12AV5GA push pull triode amplifier.

[kodabmx]

I'm running about 320V, 120ma idle per tube...

 

[kodabmx]

In triode mode you have very local feedback, but if you take the feedback to the input stage you linearize both. Without some kind of feedback the plate impedance maybe too high for your OPT.

I use a global feedback loop.

 

[TonyTecson]

I'm running about 320V, 120ma idle per tube...

thanks...

 

[starlite2991]

12AV5GA push pull triode amplifier

Koda
Hello, what are the specs of the output transformer? Also, does the SMPS supply enough power at 320v dc for the output bulbs?
vince@kd7tww.com
73 Vince

 

[pblix]

Nice amp, but the chassis really need a bottom cover for safety.

 

[kodabmx]

The OPT would be 3k:8R... AFAIR this amp only used SMPS for heaters and the VA/PI stage. The output stage used a 120V isolation transformer with a delon doubler circuit for the B+. There is a boost converter that will provide all the DC needed though, I use one in another amp running from an ATX supply.

There was a bottom cover... With it on the picture of the insides doesn't look as good though

This amp has been scrapped. It's chassis was turned into a KT120 amplifier, and then it too was scrapped. The parts are waiting for reuse now.

 

[pblix]

There was a bottom cover... With it on the picture of the insides doesn't look as good though

Looked suspicious with the feet mounted and no additional screw holes...but if you say so...

 

[Lingwendil]

A lot of people run without a cover on the bottom during testing, break in, etc. So long as you understand all the details of your project and environment it's up to you to ensure safety is the priority.

 

[enzoastro]

For reference my old breadboard 12av5 pp with a pair of 6p52 with a CCS under them as drivers managed 1% thd at 8w output zero feedback.
nice tubes!

 

[kodabmx]

Nice indeed I was getting about 15W out of them with 300V and a 3k plate to plate load connected as triodes. No idea the THD though.

 

[enzoastro]

Think mine was 280v into 6k6, so that sounds right ��

 

[kodabmx]

Nice. I was running gNfB, too though. Mild though I think. I'm bad with the math and can't remember the exact numbers, but I think I worked it out to being about 8db...

 

[enzoastro]

Did you like the sound? I didn't get round to building a second channel so it's difficult to tell much other than it didn't sound bad!?
I've got some bigger sweep tubes I might try 6cb5a, I've been drawn away from pp experiments by the simplicity of SE topologies, but have some input step up transformers that should make pp simpler so hopefully I'll get back to them!

 

[kodabmx]

It was a stereo amp. I did like the sound though. Now my daily driver is running 6P36S.

 

[enzoastro]

I've got some of those in stock too, I'll add them to the list!

 

[multi]

How does the EL36 compare to the 6av5 as triode? I have an El36 triode connected amp,
appears from this thread the el36 has more power out put?

 

[TonyTecson]

while you are at it, i would encourage you to try the 6AU5 also.....

 

[kodabmx]

I assume the EL36 (6P31S) would plug in and work if you rewire the sockets.

6AU5 would work, too.

 

[TonyTecson]

no plate caps for the 6au5 just like the 6av5, 6fw5...

compactron equivalent is the 6gv5...

 

[kodabmx]

Or use 25BQ6 and run the heaters in series for a stereo PP amp...