Hello All,

I was wondering if someone had any experience building a small SE
amp using a 815 tube. I have a good one laying around and was thinking
how nice this would be. Would driving one using a 12AX7 be possible?

Thanks in advance,
Phil

815... isn't that a twin beam power tube?

so it would be push/pull... no?

sorry for asking more questions and not answering any...

Arv


"Phil" wrote in message
om...
Hello All,

I was wondering if someone had any experience building a small SE
amp using a 815 tube. I have a good one laying around and was thinking
how nice this would be. Would driving one using a 12AX7 be possible?

Thanks in advance,
Phil

(Phil) wrote in message . com...
Hello All,

I was wondering if someone had any experience building a small SE
amp using a 815 tube. I have a good one laying around and was thinking
how nice this would be. Would driving one using a 12AX7 be possible?

It would be possible but dumb. If you must build a single ended amp, a
twin tetrode would be a poor choice. I'm sure someone will trade you
for a 6L6 or EL34 if you want a beam power tube. If you want to use
the 815 for audio there should be curves and some instructions in a
transmitting tube manual. Probably it would be treated like a pair of
6V6's with some common elements, like the 829B and 832.

(Sam Byrams) wrote in message om...
(Phil) wrote in message . com...
Hello All,

I was wondering if someone had any experience building a small SE
amp using a 815 tube. I have a good one laying around and was thinking
how nice this would be. Would driving one using a 12AX7 be possible?

It would be possible but dumb. If you must build a single ended amp, a
twin tetrode would be a poor choice. I'm sure someone will trade you
for a 6L6 or EL34 if you want a beam power tube. If you want to use
the 815 for audio there should be curves and some instructions in a
transmitting tube manual. Probably it would be treated like a pair of
6V6's with some common elements, like the 829B and 832.

"Dumb"? I'm curious as to why "dumb"? I presume you're referring to
some inherent technical drawback to paralleling beam power tubes that
I'm not aware of (in class A audio applications)?

Or maybe it's the common filament, where you'd really need a DC supply
because you'd never get the typical AC filament SE hum out of it....?
(don't know, haven't tried here.) Or maybe you were just being rude,
or inconsiderate, or hadn't thought of it first?

A trade for a generic 6L6/EL34 would be a bad deal from a business
standpoint (the 815 is worth a bit more.) However, the current street
price for a RCA NOS 815 isn't unreasonable (i.e. AES) so setting a few
spares aside isn't out of the question (it is one tube I doubt anybody
will ever attempt to re-issue.)

I've a few NOS 815s myself, and have periodically thought how
cute/cool a push pull amp would be using one for the output (but then
again I don't like the overload characteristics of a SE amp for
guitar, and want more bang -watts- for my buck.)

The 815, 829B, and 832) are in the RCA Transmitting Tubes manual TT-4
(1956) and I quote the following (specs for AF push pull AB
application, when given):

815 829B 832
Static Plate Dissipation (per section) 20 30 (~10)*
Plate to Plate Load Resistance (AB2) 6.2K/8K** 13.75K DNX

*modulation factor 1.0 for CCS rated Class C Telephony
** first figure CCS rating at 400 volts plate, 2nd ICAS rating at 500
volts

In fact there's pretty complete spec stuff on the 815 there, it was
evidently intended for AF amp applications (as opposed to the 832,
where no audio application stuff is mentioned.)

So by the specs IMO a 815 would likely set up similiar to a pair of
6L6GBs (w/ slightly higher plate load). If you persue this, please let
us know how it turns out!
(I've always thought one with two Johnson ceramic plate caps would
look really cool sitting in the middle of a little one-off chassis...)

Cheers,
-Robert
QTS
http://www.Braught.com
real email addy: (remove NoSpam to reply:
Duh!)

I guess that was what I was thinking in that you could probably set it up as
push/pull with one tube...

Arv...

I wonder if I have any of those kicking around


"Robert M. Braught" wrote in message
om...
(Sam Byrams) wrote in message
om...
(Phil) wrote in message
. com...
Hello All,

I was wondering if someone had any experience building a small SE
amp using a 815 tube. I have a good one laying around and was thinking
how nice this would be. Would driving one using a 12AX7 be possible?

It would be possible but dumb. If you must build a single ended amp, a
twin tetrode would be a poor choice. I'm sure someone will trade you
for a 6L6 or EL34 if you want a beam power tube. If you want to use
the 815 for audio there should be curves and some instructions in a
transmitting tube manual. Probably it would be treated like a pair of
6V6's with some common elements, like the 829B and 832.

"Dumb"? I'm curious as to why "dumb"? I presume you're referring to
some inherent technical drawback to paralleling beam power tubes that
I'm not aware of (in class A audio applications)?

Or maybe it's the common filament, where you'd really need a DC supply
because you'd never get the typical AC filament SE hum out of it....?
(don't know, haven't tried here.) Or maybe you were just being rude,
or inconsiderate, or hadn't thought of it first?

A trade for a generic 6L6/EL34 would be a bad deal from a business
standpoint (the 815 is worth a bit more.) However, the current street
price for a RCA NOS 815 isn't unreasonable (i.e. AES) so setting a few
spares aside isn't out of the question (it is one tube I doubt anybody
will ever attempt to re-issue.)

I've a few NOS 815s myself, and have periodically thought how
cute/cool a push pull amp would be using one for the output (but then
again I don't like the overload characteristics of a SE amp for
guitar, and want more bang -watts- for my buck.)

The 815, 829B, and 832) are in the RCA Transmitting Tubes manual TT-4
(1956) and I quote the following (specs for AF push pull AB
application, when given):

815 829B 832
Static Plate Dissipation (per section) 20 30 (~10)*
Plate to Plate Load Resistance (AB2) 6.2K/8K** 13.75K DNX

*modulation factor 1.0 for CCS rated Class C Telephony
** first figure CCS rating at 400 volts plate, 2nd ICAS rating at 500
volts

In fact there's pretty complete spec stuff on the 815 there, it was
evidently intended for AF amp applications (as opposed to the 832,
where no audio application stuff is mentioned.)

So by the specs IMO a 815 would likely set up similiar to a pair of
6L6GBs (w/ slightly higher plate load). If you persue this, please let
us know how it turns out!
(I've always thought one with two Johnson ceramic plate caps would
look really cool sitting in the middle of a little one-off chassis...)

Cheers,
-Robert
QTS
http://www.Braught.com
real email addy: (remove NoSpam to reply:
Duh!)

"bigdaddy" wrote in message
.. .
I guess that was what I was thinking in that you could probably set it up
as
push/pull with one tube...

Arv...

I wonder if I have any of those kicking around


Self-split, PP with triodes is done. That's what Gary Gerhart did with the
Gilmore Jr. I think audiophiles like it. One preamp tube, one power tube.
Could even be the same tube type if you could figure out the mojo. I don't
see why you couldn't do it with a pentode or whatever the 815 is.

(Robert M. Braught) wrote in message . com...
(Sam Byrams) wrote in message om...
(Phil) wrote in message . com...
Hello All,

I was wondering if someone had any experience building a small SE
amp using a 815 tube. I have a good one laying around and was thinking
how nice this would be. Would driving one using a 12AX7 be possible?

It would be possible but dumb. If you must build a single ended amp, a
twin tetrode would be a poor choice. I'm sure someone will trade you
for a 6L6 or EL34 if you want a beam power tube. If you want to use
the 815 for audio there should be curves and some instructions in a
transmitting tube manual. Probably it would be treated like a pair of
6V6's with some common elements, like the 829B and 832.

"Dumb"? I'm curious as to why "dumb"? I presume you're referring to
some inherent technical drawback to paralleling beam power tubes that
I'm not aware of (in class A audio applications)?

Or maybe it's the common filament, where you'd really need a DC supply
because you'd never get the typical AC filament SE hum out of it....?
(don't know, haven't tried here.) Or maybe you were just being rude,
or inconsiderate, or hadn't thought of it first?

A trade for a generic 6L6/EL34 would be a bad deal from a business
standpoint (the 815 is worth a bit more.) However, the current street
price for a RCA NOS 815 isn't unreasonable (i.e. AES) so setting a few
spares aside isn't out of the question (it is one tube I doubt anybody
will ever attempt to re-issue.)

I've a few NOS 815s myself, and have periodically thought how
cute/cool a push pull amp would be using one for the output (but then
again I don't like the overload characteristics of a SE amp for
guitar, and want more bang -watts- for my buck.)

The 815, 829B, and 832) are in the RCA Transmitting Tubes manual TT-4
(1956) and I quote the following (specs for AF push pull AB
application, when given):

815 829B 832
Static Plate Dissipation (per section) 20 30 (~10)*
Plate to Plate Load Resistance (AB2) 6.2K/8K** 13.75K DNX

*modulation factor 1.0 for CCS rated Class C Telephony
** first figure CCS rating at 400 volts plate, 2nd ICAS rating at 500
volts

In fact there's pretty complete spec stuff on the 815 there, it was
evidently intended for AF amp applications (as opposed to the 832,
where no audio application stuff is mentioned.)

So by the specs IMO a 815 would likely set up similiar to a pair of
6L6GBs (w/ slightly higher plate load). If you persue this, please let
us know how it turns out!
(I've always thought one with two Johnson ceramic plate caps would
look really cool sitting in the middle of a little one-off chassis...)

Cheers,
-Robert
QTS
http://www.Braught.com
real email addy: (remove NoSpam to reply:
Duh!)

Thanks for all the info guys. It seems like this would be a bit
complicated to do. As Robert pointed out though, it would be really
cool to have an audio amp using one of these!

Phil

Is that the one that was in the SG systems amps?


On 12 Jul 2004 12:15:19 -0700, (Phil) wrote:

(Robert M. Braught) wrote in message . com...
(Sam Byrams) wrote in message om...
(Phil) wrote in message . com...
Hello All,

I was wondering if someone had any experience building a small SE
amp using a 815 tube. I have a good one laying around and was thinking
how nice this would be. Would driving one using a 12AX7 be possible?

It would be possible but dumb. If you must build a single ended amp, a
twin tetrode would be a poor choice. I'm sure someone will trade you
for a 6L6 or EL34 if you want a beam power tube. If you want to use
the 815 for audio there should be curves and some instructions in a
transmitting tube manual. Probably it would be treated like a pair of
6V6's with some common elements, like the 829B and 832.

"Dumb"? I'm curious as to why "dumb"? I presume you're referring to
some inherent technical drawback to paralleling beam power tubes that
I'm not aware of (in class A audio applications)?

Or maybe it's the common filament, where you'd really need a DC supply
because you'd never get the typical AC filament SE hum out of it....?
(don't know, haven't tried here.) Or maybe you were just being rude,
or inconsiderate, or hadn't thought of it first?

A trade for a generic 6L6/EL34 would be a bad deal from a business
standpoint (the 815 is worth a bit more.) However, the current street
price for a RCA NOS 815 isn't unreasonable (i.e. AES) so setting a few
spares aside isn't out of the question (it is one tube I doubt anybody
will ever attempt to re-issue.)

I've a few NOS 815s myself, and have periodically thought how
cute/cool a push pull amp would be using one for the output (but then
again I don't like the overload characteristics of a SE amp for
guitar, and want more bang -watts- for my buck.)

The 815, 829B, and 832) are in the RCA Transmitting Tubes manual TT-4
(1956) and I quote the following (specs for AF push pull AB
application, when given):

815 829B 832
Static Plate Dissipation (per section) 20 30 (~10)*
Plate to Plate Load Resistance (AB2) 6.2K/8K** 13.75K DNX

*modulation factor 1.0 for CCS rated Class C Telephony
** first figure CCS rating at 400 volts plate, 2nd ICAS rating at 500
volts

In fact there's pretty complete spec stuff on the 815 there, it was
evidently intended for AF amp applications (as opposed to the 832,
where no audio application stuff is mentioned.)

So by the specs IMO a 815 would likely set up similiar to a pair of
6L6GBs (w/ slightly higher plate load). If you persue this, please let
us know how it turns out!
(I've always thought one with two Johnson ceramic plate caps would
look really cool sitting in the middle of a little one-off chassis...)

Cheers,
-Robert
QTS
http://www.Braught.com
real email addy: (remove NoSpam to reply:
Duh!)

Thanks for all the info guys. It seems like this would be a bit
complicated to do. As Robert pointed out though, it would be really
cool to have an audio amp using one of these!

Phil

I've a few NOS 815s myself, and have periodically thought how
cute/cool a push pull amp would be using one for the output (but then
again I don't like the overload characteristics of a SE amp for
guitar, and want more bang -watts- for my buck.)


I'm interested why you don't like the overload characteristic of SE class a
for guitar. How would you describe the sound? I made a 60 watt SE Class and
and quite like the tone, I have an attenuator though at 15 wattts output. I
think the sound is not too modern though. I used a T-1000 triode.

Geoff C wrote in message . ..

I've a few NOS 815s myself, and have periodically thought how
cute/cool a push pull amp would be using one for the output (but then
again I don't like the overload characteristics of a SE amp for
guitar, and want more bang -watts- for my buck.)


I'm interested why you don't like the overload characteristic of SE class a
for guitar. How would you describe the sound? I made a 60 watt SE Class and
and quite like the tone, I have an attenuator though at 15 wattts output.

Hi Geoff,

Ah jeez, I slipped and let one of my opinions out!
;-)

I guess I prefer symetrical to asymetrical clipping (one
over-simplified way of describing typical SE vs. push-pull amp
clipping), I'd call it (subjectively) 'softer', or 'rounder'; also,
bass definition remains intact. SE output amp clipping is more like
preamp stage clipping, which of course is 'fine' too, just different,
a matter of taste (plenty of people like little SE guitar amp designs,
i.e. Univalves, Fender Champs etc.)

I
think the sound is not too modern though. I used a T-1000 triode.

!
Not modern? Like before Class B was invented? ;-)

Your SE T-1000 must be a joy to behold(!); no doubt there's plenty of
low end available for a little EQ boost to recover when clipped...
plus depending on your output tranny wind (and the freq response of
your speaker(s)) maybe some of the excessive 'bite' (IMO) when an SE
amp is clipped isn't there...

But as an 'Efficiency Cop' I'd arrest you for throwing away hundreds
of watts for just a few! ;-)

-Robert
"Respects those who use T-1000s instead of space heaters to keep
warm."

QTS
http://www.Braught.com
real email addy : (remove NoSpam to reply :
Duh!)

Sam Byrams wrote:
(Phil) wrote in message . com...

Hello All,

I was wondering if someone had any experience building a small SE
amp using a 815 tube. I have a good one laying around and was thinking
how nice this would be. Would driving one using a 12AX7 be possible?


It would be possible but dumb. If you must build a single ended amp, a
twin tetrode would be a poor choice.

Maybe use one of the tetrodes for the left channel, and the other
for the right channel. But unless you happen to have a few of these
in your spare tube drawer, it may be an expensive way to go for
the power output and quality of sound you'd get.

(Robert M. Braught) wrote in
om:

Ah jeez, I slipped and let one of my opinions out!
;-)

I guess I prefer symetrical to asymetrical clipping (one
over-simplified way of describing typical SE vs. push-pull amp
clipping), I'd call it (subjectively) 'softer', or 'rounder'; also,
bass definition remains intact. SE output amp clipping is more like
preamp stage clipping, which of course is 'fine' too, just different,
a matter of taste (plenty of people like little SE guitar amp designs,
i.e. Univalves, Fender Champs etc.)

I
think the sound is not too modern though. I used a T-1000 triode.

!
Not modern? Like before Class B was invented? ;-)

Your SE T-1000 must be a joy to behold(!); no doubt there's plenty of
low end available for a little EQ boost to recover when clipped...
plus depending on your output tranny wind (and the freq response of
your speaker(s)) maybe some of the excessive 'bite' (IMO) when an SE
amp is clipped isn't there...

But as an 'Efficiency Cop' I'd arrest you for throwing away hundreds
of watts for just a few! ;-)

-Robert
"Respects those who use T-1000s instead of space heaters to keep
warm."

Well Robert, that is clear what you mean. I don't have strong opinions
any more on whether class A or symmetrical outputs etc. are inherently
better. As you no doubt know, the pre and post equalisation is hugely
important also. I love the sound of Brian May's Vox's but I reckon other
amps could do similar if you try. What I mean by modern is the heavy
bottom of many rock bands these days which I usually suppress to avoid
fuzzy sounds.

You are right that the T-1000 is great for the bass if I crank that up
too. My transformer has a 40 Hz to 30Khz response, is an air gapped c-
core and has pri-sec interleaving. After winding I discovered that I
should not have interleaved because the high end roll off is needed in a
guitar application so I simply placed a small cap across the primary to
achieve the same thing. Yes the amp looks fantastic, the tube is at the
front with a stainless steel reflector and pyrex hand bent window so you
can see it. The speakers are in a separate box and are a pair of richard
Alan British twin cone speakers from the 70's which I had lying around
and because they sound good, I kept them. The amp weighs 32kg and I made
it purely for a bit of fun because I could get the parts free.It is class
A simply because that is the only way to do it with one tube. As for the
efficiency, yes no argument- 450 watts in (inc filament) and 60 out. And
the graphite plate can be seen glowing red in a darkened room. The light
form the filament alone is enough to illuminate the rom. Looks really
cool. I have a spare 3-1000H and a similar EEV one also.