Studio Reference Amplifier

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
 
SR50

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

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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.

 
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.


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
 
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.

 
Just an observation, Zeners provide a fixed voltage drop but don't provide a fixed voltage to
the collector of the input pair.
So Zeners don't really do the same job as the cascode.

Also aren't Zeners rather noisy in this position?

Voltage on collector is fixed anyway, transistor give gain with diferent collector carrent, collector voltage difference is les than 0,5V in linear area before saturation (non linear area with high THD, amp clip)
 
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