Back in the late 1950's Popular Electronics Magazine published a
construction article on a push pull triode amplifier that used one of the
Dual Television Triodes like the 6BX7 as the output tube. The amplifier
also used an expensive output transformer whose brand name started with
the letter "P", I think it was a Peerless transformer, but it was a long
time ago and their is a slight possibility it was a Partridge transformer.

Does anyone remember this article an know what year and month it
appeared? I would like to look for a copy of the magazine on eBay. This
article was followed by copycat articles in Audio Magazine and either
Radio & Television News or Radio Electronics, or both, but it is the
original Popular Electronics article I am looking for.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

It would be a Peerless or a Partridge, yup.

John Byrns wrote:
Back in the late 1950's Popular Electronics Magazine published a
construction article on a push pull triode amplifier that used one of the
Dual Television Triodes like the 6BX7 as the output tube. The amplifier
also used an expensive output transformer whose brand name started with
the letter "P", I think it was a Peerless transformer, but it was a long
time ago and their is a slight possibility it was a Partridge transformer.


It would great to read that article but my guess is that it would be
the 6AS7. If you get a copy can you put it up on your web site.


Surf my site: http://www.retrotech.ca

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

" said:


John Byrns wrote:
Back in the late 1950's Popular Electronics Magazine published a
construction article on a push pull triode amplifier that used one of the
Dual Television Triodes like the 6BX7 as the output tube. The amplifier
also used an expensive output transformer whose brand name started with
the letter "P", I think it was a Peerless transformer, but it was a long
time ago and their is a slight possibility it was a Partridge transformer.


It would great to read that article but my guess is that it would be
the 6AS7. If you get a copy can you put it up on your web site.


Nope.
There were several 6BX7 designs published in the late '50s and early
'60s.
One of them was published in 1962 in the Dutch magazine "Radio
Bulletin", which consisted of a push pull stage with 2 6BX7s, each
double triode in parallel.
It was good for about 8...10 watts, depending on the quality of the
output transformer.
I built one in stereo, and it sounds surprisingly good with 2
Lafayette LA244B output transformers, originally designed for use with
2 x EL84 in PP.

If you're interested John, I can scan the schematic and e-mail it to
you, or put it on some place on the web.

--

- Never argue with idiots, they drag you down their level and beat you with experience. -

wrote:
John Byrns wrote:
Back in the late 1950's Popular Electronics Magazine published a
construction article on a push pull triode amplifier that used one of the
Dual Television Triodes like the 6BX7 as the output tube. The amplifier
also used an expensive output transformer whose brand name started with
the letter "P", I think it was a Peerless transformer, but it was a long
time ago and their is a slight possibility it was a Partridge transformer.


It would great to read that article but my guess is that it would be
the 6AS7. If you get a copy can you put it up on your web site.


I have heard 6AS7 amps but it takes too much drive to be a practical
thing. You can use an interstage transformer but you wind up running
open loop due to phase shift, and we know what part of the cow's
anatomy that often sounds like! SOME NFB is needed for cone control in
most cases. I have thought about using a high voltage (substantially
higher than the 6AS7 B+) driver section, but it means using some
unconventional practices. Another idea is to emulate the driver
circuits of the Altec 260B (autoformers) or 1570B (tapped choke), Looks
expensive and i think the 6AS7 is best left to do what it does best,
regulate bench power supplies. It was probably the 6BX7 since 6AS7s
arent found in teevees anyway.

In article , Sander deWaal
wrote:

" said:

John Byrns wrote:
Back in the late 1950's Popular Electronics Magazine published a
construction article on a push pull triode amplifier that used one of the
Dual Television Triodes like the 6BX7 as the output tube. The amplifier
also used an expensive output transformer whose brand name started with
the letter "P", I think it was a Peerless transformer, but it was a long
time ago and their is a slight possibility it was a Partridge transformer.

It would great to read that article but my guess is that it would be
the 6AS7. If you get a copy can you put it up on your web site.

Nope.
There were several 6BX7 designs published in the late '50s and early
'60s.
One of them was published in 1962 in the Dutch magazine "Radio
Bulletin", which consisted of a push pull stage with 2 6BX7s, each
double triode in parallel.
It was good for about 8...10 watts, depending on the quality of the
output transformer.
I built one in stereo, and it sounds surprisingly good with 2
Lafayette LA244B output transformers, originally designed for use with
2 x EL84 in PP.

If you're interested John, I can scan the schematic and e-mail it to
you, or put it on some place on the web.


Hi Sander,

While it's the Popular Electronics article I am especially interested in
locating, as I think it was the first such design at least on this side of
the pond, I would be interested in seeing the Dutch take on this idea if
you would be so kind as to place it somewhere on the web, or email it to
me. The Popular Electronics version predated stereo and used only a
single dual triode, a 6BX7 IIRC, in the output stage to give 4 or 5 Watts
output. It was a very compact design featuring a high quality output
transformer.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

(John Byrns) said:

Hi Sander,

While it's the Popular Electronics article I am especially interested in
locating, as I think it was the first such design at least on this side of
the pond, I would be interested in seeing the Dutch take on this idea if
you would be so kind as to place it somewhere on the web, or email it to
me. The Popular Electronics version predated stereo and used only a
single dual triode, a 6BX7 IIRC, in the output stage to give 4 or 5 Watts
output. It was a very compact design featuring a high quality output
transformer.


Hi John,

For your benefit (and that of others), I posted following 3 pages,
containing the schematics and a description of this amplifier, to
imageshack:

http://img375.imageshack.us/img375/3889/file00155ic.jpg
http://img375.imageshack.us/img375/618/file00168dt.jpg
http://img375.imageshack.us/img375/4465/file00179ut.jpg

Get someone to translate it for you :-)

The amp I once built, used a different driver arrangement with one
6SN7GTB per channel, but the power stage was pretty much the same.

I still use this amp in my workplace system, to my utmost
satisfaction.

--

- Never argue with idiots, they drag you down their level and beat you with experience. -

Bret Ludwig wrote:

wrote:
John Byrns wrote:
Back in the late 1950's Popular Electronics Magazine published a
construction article on a push pull triode amplifier that used one of the
Dual Television Triodes like the 6BX7 as the output tube. The amplifier
also used an expensive output transformer whose brand name started with
the letter "P", I think it was a Peerless transformer, but it was a long
time ago and their is a slight possibility it was a Partridge transformer.


It would great to read that article but my guess is that it would be
the 6AS7. If you get a copy can you put it up on your web site.


I have heard 6AS7 amps but it takes too much drive to be a practical
thing. You can use an interstage transformer but you wind up running
open loop due to phase shift, and we know what part of the cow's
anatomy that often sounds like! SOME NFB is needed for cone control in
most cases. I have thought about using a high voltage (substantially
higher than the 6AS7 B+) driver section, but it means using some
unconventional practices. Another idea is to emulate the driver
circuits of the Altec 260B (autoformers) or 1570B (tapped choke), Looks
expensive and i think the 6AS7 is best left to do what it does best,
regulate bench power supplies. It was probably the 6BX7 since 6AS7s
arent found in teevees anyway.

If you had paid some attention you would have seen a circuit here on the iNet a
while ago. It was published in both the Excited States of America & the Kingdom of
UK a few years ago, solving that problem! It uses boot strapping. Very simple. And
no HV driver to kill someone. Even you could understand it! (Well, maybe)

John Stewart

Hi,

John Byrns wrote:
Back in the late 1950's Popular Electronics Magazine published a
construction article on a push pull triode amplifier that used one of the
Dual Television Triodes like the 6BX7 as the output tube. The amplifier

Electronics World published a 6BX7 design in October 1960, by Blum,
which used a Dynaco A-410 15W potted transformer. I built one, and a
stereo version which I'm still using as my main amplifier. Blum based
his design on an article "Small Fi" by Paul Popenoe Jr. in the 1957
"Hi-Fi Guide and Yearbook." I also found another reference by Becker
in Radio-Electronics for February 1957, an article titled "TV Tube For
High Fidelity" (p.39).

I'm not aware of any Pop'tronics article but as I didn't start
subscribing until about 1960 I may have missed it. However I have all
the issues now and I think I would have made a note if I had run
across a 6BX7 design.

Alan

In article , Sander deWaal
wrote:

(John Byrns) said:

Hi Sander,

While it's the Popular Electronics article I am especially interested in
locating, as I think it was the first such design at least on this side of
the pond, I would be interested in seeing the Dutch take on this idea if
you would be so kind as to place it somewhere on the web, or email it to
me. The Popular Electronics version predated stereo and used only a
single dual triode, a 6BX7 IIRC, in the output stage to give 4 or 5 Watts
output. It was a very compact design featuring a high quality output
transformer.


Hi John,

For your benefit (and that of others), I posted following 3 pages,
containing the schematics and a description of this amplifier, to
imageshack:

http://img375.imageshack.us/img375/3889/file00155ic.jpg
http://img375.imageshack.us/img375/618/file00168dt.jpg
http://img375.imageshack.us/img375/4465/file00179ut.jpg

Get someone to translate it for you :-)

The amp I once built, used a different driver arrangement with one
6SN7GTB per channel, but the power stage was pretty much the same.

I still use this amp in my workplace system, to my utmost
satisfaction.


Hi Sander,

Thanks for posting the Dutch article, it even includes a short
bibliography listing the Radio-Electronics and Audio magazine articles,
which eliminated the need for me to hunt through my collection. I was
able to directly pull the Radio-Electronics article off the shelf, but
sadly I found that I didn't have the relevant issue of Audio magazine,
which I thought I had.

This Dutch version is an interesting variation in that it uses a long
tailed pair as a phase splitter, IIRC the Popular Electronics version used
a split load, or concertina type of phase splitter, as does the
Radio-Electronics version. The Dutch article doesn't seem to give any
specifics beyond the part number on the output transformer used, I was
curious what plate to plate load impedance they choose, what plate to
plate load did you use in the one you built?

I will have to keep hunting for the date of the Popular Electronics
article, I was guessing some time in the first part of 1957, if that is
correct then the Radio-Electronics article may have been the first as it
was published in February of 1957. An older friend built one at the time
and I remember the expensive output transformer that was specified in the
Popular Electronics article.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

In article , Alan Douglas
adouglasatgis.net wrote:

Hi,

John Byrns wrote:
Back in the late 1950's Popular Electronics Magazine published a
construction article on a push pull triode amplifier that used one
of the
Dual Television Triodes like the 6BX7 as the output tube. The amplifier

Electronics World published a 6BX7 design in October 1960, by Blum,
which used a Dynaco A-410 15W potted transformer. I built one, and a
stereo version which I'm still using as my main amplifier. Blum based
his design on an article "Small Fi" by Paul Popenoe Jr. in the 1957
"Hi-Fi Guide and Yearbook." I also found another reference by Becker
in Radio-Electronics for February 1957, an article titled "TV Tube For
High Fidelity" (p.39).

I'm not aware of any Pop'tronics article but as I didn't start
subscribing until about 1960 I may have missed it. However I have all
the issues now and I think I would have made a note if I had run
across a 6BX7 design.

Alan


Hi Alan,

Thanks for posting the reference to the Electronics World article, as I
think I mentioned in an earlier post, I thought there may have also been
an article in Radio & Television News/Electronics World, I should have
that one in deep storage and I will have to dig it out.

The "Small Fi" name sounds very familiar, I wonder if that could be the
article I am thinking of which I thought was in Popular Electronics
sometime around 1957. What does the "Small Fi" amplifier look like? A
friend built a 6BX7 monoblock amplifier sometime around 1957 exactly as it
was described in an article which I have always remembered as coming from
Popular Electronics, but perhaps my memory has faded somewhat. What does
the "Small Fi" amplifier look like? The one I am thinking of was a very
compact monoblock amplifier using three tubes with a single 6BX7 as a push
pull output stage, and a very expensive output transformer which IIRC was
a Peerless model, although there is a slight chance it was a Partridge
transformer.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

"John Byrns" wrote in message
...
: In article , Sander deWaal
: wrote:
:
: (John Byrns) said:
:
: Hi Sander,
:
: While it's the Popular Electronics article I am especially interested in
: locating, as I think it was the first such design at least on this side of
: the pond, I would be interested in seeing the Dutch take on this idea if
: you would be so kind as to place it somewhere on the web, or email it to
: me. The Popular Electronics version predated stereo and used only a
: single dual triode, a 6BX7 IIRC, in the output stage to give 4 or 5 Watts
: output. It was a very compact design featuring a high quality output
: transformer.
:
:
: Hi John,
:
: For your benefit (and that of others), I posted following 3 pages,
: containing the schematics and a description of this amplifier, to
: imageshack:
:
: http://img375.imageshack.us/img375/3889/file00155ic.jpg
: http://img375.imageshack.us/img375/618/file00168dt.jpg
: http://img375.imageshack.us/img375/4465/file00179ut.jpg
:
: Get someone to translate it for you :-)
:
: The amp I once built, used a different driver arrangement with one
: 6SN7GTB per channel, but the power stage was pretty much the same.
:
: I still use this amp in my workplace system, to my utmost
: satisfaction.
:
:
: Hi Sander,
:
: Thanks for posting the Dutch article, it even includes a short
: bibliography listing the Radio-Electronics and Audio magazine articles,
: which eliminated the need for me to hunt through my collection. I was
: able to directly pull the Radio-Electronics article off the shelf, but
: sadly I found that I didn't have the relevant issue of Audio magazine,
: which I thought I had.
:
: This Dutch version is an interesting variation in that it uses a long
: tailed pair as a phase splitter, IIRC the Popular Electronics version used
: a split load, or concertina type of phase splitter, as does the
: Radio-Electronics version. The Dutch article doesn't seem to give any
: specifics beyond the part number on the output transformer used, I was
: curious what plate to plate load impedance they choose, what plate to
: plate load did you use in the one you built?
:
: I will have to keep hunting for the date of the Popular Electronics
: article, I was guessing some time in the first part of 1957, if that is
: correct then the Radio-Electronics article may have been the first as it
: was published in February of 1957. An older friend built one at the time
: and I remember the expensive output transformer that was specified in the
: Popular Electronics article.
:
:
: Regards,
:
: John Byrns

Triode Dick mentions the Amroh U70BN, using it in an EL84 pp amp.
A typical EL84 PP would have Raa=8 K.

http://www.circuitsonline.net/forum/view/24038
gives a schematic using a Lafayette 7K::8 Ohms pp tranny for
a 6BX7 pp amp.

6K5..10K Raa seems fine, total Rp is only 1K3.
Some points you may have missed, the article being in Dutch and all:

the author recommends 4 separate adjustable cathode resistors

he compares the powerstage efficiency of EL84pp and this BX7pp,
and they are comparable at 50% (excl. filament heating)

cheers,
Rudy

(John Byrns) said:

This Dutch version is an interesting variation in that it uses a long
tailed pair as a phase splitter, IIRC the Popular Electronics version used
a split load, or concertina type of phase splitter, as does the
Radio-Electronics version. The Dutch article doesn't seem to give any
specifics beyond the part number on the output transformer used, I was
curious what plate to plate load impedance they choose, what plate to
plate load did you use in the one you built?


Hi John,

I used salvaged trannies from a Lafayette/Bocama LA244B, which used 2
EL84s in PP.
The R-aa is 8 kohms, which, according to my calculations, is just
above the right Ra-a for 2 x 6BX7.

Nevertheless, the amp sounds splendid with it.
The transformer, mentioned in the article, is an Amroh U72B, which was
intended for 2 EL84s in PP as well.
The Amroh transformers are better than the Lafayettes in terms of
stray capacitance and leakage induction, that's why they are well
sought after here in Holland.

In my amp, I used separate cathode resistors of 1 kohm/5 watt with
bypass caps of 220 uF/100V.
This was necessary because of the tubes not being matched.

The driver stage was a 6SN7 cathodyne or concertina phase splitter,
which provides enough drive for the 6BX7's grids when supplied with a
higher voltage, derived from a voltage doubler at the transformer.

--

- Never argue with idiots, they drag you down their level and beat you with experience. -

"Ruud Broens" said:

http://www.circuitsonline.net/forum/view/24038
gives a schematic using a Lafayette 7K::8 Ohms pp tranny for
a 6BX7 pp amp.


That's my amp allright, with 2 omissions:
The voltage doubler for the driver stage isn't in there, and
the grid stoppers belong between the grid grounding resistors and the
grids, not before.
I mentioned that later in the thread.

--

- Never argue with idiots, they drag you down their level and beat you with experience. -

"Sander deWaal" notorious audio pro employee;-)congrats wrote in message
...
: (John Byrns) said:
:
: This Dutch version is an interesting variation in that it uses a long
: tailed pair as a phase splitter, IIRC the Popular Electronics version used
: a split load, or concertina type of phase splitter, as does the
: Radio-Electronics version. The Dutch article doesn't seem to give any
: specifics beyond the part number on the output transformer used, I was
: curious what plate to plate load impedance they choose, what plate to
: plate load did you use in the one you built?
:
:
: Hi John,
:
: I used salvaged trannies from a Lafayette/Bocama LA244B, which used 2
: EL84s in PP.
: The R-aa is 8 kohms, which, according to my calculations, is just
: above the right Ra-a for 2 x 6BX7.
:
: Nevertheless, the amp sounds splendid with it.
: The transformer, mentioned in the article, is an Amroh U72B, which was
: intended for 2 EL84s in PP as well.
: The Amroh transformers are better than the Lafayettes in terms of
: stray capacitance and leakage induction, that's why they are well
: sought after here in Holland.
:
: In my amp, I used separate cathode resistors of 1 kohm/5 watt with
: bypass caps of 220 uF/100V.
: This was necessary because of the tubes not being matched.
:
: The driver stage was a 6SN7 cathodyne or concertina phase splitter,
: which provides enough drive for the 6BX7's grids when supplied with a
: higher voltage, derived from a voltage doubler at the transformer.
:
: --

any ideas why the pp is not realized with both halves of each tube
in pp ? Seems you get a better change of the tubes 'staying together'
with aging, that way.

R.

"Ruud Broens" said:


"Sander deWaal" notorious audio pro employee;-)congrats wrote in message


Zeg, heb jij Circuits Online doorgespit of zo?
Ik heb het toch redelijk stil gehouden hier.......

Maar 't is een wereldjob, helemaal naar mijn zin! :-)


any ideas why the pp is not realized with both halves of each tube
in pp ? Seems you get a better change of the tubes 'staying together'
with aging, that way.


I don't think it works that way, this is not just like a double
transistor with the 2 elements on 1 die.

Maybe you're right though, but then I'll have to rewire the entire
power stage again.......

--

- Never argue with idiots, they drag you down their level and beat you with experience. -

"Sander deWaal" wrote in message
...
: "Ruud Broens" said:
:
:
: "Sander deWaal" notorious audio pro employee;-)congrats wrote in message
:
:
: Zeg, heb jij Circuits Online doorgespit of zo?
: Ik heb het toch redelijk stil gehouden hier.......
:
: Maar 't is een wereldjob, helemaal naar mijn zin! :-)
:
:
heel fijns !

hehe, nope, just from what was available on rao:
: : As of feb. 2006, I'll be working for an audio company.
: : Does that change my "authority" on RAO or RATubes?
and googling for the Amroh U70BN, as mentioned in the Kosterman article :-)

: any ideas why the pp is not realized with both halves of each tube
: in pp ? Seems you get a better change of the tubes 'staying together'
: with aging, that way.
:
:
: I don't think it works that way, this is not just like a double
: transistor with the 2 elements on 1 die.

psst, don't wake up Graham ;-)
it was an educated guess, in that the cathode formulation in one
envelope are certainly from the same batch, applied at the same
time of production..
:
: Maybe you're right though, but then I'll have to rewire the entire
: power stage again.......
:
yep, wiring would be one reason not to do _that_

fine thread, this
Rudy

"Ruud Broens" said:


: any ideas why the pp is not realized with both halves of each tube
: in pp ? Seems you get a better change of the tubes 'staying together'
: with aging, that way.


: I don't think it works that way, this is not just like a double
: transistor with the 2 elements on 1 die.


psst, don't wake up Graham ;-)
it was an educated guess, in that the cathode formulation in one
envelope are certainly from the same batch, applied at the same
time of production..


AFAIK, the elements within the tube were pre-fabricated before
assembly of the entire electrode structure took place.
E.g. the cathode tubes themselves could be from different batches
(remember this is a indirectly heated tube).
I've seen pictures of how this was done in the old days: some guy (or
girl!) spray-painting endless rows of cathode tubes, of which lateron
the appropriate lengths were cut for all kinds of tubes.

Therefore, I don't think that the "same batch" idea has any merit wrt.
matched halves of a tube.

--

- Never argue with idiots, they drag you down their level and beat you with experience. -

"Sander deWaal" wrote in message
...
: "Ruud Broens" said:
:
:
: : any ideas why the pp is not realized with both halves of each tube
: : in pp ? Seems you get a better change of the tubes 'staying together'
: : with aging, that way.
:
:
: : I don't think it works that way, this is not just like a double
: : transistor with the 2 elements on 1 die.
:
:
: psst, don't wake up Graham ;-)
: it was an educated guess, in that the cathode formulation in one
: envelope are certainly from the same batch, applied at the same
: time of production..
:
:
: AFAIK, the elements within the tube were pre-fabricated before
: assembly of the entire electrode structure took place.
: E.g. the cathode tubes themselves could be from different batches
: (remember this is a indirectly heated tube).
: I've seen pictures of how this was done in the old days: some guy (or
: girl!) spray-painting endless rows of cathode tubes, of which lateron
: the appropriate lengths were cut for all kinds of tubes.
:
: Therefore, I don't think that the "same batch" idea has any merit wrt.
: matched halves of a tube.
:
: --

err, you're write :-)
otoh, occam's razor and all that, same~same more likely

chinese proverb,
Rudy

The Popular Electronics version predated stereo and used only a
single dual triode, a 6BX7 IIRC, in the output stage to give 4 or 5
Watts
output.

I made an amp with paralleled PP 6BX7, and it sounded great except I
could never get any 6BX7 with matched halves, so I deconstructed it.
I'll probably put 6CK4s in there instead. The two halves are usually
all over the place, which is a problem in need of a solution. Maybe a
CCS underneath, or fixed bias to each half and double the coupling
caps. I tried the latter, but it was just too complex running 8
different bias pots.