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!)