"Output Transfo + FETs" Amplifier

[GlidingDutchman]

From this thread:

http://www.diyaudio.com/forums/showt...28#post1795228

I thought I start a new thread on "SS Amplifier using Output Transformer" based on this readings:

http://www.susan-parker.co.uk/zeus.htm
http://www.susan-parker.co.uk/zeus-construction.htm

Maybe I am chasing ghosts but I think it is worth a bit of discussion.

Basic circuit idea:

SS output devices into a low impedance OPT
Driver stage 6922 or 6H30Pi or something suitable
Tube phase splitter stage
100 watts per channel

[foo]

The only drawback is the price and limited bandwidth of a good output trans.

[dsavitsk]

A little different setup, and way lower power, but conceptually similar.

Differential TDA1543 based NOS DAC

[GlidingDutchman]

Originally posted by foo
The only drawback is the price and limited bandwidth of a good output trans.

I have OPTs...

[guytou]

and the NEMESIS too , from the audiophile french review , a single K135/OPT design .

[Andre Visser]

Now why would you want to ruin the sound of mosfets with a transformer?

[Miles Prower]

Originally posted by Andre Visser
Now why would you want to ruin the sound of mosfets with a transformer?

He's not. He's trying to fix that. The SEPP output that uses complimentary N-Channel / P-Channel pairs pretty much SUX. It works just fine with BJTs, but BJT complementary NPN / PNP pairs are a good deal more complementary than MOSFETs. Stick with N-Channel or P-Channel devices, but not both in the same circuit. I've never heard one of these that didn't sound, more or less, "off". Of course, the "Big Box" manufacturers like that because no OPT is cheaper than the cheapest OPT. And a really good OPT is much, much better.

You want to use MOSFETs, then your choices are either use an OPT, or Circlotron, and keep 'em as far away from Class B operation as you can, which will mean big heatsinks. The X-over behaviour is hideous.

[foo]

Output trans has a good character of isolating the speaker from the feedback loop. I think it will improve the sound of a global feedback designed amp.

[GlidingDutchman]

Originally posted by Andre Visser
Now why would you want to ruin the sound of mosfets with a transformer?

Hi daar Andre! Ek het `n stuk Steinhart gekry... wil die OPT gebruik...

[Andre Visser]

Originally posted by Miles Prower
You want to use MOSFETs, then your choices are either use an OPT, or Circlotron, and keep 'em as far away from Class B operation as you can, which will mean big heatsinks. The X-over behaviour is hideous.

OK, mine run in Class-A and I’m very happy with the sound quality.

My opinion is that transformers are quit good for power supplies, not for audio signals.