Amp out grounded, power supply as output, why?

[adason]

Encouraged, i added the output stage. Well, good news, bad news. Good first, it works. Bad news, i draws too much current. Vr4 is at min, and still too much current.
How do i lower it?

 

[adason]

Correction...i meant vr1 has very 'little' effect...i dropped the word 'little'.

Good news, i found mistake, swapped accidentaly drain and source. Now it drawes correct amps. Sounds great, actually.

Still in testing mode, getting to know the interplay betweet trimmers.

 

[N101N]

The output stage has voltage gain, since the output devices are operated in the common source mode.

In push-pull mode having voltage gain.

 

[nigelwright7557]

The output stage has voltage gain, since the output devices are operated in the common source mode.

Did you mean common drain mode ?
The output comes from drains via 30 volt supplies.

 

[wg_ski]

If the output comes from the drain (and the input into the gate) it is common source. The “common” terminal is always the one at AC ground.

 

[patrick101]

First section works fine, 100 ohm pot has very little effect, but 500 ohm affect distortion a lot, its lowest at max settings, so i may insert some resistor there, rather than changing the pot.
Vr3 works perfectly to adjust dc balance, vr1 not so much.
I like it so far.

vr1 is setting the jfets current, correct current for low distortion, vr2 may be the feeback control (gain and distortion control).

 

[N101N]

If the output comes from the drain (and the input into the gate) it is common source. The “common” terminal is always the one at AC ground.

That relates to a single stage amplifier.

 

[U130421]

See bi-circleton

 

[adason]

Yes, vr1 sets the jfet current, but it affects dc on output as well
But no matter what position, adjusting remaining trimmers accordingly it has very little effect on sound
Vr2 however, controls distortion, and messes up dc balance, it has to be adjusted carefully as it has profound effect. You can go from great sound to distorted in a blink of an eye
Vr3 is master dc control and works great
In their later scheme with servo, they used smaller value trimmer flanked by bigger resistors, to allow for finer adjustment
Right now its little touchy
Vr4 sets current
This is nice sounding amp, i am still using it withjust a test speakers, but i decided to finish it to the box with final power supply. Right now its powered using test power supplies through variac
One thing i changed, that grounded output. It presented no advantage in my case
Cheers

 

[adason]

some pics of the birds nest

 

[adason]

Lot more amplifiers with the same outputs.
Does anyone has stock?
2SJ200/2SK1529pp 2stage power amplifier