Easy in principle, trickier to do in practice.
The hard part is determining the single value of resistor to replace all that network with. R316 and C312 stay but probably with altered values. R320 is the main DC feedback route and so somewhere in that ballpark is needed to maintain lowest DC offset. However, that will give an AC gain higher than you have now.
If you have a scope and sig gen (squarewave) then you could optimise it all better.
The hard part is determining the single value of resistor to replace all that network with. R316 and C312 stay but probably with altered values. R320 is the main DC feedback route and so somewhere in that ballpark is needed to maintain lowest DC offset. However, that will give an AC gain higher than you have now.
If you have a scope and sig gen (squarewave) then you could optimise it all better.
Remove all the components in that block and replace with three parts.
1) a resistor from the output to the inverting input (base of TR306), around 150k.
2) a resistor (around 5k) and a capacitor in series from the inverting input to ground.
The capacitor would be around 100uF 50V non-polarized.
There's an RC network across TR304/306 that should be enough, maybe with altered values.
Quite possibly. There is 27pf cap but it is padded down by the other series network parts.
I would definitely want to observe its performance on a scope and real load though.
You are best measuring the voltage across C1 (it will be very low) and fitting the cap to suit. It shows it as +60mv on the diagram but it could be say -25mv. So fit to suit the conditions.
The small cap would typically be around 6.8 to 22pf (picofarad) and a be a small polyester type ideally. Silver mica isn't to bad as long as the voltage rating is OK, say 100volt.
The small cap would typically be around 6.8 to 22pf (picofarad) and a be a small polyester type ideally. Silver mica isn't to bad as long as the voltage rating is OK, say 100volt.
The 100uF capacitor to ground reduces the gain at DC to x1 (0dB).
This normally results in only a very small amount of DC at the output, under 100mV.
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Hi White Rhino, the common way to do this is by using a "tone-defeat" switch which is achieved by a four-pole change over toggle switch. to cancel the bass you short circuit the potentiometer (bass control of each channel) at the same time you cancel the treble with a 10 Meg series resistor. If you don't follow I will make a sketch, but it is really straight forward. When the tone-defeat is on only the resistive elements are used in the feedback path.
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I have one comment for you Rhino and that is as soon as you remove all traces of the tone control there will come a time when you will kick yourself for the stupid decision. There is no such think as flat playback and the only way you will come close at achieving this is with a bass and treble control. Having a mid control would be an even further advantage.
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