Singleton Input Stage Amplifier

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Thanks for explaining the biasing, yes it makes sense to apply any correction to a point where "no signal" is present.


Audio Power Amplifier Design Handbook, 5th Edition ,chapter 16, pages 429-430

Douglas Self states that...

...So long as the input is properly AC-coupled (DC-blocked) the trim current can also be fed into the input at point A, but the possible effect on the noise and hum performance is less predictable as the impedance feeding the amplifier input is not known.

Rod Eliott also uses the feedback point for injecting the dc voltage value for controlling the dc offset voltage at his P37A project.
 
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One way is to use the cursors on the output waveform and set them say 1us apart on the upward slope and then repeat on the downward slope.

This (its not your amp) shows the input set to 40 KHz and the cursors approx 1us apart. The slew rate here is just over 21 volts per microsecond.
 

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Hi,

This amp reminds me of my TGM3 where I also grappled with the dc-offset stability.

http://www.diyaudio.com/forums/solid-state/167369-designing-tgm3-output-triples.html

Look to post 128 for a single transistor dc-servo solution. It does product a turn-on wobble in the speaker (as do most dc-servo's) but this would be taken care of with a relay speaker protection board with delayed turn-on.

Look to post 123 for how to make the dc offset stable without a dc-servo using a few diodes.
 
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