low voltage hybrid power amplifier

[assembled]

Hello everyone, I am looking for a low (in valve standards) voltage hybrid power amplifier. It should be designed to run from +-40V rails or less. Furthermore, should be simple to build. I will suggest it to 10..14 y.old electronics amateurs as a substitute for HV electric shock and similar projects.

If anyone would happen to have a tested design, I would be more than happy to give it a try.

I have found only this project, thus I would prefer something smaller, cheaper and without global feedback. Power of 2..5W is more than enough for valve audio try-out. Headphone amplifiers are not an option.

Thanks and regards,
Paulius

 

[ingenieus]

With hybrid, do you mean tube input stage and solid state output? I have doodled such a thing in Pspice, but without much success so far. Then again, I was looking for 50W or so of output power. If you are only looking for 2-5W, it should be (relatively) easy.

 

[DF96]

Many hybrid circuits combine the worst features of valves and solid-state, not the best (as is often claimed). Low voltage supplies and a fear of feedback make this mistake more likely.

 

[tomlang]

This may be of interest but needs an SE transformer...

http://www.diyaudio.com/forums/tube...-12w-600ohm-4-8-ohm-output-transformer-2.html

 

[ingenieus]

A hybrid could also mean tubes in the signal path and semiconductors in the power supply, I guess.

In any case, this all-tube 30V circuit might be what the OP is looking for:

Sopht amps - all tube 30v amps

 

[Bigun]

I would prefer something smaller, cheaper and without global feedback. Power of 2..5W is more than enough for valve audio try-out. Headphone amplifiers are not an option.

Class A makes a lot of heat, especially simple single ended circuits like the one you linked as they are very inefficient.

I suggest you look to Class AB. Most people will say it needs feedback, but at low power into a reasonable load there are those who find it works adequately. At the end you will have to accept some tradeoffs.

One option is to make a triode cathode follower buffer and put a Chipamp power op-amp after it.

 

[jazbo8]

Vox has been making the VR series geetar amp for years, mod and tweak for your own needs:

An externally hosted image should be here but it was not working when we last tested it.

Jaz

 

[widowmaker]

I can offer to you my last solid state SE amp without global feedback
(more than 5 years old).
Unfortunately I don't have updated circuit diagram here (at work),
so, I'm posting only amplifier part just to have an idea what I'm talking about...
More explanations later (hope can do this tonight).

 

[widowmaker]

Forgot to write that this is not a hybrid amp,
but can be redesigned with tube input stage.

 

[jerluwoo]

An idea I've been kicking around for a bit now. Very simple in how it works and once offset is adjusted no need to mess with it again as the offset only varies about 25mV or so when the tube is warming up. Power supply can be made from two 12-0-12 transformers piggybacked. Tube can be nearly any medium mu type like 6sn7 or 12au7 etc. without any changes.