Volume control along ground loop breaker.

If you add a resistor between the amp ground and the incoming ground, then the negative feedback input is also referred to it.The positive input must have attenuation of the same ratio as the feedback to reject the voltage across the GLB resistor as common mode. The positive input attenuation must be precise or else the two channels crosstalk via GLB resistor 10ohms in bellow circuit.
If I install a standard volume control, this ratio will be modified.
I didn't find any example to follow, if you know any, please show it.
I designed one bellow intended for the "Bameless CFP" maybe it can be used for other amps. Max. attenuation is -60db.
Lower channel is without volume control as standard GLB.
This is applied on amp with FET input transistors.
volume control GLB.JPG
 
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