Studio Reference Amplifier

[apexaudio]

Originally Posted by Tekko

Mr. Apex, is it me or do all of your amp schematics look the same ?

You can see in all my threads completly different amp topology, but look similar becouse of drawing. Just compare this schematics: MOSFET Amplifier IRFP240/IRFP9240 , Tube/Mosfet 100W Hybrid Amplifier , 500W PA amplifier with Limiter , LM3886 Schematics + PCB , 100W Ultimate Fidelity Amplifier ...
Regards

[macd]

Originally Posted by apexaudio

Schematic with corrected caps voltage (100V instead 63V)

Hi Apex.......Do you have PCB for Studio Reference amp.........

Regards,
Macd.......

[apexaudio]

Originally Posted by macd

Hi Apex.......Do you have PCB for Studio Reference amp.........

Regards,
Macd.......

This circuit is made for test useing pcb from DC Servo Mosfet Amp (see post #4). Final version will be more powerfull with add another two pairs outputs in triple darlington topology (adding MJE340/MJE350 as predriver). I will share pcb for final version, and diyers with more expirience can use this circuit for design own pcb. Power of this amp is enough for small studio monitor speakers, but for large studio monitors power must be increase up to 200W/8R RMS useing 3 pairs of outputs.
Regards

[apexaudio]

SR50 is Studio Ref Amp for small studio monitors without cascode in VAS.

[apexaudio]

Pin layout for MPSA42/92 on Regulated PSU pcb is incorrect, this is correct pcb. Pin layout on first pcb is for BC639/640.

[apexaudio]

SR200 Studio Ref Amp for large studio monitors.

[stratus46]

Originally Posted by apexaudio

SR200 Studio Ref Amp for large studio monitors.

Every time I see a servo amplifier with an integrator in the feedback loop I cringe. Integrators MUST dither to run which means the output MUST be slowly cycling pos/neg to work. Has anybody tried using an operational transconductance amp for this job? That type of amp will converge and settle with no dithering. It made a massive difference in my DC restored video amps.

G²

[apexaudio]

Originally Posted by stratus46

Every time I see a servo amplifier with an integrator in the feedback loop I cringe. Integrators MUST dither to run which means the output MUST be slowly cycling pos/neg to work. Has anybody tried using an operational transconductance amp for this job? That type of amp will converge and settle with no dithering. It made a massive difference in my DC restored video amps.

G²

Amplifier DC offset is about +/-20mV without DC sevo, and no matching transistors are used. Offset is stabil after few hours, so there is no pos/neg cycling, just litle DC current thru RCR filter (220k-220nF-220k) in base of input transistor to compensate unmatching. Amplifier can work without DC servo or can use trimpot to set offset, but I think this cicuit is best way. Feedback for DC servo use 1M resistor and there is no influence to GNF.
Regards

[stratus46]

Originally Posted by apexaudio

Amplifier DC offset is about +/-20mV without DC sevo, and no matching transistors are used. Offset is stabil after few hours, so there is no pos/neg cycling, just litle DC current thru RCR filter (220k-220nF-220k) in base of input transistor to compensate unmatching. Amplifier can work without DC servo or can use trimpot to set offset, but I think this cicuit is best way. Feedback for DC servo use 1M resistor and there is no influence to GNF.
Regards

I'm not disputing the servo idea, just if it's been tried without the integrator.

G²

[apexaudio]

Originally Posted by stratus46

I'm not disputing the servo idea, just if it's been tried without the integrator.

G²

I'm sorry for my bad English, can You post schematic for servo with OTA?
Regards