Unusual amp from 1987

[stanislav1957]

The voltage is constant at the output of the opamp look. And check the limiter.
The LMC option is then preferable.

 

[minek123]

There is small offset 1.4V on the output of op-amp
With your LTP+CCS output offset is almost 0.

 

[stanislav1957]

Okay. I'll archive this option. then maybe I'll work with him.

 

[minek123]

My PCBs arrived.
This is work in progress for schematic from post #1020
https://www.diyaudio.com/forums/solid-state/357369-unusual-amp-1987-a-102.html#post6463786

 

[stanislav1957]

Okay. I'll archive this option. then maybe I'll work with him.

I decided to remove the OE from the signal chain. It turned out well. The loop gain graph shows a large margin of stability .
A balanced amplifier is next in line.

 

[stanislav1957]

Promised

 

[minek123]

I decided to remove the OE from the signal chain. It turned out well. The loop gain graph shows a large margin of stability .
A balanced amplifier is next in line.

I see you changed arrangement of Q3, with extra feedback from the output...

 

[minek123]

Promised

Thanks Maxim! I'll sim it, this could be next build candidate.
As you know, I was thinking about symmetrical version..

 

[stanislav1957]

I see you changed arrangement of Q3, with extra feedback from the output...

Classic.The Composite Young. an inverting composite amplifier, where the discrete part is a non-inverting voltage amplifier .

 

[minek123]

I'm hoping to start testing amp from post #1020 this weekend.
1 board is completed and ready.

 

[stanislav1957]

I see you changed arrangement of Q3, with extra feedback from the output...

Thanks Maxim! I'll sim it, this could be next build candidate.
As you know, I was thinking about symmetrical version..

П

Throw out the opamps and you get the L. Zuev amplifier .Radio magazine No. 2 No. 3 2005

 

[minek123]

Where to find it ?
I thought Radio magazine was discontinued in 2000?

Архив журнала <<Радио>> only shows issues until year 2000.

 

[stanislav1957]

Radio magazine No. 2 No. 3 2005
02.zip - Google Drive

 

[minek123]

Got it! Thanks.
Looks like a CFA amp...

 

[stanislav1957]

????? ????????? ?????

 

[minek123]

Yeah, this is CFA. Voltage shifter similar to yours.
Needs op-amp for DC Servo.

 

[stanislav1957]

We all take the best from each other

 

[stanislav1957]

Thank you very much for the literature.

 

[minek123]

Just started testing the amp from post #1020


So far - at first attempt, with rails at +/- 12V, and without input signal,
it's oscillating at 154kHz. Looks kind of like sinus, but only upper halves.
Vpp 9V.
Zobel resistor gets hot.

With PSU current limiter at 200mA, negative rail will start sagging when increasing rails voltage beyond 9V.

Will try with full rails voltage (+/- 45V)..
Update: same thing. 154kHz oscillation at higher Vpp. Negative rail stuck at 8V. Zobel hot. Current limiter at 200mA.

 

[stanislav1957]

Turn off the limiter diodes temporarily. C7 increase to 270pf. R20 is better to increase a little