What is disconcerting is that the OP bought 2 different P5s (1 silver, 1 black) from 2 different dealers (1 dealer was Audio Advisor) at about 6 months apart.
Yet, both P5s had the same exact noise problem.
I have followed this thread with interest.
I guess Parasound did not want to use a digital volume control.
These days there is a problem, as ganged pots are virtually unobtainable. So circuits have been developed that allow control of as many channels as you want with one mono cursor.
Now since op amp have become common the usual variable resistor inline with the audio signal has been out of favor a long time. The better way to control volume is to have the pot modify the feedback loop of the op amp. This has the advantage of raising headroom and lowering noise as the volume is decreased. However it still takes a pot per channel.
Now that ganged pots are virtually unobtainable, there has to be another solution to analog volume control.
One way is to alter the control voltage to the chips in all channels at one time with a single pot. This produces excellent tracking.
However, I have found out that any noise in the control voltage circuit is enormously amplified. So the single pot that in the old fashioned approach would be fine, now isn't.
I have looked at various ways to solve this.
One way is to increase the control voltage by a factor of 10 and then attenuate and filter it. This seems to work quite well.
So if this is the case with the Parasound, then the control voltage may not take into account the noise that can creep into the control voltage control circuit.
Back in the day, manufacturers used to issue the full circuit in every user manual. Quad always did this. Peter Walker, and others, were only too pleased to have knowledgeable customers improve their products, and were always grateful for an assist.
In a problem like this it would be very likely others would assist with this problem if the circuit were included.
