>the high current they require makes them inappropriate for resistor loading
>so that leaves us the good old choke load.
>
>I suppose a simple choke loaded cap coupled driver for a 300B would be a
>cool way to work these puppies, but you might have problems getting full
>output...without running into all of the other problems associated with the
>high Gm tubes...(contact potenetial, drive requirements) if they even are a
>problem.
>
>It sure seems like using them with output iron is a match made in heaven,
>but I still see the problems I had with the single 417 and 437 amps... you
>just don't get enough swing!
>
>biased at -3V you will need a lot of drive to get that 1.5W out which means
>the average CD out or phono stage out won't do it, so you rely on your
>linestage which essentially forms a two stage amp with way too much gain...
>so you use a 26 or 27 linestage to give you the appropriate gain and that
>sweet sound we like, and all of the gain stages are in line no waste no
>worry.
>
>the idea of a single stage amp is really sort of a weird thing... it seems
>like a marketing tool... I think we all have to step back and talk about
>our entire gain structure and forget about the boxes they sit in. at one
>point we have to compromise if we have several sources, to avoid drastic
>level changes when source swapping, but beyond that...
>
>I love the idea of a potato amp! it gave me my first SE experience, but it
>was driven by a PAS so in essence it was the same as a 12AX7-12AX7-tons o'
>of feedback 417A amp, but since they were on different chassis i could
>brag to my friends on the purity of the amp... i even fooled myself for a
>while... things have changed a lot since then, but like most of us... I am
>probably still fooling myself.
>
>dave
>
>
>
>
=========================================================================
From: Grego Sanguinetti <grego@lscpdx.latticesemi.com>
Subject: Re: 8233
Date: Mon, 16 Nov 1998 14:16:51 -0800
Source: Sound Digest Archive v01.n493
Thanks Larry! I just ordered some. I only had one pair and
was looking for some extras. Currently being light of cash
these pulls are a good find.
On Sun, Nov 15, 1998 at 04:09:15PM -0500, John Levreault wrote:
> Patrick Currie wrote:
>
> > Call me crazy, but how about using it as a driver in, gasp, pentode mode?
> > It is a pentode, right? Talk to Levreault about pentode drivers. Of
> > course he uses them for 300B-type amps, not 45s.
> >
> > I still have fond memories of the first pentode driver 300B amp I heard.
> > And that was just a 6SJ7 driving a Chinese 300B. A better pentode driving
> > a better output tube? Hmmm ... - Pat
>
> You're reading my mind here, Pat. My only reluctance is that this is a
> low-voltage tube (ep = 200V max, according to my GE Essentials), but this should
> be fine for 45 or 2A3, where you only need about 50Vpk of grid drive.
No worries! I have tried it and it works fine. I tried it in
the B52 driver setup. You can swing more than twice the Vp.
Use the Sowter 8423. Hook the secondaries up in series.
Yes you will be violating the primary current spec
Yes you will be running the IT in 1:2 step up mode.
It should fall apart...
But it works B^)
The big Tango IT's should be glorious also.
I didn't have any 8233's when I did my initial comparisions
and distortion tests so I don't have hard data on the
8233 but the scope waveform still looked good at high output.
Plus it is quite smooth going positive so you can
overdrive it's bias without the world comming apart.
My experience with both the 7788 and 8233 is that the
output tubes crap out long before these drivers do.
The VV52s fold up long before the driver does in the
B52 amps.
Of course the 7788 has more gain than the 8233 but
the 8233 has more grunt. Between the two of them you
can drive just about anything.
Hey, and, they sound good too. B^)
I have no experience with either one as potato amp though.
By the way. No need to run these in pentode, they work
much better in triode and they push plenty of
volts and milliamps so why muck with it.
These high gm tubes aren't for everybody but I think
you will have alot less issues with these pentodes
than with the 417a and 437a.
One thing to be aware of though is that there is some
variation between lots. They are very high strung tubes
and the very slightest of variation in manufacturing makes
a big difference in their bias so be sure to not design at
their extremes.
For instance, I ended up dropping the Vp on the 7788's by
changing one of the 0C3's to an 0A3. Some lots of 7788's
were pretty hot and would run away at the higher Vp. At
the same Vp,Vg and Rl, some would run at 25ma and some
at 55ma! By lowering Vp to around 180v all the different
7788's I had would still run inside their sonic sweet
spot, which is 20-35mA (amazingly forgiving).
- -grego
=========================================================================
From: Paul Joppa <pdj@ISDNseattle.net>
Subject: Re: 8233
Date: Tue, 17 Nov 1998 17:59:43 -0800
Source: Sound Digest Archive v01.n494
OK, this is from a couple days ago, but I couldn't pass it up after
all...
dave slagle wrote:
> ...big snip...
> the idea of a single stage amp is really sort of a weird thing... it seems
> like a marketing tool... I think we all have to step back and talk about
> our entire gain structure and forget about the boxes they sit in. at one
> point we have to compromise if we have several sources, to avoid drastic
> level changes when source swapping, but beyond that...
>
> I love the idea of a potato amp! it gave me my first SE experience, but it
> was driven by a PAS so in essence it was the same as a 12AX7-12AX7-tons o'
> of feedback 417A amp, but since they were on different chassis i could
> brag to my friends on the purity of the amp... i even fooled myself for a
> while... things have changed a lot since then, but like most of us... I am
> probably still fooling myself.
I think the most attractive idea is a spud with a volume control,
directly driven from a CD. With the right CD player, you can have a
playback chain with only the power supply capacitor; using a regulator
can get you no caps at all.
- -Paul Joppa
=========================================================================
From: dslagle@earthlink.net (Dave Slagle)
Subject: Re: 8233
Date: Tue, 17 Nov 1998 20:30:58 -0800 (PST)
Source: Sound Digest Archive v01.n495
>I think the most attractive idea is a spud with a volume control
Is there any other way???
>directly driven from a CD.
assuming the CD has the lev-head-room-fer-y'all... I had a 5687 IT coupled
to a 5687 blow a spud away... too many other variables to comment on, but i
learned something.
>With the right CD player you can have a
>playback chain with only the power supply capacitor.
which CD player is that??? I will agree with the basic thought, when I
glommed on a trannie to the output of my first generation cheap ass dde
1.0, I lost a cap and the sound got better, but there are still a bunch of
those pesky condensers... the input cap for example... tried to lose it, no
luck yet, but I'm still trying.
I guess the point I was trying to make... It all matters from the lips of
the artist or the pluck of a gut to the wet mass of goo we call our
brain... everything inbetween matters. Don't get me wrong, a potato is a
great amp... my attempts taught me alot, and as a learning tool they are
great... hell they should be required building... but they can also be
improved upon when you look at the total structure of the system, and put
that beautiful simplistic potato STAGE with a few more to make music.
>using a regulator
>can get you no caps at all.
and as a scientiffic endeavor its novel, but why not hire a string quartet
and get no electronics at all...
dave
=========================================================================
From: Grego Sanguinetti <grego@lscpdx.latticesemi.com>
Subject: Re: 8233
Date: Wed, 18 Nov 1998 09:55:50 -0800
Source: Sound Digest Archive v01.n495
On Tue, Nov 17, 1998 at 08:30:58PM -0800, Dave Slagle wrote:
> from Pablo Jappa-son:
> >I think the most attractive idea is a spud with a volume control
> >directly driven from a CD.
> ...
> >With the right CD player you can have a
> >playback chain with only the power supply capacitor.
>
> which CD player is that??? I will agree with the basic thought, when I
> glommed on a trannie to the output of my first generation cheap ass dde
> 1.0, I lost a cap and the sound got better, but there are still a bunch of
> those pesky condensers... the input cap for example... tried to lose it, no
> luck yet, but I'm still trying.
Hmm, this is normally a problem of DC offset from the source, especially
if the input stage of your amp has fixed bias (or battery cathode bias).
The DC offset screws up your bias. However this is odd because you imply
that the output of your source is coupled through a transformer? I would
not expect DC offset.
- -grego
=========================================================================
From: "T. Loesch" <ezee_e@hotmail.com>
Subject: Re: 8233
Date: Wed, 18 Nov 1998 10:26:24 PST
Source: Sound Digest Archive v01.n495
Hi there,
>> >With the right CD player you can have a
>> >playback chain with only the power supply capacitor.
>>
>> which CD player is that???
You could try the Marantz CD-67 SE in it's "Thunderstone" hot-rod
Version.
No Series Capacitors, only three high quality shunt-capacitors and very
high quality PSU Cap's....
Se the Article by your's truely in TNT-Audio....
Kind regards Thorsten.
======================================
e-mail:
Thorsten@tnt-audio.com
Visit TNT-Audio on the Web - the only advertising
free audio web-zine.
http://www.tnt-audio.com
======================================
______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com
=========================================================================
From: dslagle@earthlink.net (dave slagle)
Subject: Re: 8233
Date: Wed, 18 Nov 1998 15:10:36 -0500
Source: Sound Digest Archive v01.n495
>
>Hmm, this is normally a problem of DC offset from the source, especially
>if the input stage of your amp has fixed bias (or battery cathode bias).
>The DC offset screws up your bias. However this is odd because you imply
>that the output of your source is coupled through a transformer? I would
>not expect DC offset.
sorry, to clarify, I attempted losing the cap at the input of the D2A
converter by replacing it with an input trannie, (LD moore dac attackin
valve) couldn't get it to lock properly, I assume since the signal is
digital at the input the trannie provides isolation, in other words the cap
doesn't color the sound, but passes lots of garbage. The transformer on
the output does indeed block the dc and did get rid of a cap, leaving the
signal from the output of the processor free of any coupling capacitors, in
fact the only caps are PS caps... there are 4 transformers tho'
dave
=========================================================================
From: "Richard A. Francis" <rfranci@uoft03.utoledo.edu>
Subject: Re: 8233 or any other tube for SPUD AMP for Dyna PAS preamp chassis (Dynah Moe Hum)
Date: Tue, 15 Dec 1998 16:34:39 -0500 (EST)
Source: Sound Digest Archive v01.n540
On Tue, 17 Nov 1998, Paul Joppa wrote:
> I think the most attractive idea is a spud with a volume control,
> directly driven from a CD. With the right CD player, you can have a
> playback chain with only the power supply capacitor; using a regulator
> can get you no caps at all.
>
I have a Dyna PAS with a blown PT (hamfest). I was staring at it last
night, trying to figure out what to do with it. I thought, I'll never play
a turntable through this. I might as well scrap the phono board. I have a
nice little PT that would fit fine in there, and it has a 5V rectifier
winding -- could put a 5V4 in there. a little filter choke, use
the miniaturized TSHA filter caps, and I'd STILL have some room left over.
Then I thought, why not make this something I would USE! How about a
single-tube amp with input selector and volume control? Maybe I'd add a
headphone jack later...
I've got a couple WE417s, and also two 8233s, gobs of parts, including
some useable SE OPTs. Or could do a 6DN7 deal. (S.E.X. in a box: Dynah
Moe Hum? apologies to Frank Zappa and Doc Bottlehead)
Or I could use the 12AX7 board to drive SE 6BQ5s?????
Any ideas, anecdotes, schematics, or warnings really really really
welcome.
Rick
=========================================================================
From: Paul Joppa <pdj@ISDNseattle.net>
Subject: Re: 8233 or any other tube for SPUD AMP for Dyna PAS preamp chassis (Dynah Moe Hum)
Date: Tue, 15 Dec 1998 22:47:27 -0800
Source: Sound Digest Archive v01.n541
OK, Rick, we gotta know the transformer B+ voltage. Assuming the usual
300-350v range, here's a couple ideas:
417 (or 8233 triode-wired?) with a current-source load, parafeed out
(both these tubes want lowish voltages)
I have a 6DN7 direct-coupled design in work, hopefully after Christmas
I'll get one built. Very attractive as an experimental base, there are
cheap interstages that can work with it, or as choke-loaded driver,
or resistive load, plus parafeed or transformer-coupled outputs, plus
...
The 12AX7 can drive 6BQ5s in pentode mode (no Miller capacitance) but
triode-wired you probably want something beefier - an AT7 at least.
Don't need the gain though, anything with a mu over 5 should do OK...
a 6BQ5 can use the same o/p trannie (5kohms) as a 6DN7 or 417A.
- -Paul Joppa
Richard A. Francis wrote:
> ...snip
> I have a Dyna PAS with a blown PT (hamfest). I was staring at it last
> night, trying to figure out what to do with it. I thought, I'll never play
> a turntable through this. I might as well scrap the phono board. I have a
> nice little PT that would fit fine in there, and it has a 5V rectifier
> winding -- could put a 5V4 in there. a little filter choke, use
> the miniaturized TSHA filter caps, and I'd STILL have some room left over.
>
> Then I thought, why not make this something I would USE! How about a
> single-tube amp with input selector and volume control? Maybe I'd add a
> headphone jack later...
>
> I've got a couple WE417s, and also two 8233s, gobs of parts, including
> some useable SE OPTs. Or could do a 6DN7 deal. (S.E.X. in a box: Dynah
> Moe Hum? apologies to Frank Zappa and Doc Bottlehead)
>
> Or I could use the 12AX7 board to drive SE 6BQ5s?????
>
> Any ideas, anecdotes, schematics, or warnings really really really
> welcome.
=========================================================================
From: "Richard A. Francis" <rfranci@uoft03.utoledo.edu>
Subject: Re: 8233 or any other tube for SPUD AMP for Dyna PAS preamp chassis (Dynah Moe Hum)
Date: Wed, 16 Dec 1998 05:54:36 -0500 (EST)
Source: Sound Digest Archive v01.n541
On Tue, 15 Dec 1998, Paul Joppa wrote:
> OK, Rick, we gotta know the transformer B+ voltage. Assuming the usual
> 300-350v range, here's a couple ideas:
Well here's the beauty, and the source of my (usual) paralysis: there IS
no PT in there yet, and I've got lots to choose from, including some that
with a FW bridge would be in the neighborhood of your 6DN7
direct-coupled... I went back and looked at Dave Dintenfass's spud amp,
read Doc B.'s tweaks for it, and looked at Ron Welbourne's parafeed 6EM7
schematic. I think I'll try a cheap version here (meaning I'll recycle
some console SE 6BQ5 opts), which means I won't need a lot of space for
output iron -- ought to fit fine where the phono board is in the Dyna.
> 417 (or 8233 triode-wired?) with a current-source load, parafeed out
> (both these tubes want lowish voltages)
>
I like the idea of using that 8233 here, but might be a tad tall for the
Dyna PAS case. In any case I'm planning to punch vent holes over the
output tubes, put a piece of mesh in there...
> I have a 6DN7 direct-coupled design in work, hopefully after Christmas
> I'll get one built. Very attractive as an experimental base, there are
> cheap interstages that can work with it, or as choke-loaded driver,
> or resistive load, plus parafeed or transformer-coupled outputs, plus
> ...
>
Cool! Keep us informed.
Rick
=========================================================================
From: davidbarnett@aristotle.net (David Barnett)
Subject: Re: 8233 or any other tube for SPUD AMP for Dyna PAS preamp chassis (Dynah Moe Hum)
Date: Wed, 16 Dec 1998 19:14:03 GMT
Source: Sound Digest Archive v01.n542
On Tue, 15 Dec 1998 16:34:39 -0500 (EST), "Richard A. Francis"
<rfranci@uoft03.utoledo.edu> wrote:
>Then I thought, why not make this something I would USE! How about a
>single-tube amp with input selector and volume control? Maybe I'd add a
>headphone jack later...
And to think that I used to look at the SCA-35 and think about
building a PREAMP in it. I can see that our impulses run 180-degrees
out from each others'.
- --dnb
=========================================================================
From: MHuber@t-online.de (Manfred Huber)
Subject: 830B data anyone?
Date: Thu, 15 Jan 98 10:07:11 -0100
Source: Sound Digest Archive v01.n162
Hi JoeNetters,
I'm looking for plate curves and operating points
for the 830B. I have found some data in the RCA TT-5
but this is not enough to decide if this tube is
usable for my purpose.
Regards
Manfred
- ------------------
Manfred Huber
MHuber@t-online.de
- ------------------
=========================================================================
From: slagle@dtlweb.com (Dave Slagle)
Subject: 83 blue glow....
Date: Mon, 10 Nov 1997 11:54:44 -0500 (EST)
Source: Sound Digest Archive v01.n104
hey all...
One of my 83's is starting to glow more than the rest.... I first noticed
this a few weeks ago, and since then the blue has been steadily
increasing...to the point where it is starting to look like an OD3... all
my other 83's have considerably less color... I am guessing it is just
nearing the end of it's life, which would suck, cuz it really looks cool!
any thoughts / experiences????
dave
=========================================================================
From: Robert Ang <rang@opera.iinet.net.au>
Subject: 83s (again)
Date: Sat, 04 Apr 1998 23:06:45 +0800
Source: Sound Digest Archive v01.n244
Sorry to bring up an old topic again, but only today did I get my hot
little hands on 2 NOS RCA 83 mercury vapour rectifiers. They are US
Navy 1942 NOS tubes, beautifully made - I'm proud to own them! Anyway,
the principle reason why I want to use them is because of the
interesting case reports from the JoeList, that low impedence rectifiers
DO make a difference. However, I have concerns on several problems with
their implication:
1. How does everyone overcome the problems with radiating RF from the
rectifier? My friend has used them in the past, but now refuses to use
them because he says his tuner in the car parked outside actually starts
screwing up when he turns on the rectifier. Surely this RF is a serious
problem with sensitive circuits nearby, especially digital circuits in
CD players and DACs.
2. Since the valve needs to be preheated, do people normally use a
timing circuit to turn it on or just have two manual switches for
separate filament and plate transformers?
3. I'm not sure if you all realise this, but mercury vapour rectifiers
actually give off a lot of invisible UV light. From memory, they give
off a lot of UV type B, which some of you may know is more strongly
correlated to melanoma than UV-A (which does most of the burning and
sunburn, but is not as strongly related to melanoma). This is a
concern. Also this UV predisposes to cataracts, so if any of you guys
love staring into the romantic glow of your 83 mercury vapour rectifiers
sitting in your SE amps, then you may be inadvertently damaging your
eyes. Note that this is a long term effect, and something best avoided.
Thus, from the above concerns, see if this recommendation makes sense:
Put the 83 in an enclosed, shielded box with ventilation holes for
cooling. This box can act as a separate power supply with umbilicals
running to your amp or pre-amp. Have two switches, one which switches
the filament on first, and allow this to warm up for several minutes
before switching on the plate voltage.
Any comments?
Rob.
- --
Another message from Robert Ang.
AudioGenesis
Where True Hi-Fi begins.
http://opera.iinet.net.au/~rang
=========================================================================
From: Dan Kerl <dlkerl@ro.com>
Subject: Re: 83s (again)
Date: Mon, 06 Apr 1998 08:16:32 -0500
Source: Sound Digest Archive v01.n246
Robert Ang wrote:
>
>
> 3. I'm not sure if you all realise this, but mercury vapour rectifiers
> actually give off a lot of invisible UV light. From memory, they give
> off a lot of UV type B, which some of you may know is more strongly
> correlated to melanoma than UV-A (which does most of the burning and
> sunburn, but is not as strongly related to melanoma). This is a
> concern. Also this UV predisposes to cataracts, so if any of you guys
> love staring into the romantic glow of your 83 mercury vapour rectifiers
> sitting in your SE amps, then you may be inadvertently damaging your
> eyes. Note that this is a long term effect, and something best avoided.
Since the 83 envelope is made of glass instead of quartz, most short wave
(2300 angstrom range) UV won't get through it. I wouldn't think you'd
have that much to worry about.
- --
Dan Kerl
dlkerl@ro.com
Pursuant to US Code, Title 47, Chapter 5, Subchapter II, Sec. 227, any
and all unsolicited commercial e-mail sent to this address is subject
to a download and archival fee in the amount of $500 (U.S.);
unsolicited use denotes acceptance of these terms.
=========================================================================
From: An-shyang Chu <achu@sandia.gov>
Subject: Re: 83s (again)
Date: 06 Apr 1998 08:34:31 -0600
Source: Sound Digest Archive v01.n246
Hi Rob,
But the glass envelope should suck up ~ 99.9% of those UV light. Regular glass
(unlike quartz, synthetic fused silica, which are $$!) does not transmit UV very
well. (One has to pay big $$$ for optics that WILL tranmitt UV below 400nm in
wavelength!) The blue glow that you see in mercury tubes is the re-radiations
from the glass itself and they are mostly from the INSIDE surface of the glass
where UV light first hit (a sign that UV light did not go too far through the
glass, otherwise you should see the glow throughout the glass)
hopper
_______________________________________________________________________________
(snip)
3. I'm not sure if you all realise this, but mercury vapour rectifiers
actually give off a lot of invisible UV light. From memory, they give
off a lot of UV type B, which some of you may know is more strongly
correlated to melanoma than UV-A (which does most of the burning and
sunburn, but is not as strongly related to melanoma). This is a
concern. Also this UV predisposes to cataracts, so if any of you guys
love staring into the romantic glow of your 83 mercury vapour rectifiers
sitting in your SE amps, then you may be inadvertently damaging your
eyes. Note that this is a long term effect, and something best avoided.
....
=========================================================================
From: Grego Sanguinetti <grego@latticesemi.com>
Subject: Re: 83s (again)
Date: Mon, 6 Apr 1998 16:33:26 -0700 (PDT)
Source: Sound Digest Archive v01.n246
On Sat, 4 Apr 1998, Robert Ang wrote:
> Sorry to bring up an old topic again, but only today did I get my hot
> little hands on 2 NOS RCA 83 mercury vapour rectifiers. They are US
> Navy 1942 NOS tubes, beautifully made - I'm proud to own them! Anyway,
> the principle reason why I want to use them is because of the
> interesting case reports from the JoeList, that low impedence rectifiers
>
> DO make a difference. However, I have concerns on several problems with
>
> their implication:
>
> 1. How does everyone overcome the problems with radiating RF from the
> rectifier? My friend has used them in the past, but now refuses to use
> them because he says his tuner in the car parked outside actually starts
I have not experienced any problems with them but with other, higher
voltage and larger current MV rectifiers, I have solved B+ supply-borne
RF hash with a choke, say 120-200uH, on each plate.
> 2. Since the valve needs to be preheated, do people normally use a
> timing circuit to turn it on or just have two manual switches for
> separate filament and plate transformers?
have done both manual and delayed. For delayed, I typically use thermal
delay relays followed by an inrush current limitter to ease the B+ ramp.
Also use these on the primary of it's filament transformer to softstart
those big filaments.
> 3. I'm not sure if you all realise this, but mercury vapour rectifiers
> actually give off a lot of invisible UV light. From memory, they give
not an issue, as others posted.
enjoy!
- -grego
=========================================================================
From: Steve Van Osdell <svanos@toast.net>
Subject: 8417 Bias dilemna
Date: Mon, 09 Feb 1998 22:14:48 -0600
Source: Sound Digest Archive v01.n187
I might have found an explanation to my bias problems with my Fisher SA1000
amp using the new 8417's. The new ones I installed or GE's. Now the 8417
was originally an RCA design and was able to handle 750 volts. I have
heard that some other tube makers took some of the best 6L6's, and
relabeled them to 8417's, and that this will work in applications that
aren't fully utilizing the potential of the 8417 like my Fisher.
I might be getting tube runaway with these 'fake' GE 8417's if this is
true. I did notice that the GE's were about 1" shorter than the Fisher
branded 8417's that were original.
Any thoughts? Steve
=========================================================================
From: cgooch@jarl.cs.uop.edu
Subject: 8417 tube quesiotn
Date: Fri, 13 Nov 1998 21:23:24 -0800 (PST)
Source: Sound Digest Archive v01.n490
I just ran across some 8417 tubes that are labeled Bogen for Sylvania....
but the picture of them shows that the top of the tube is not
frosted..they are clear like the GE tube of which I have heard bad things
about.... can anyone clear this up for me?If you need to see a picture
let me know wna I will send you one.... pardon my spelling once again.
Thanks.
Cary
=========================================================================
From: "Robert Ang" <rang@opera.iinet.net.au>
Subject: 845 Amp
Date: Sun, 19 Jul 1998 08:33:11 +0800
Source: Sound Digest Archive v01.n348
Gee, sorry guys. I suffered from the premature push-the-send button on my
mailing program.
Unfortunately I'm having trouble uploading the file (something wrong with
the server), so sit tight and it should be up in the next day.
Sorry for the inconvenience!
Rob.
=========================================================================
From: evaguido <EvaGuido@iaehv.nl>
Subject: Re: 845 Question
Date: Fri, 23 Oct 1998 18:53:20 +0200
Source: Sound Digest Archive v01.n465
Do not worry to much. As long as the inter-plate distances remain as they
are intended, the tube will work fine
Guido
At 09:19 23-10-98 -0500, Jeff Brouwer wrote:
>
> Hi all,
>
> A pair of RCA 845's just arrived in the mail; I noticed that on one of
> the tubes that when it's handled (as in unrolling it from the bubble
> wrap), the plate structure can be felt shifting a bit. Given the huge
> plate assembly I guess this doesn't surprise me, but I'd appreciate
> any advice on whether this is normal or not.
>
> Thanks for the help,
>
> -jeff
>
>
>
>
>
>
=========================================================================
From: "Jeff Brouwer"<jbrouwer@mail.crc.com>
Subject: 845 Question
Date: Fri, 23 Oct 98 09:19:29 -0500
Source: Sound Digest Archive v01.n465
Hi all,
A pair of RCA 845's just arrived in the mail; I noticed that on one of
the tubes that when it's handled (as in unrolling it from the bubble
wrap), the plate structure can be felt shifting a bit. Given the huge
plate assembly I guess this doesn't surprise me, but I'd appreciate
any advice on whether this is normal or not.
Thanks for the help,
-jeff
=========================================================================
From: Kurt Steffensen <solvin-aurum@get2net.dk>
Subject: Re: 845 Question
Date: Fri, 23 Oct 1998 23:46:29 +0200
Source: Sound Digest Archive v01.n466
Jeff Brouwer wrote:
>
> Hi all,
>
> A pair of RCA 845's just arrived in the mail; I noticed that on one of
> the tubes that when it's handled (as in unrolling it from the bubble
> wrap), the plate structure can be felt shifting a bit. Given the huge
> plate assembly I guess this doesn't surprise me, but I'd appreciate
> any advice on whether this is normal or not.
>
> Thanks for the help,
>
> -jeff
>
>
>
Dear Jeff.
I am sorry to have to tell you this, but that 845 is certainly
defective.
I would not put any high voltage on it, if I were you.
The plate structures of any tube is not supposed to move to the extend,
that
it can be observed by the eye or felt in the hand holding it.
Even if it does not sparks, when you put on high voltage,
the characteristics will cycle as mad.(Lots of distortion)
BTW; If you do not know what to do with only one 845, I will be happy to
purchase it. (Or trade against other tubes)
(But that is not the reason, I am bringing you the sad message)
- - Sincerely Kurt Steffensen
- - Sincerely Kurt Steffensen
=========================================================================
From: "Sune Frost-Olsen" <sune@post5.tele.dk>
Subject: 85A2 reg. operating points?
Date: Fri, 1 Jan 1999 12:49:05 +0100
Source: Sound Digest Archive v01.n554
HAPPY NEW YEAR to all!!!
Pls can anybody tell me what voltage the regulator tube 85A2 stabilize at + operating current?
Thanks in advance!
Regards,
Sune
_______________________________________
SFO Denmark
sune@post5.tele.dk
=========================================================================
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Subject: 85% Discount on DeskTop MoneyMachine
Date: Wed, 19 Nov 1997 19:50:57 -0500 (EST)
Source: Sound Digest Archive v01.n115
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