Audio circuit problem

[waqas5304]

Hi
U1 and U7 are the instrumentation amplifiers (INA163UA). U1 and U7 are supplied with + 15 V all the time .U1 & U & are two different microphone circuits.S1 And S2 are two different Audio amplifiers SSM2211. Both drive headphones.S1 has 5 Volts as power supply all the time whereas S2 is switched On / Off by switch in 5 volt supply path. Both the circuits shown in diagrams are on same PCB.
Problem:
When the microphone (5 ohms symmetrical) is plugged in input of U1, the signal from this circuit should not be audible is headset at S2. But I can hear distorted signal in headset at S2. Visa versa When the microphone (5 ohms symmetrical) is plugged in input of U7, the signal from this circuit should not be audible is headset at S1. But I can hear distorted signal in headset at S1.
When the SSM2211 S2 is powered OFF, the problem is solved. As soon as the S2 is powered on the same problem comes again.
I thought that the problem is due to the Power supply than I separated the powers supplies of both Audio Amplifier S 1 & S2 but the problem is still there.
Is this the cross talk or some ground loop problem ?
I hope you can tell me the solution. Thanks in advance
The circuits are attached as attachment
waqas

 

[FvM]

I have no clear explanation yet. Crosstalk would be just another word for the observation but doesn't clarify the signal path. A ground loop actually may exist. My first question is, if the channel sourcing the crosstalk is actually overloaded, so a distorted signal is present in this channel? The headphone amplifier would be first candidate for overload, cause it has the highest gain. By reducing the possibly overloaded headphone amplifiers gain for trial, you could check the assumption.

If the amp verifies as crosstalk source, you still have to find the path. By reducing gain of individual stages starting at the frontend, you can try to identify the receiving node (could be more than one in case of a ground loop). Measures, that may be also tried is adding bypass capacitors to supply and virtual ground nodes, e. g. in parallel to R5, R95, R105. By the way, in the schematic, there is a floating virtual ground node at U2.5, U2.10, U3.5 and U3.12. It would cause problems if actually existing in the circuit.