Sorry but you should not do that, it should be fully disconnected, not just off. The preamp is seeing the idle amp as a load. Sometimes OK sometimes not.
Amplifier Damage
Had a question, can an amplifier's input stages be hurt, driving an audio signal through it while it is in Stand By/Powered down. The reason I am asking is I have two integrated amps hooked up to the DAC, one to the unbalanced out and the other balanced out. The one hooked up to the Unbalanced out was powered down while I was listening to the one hooked up to the balanced out for several hours.
Once I realized that, I disconnected the Amp powered off, Everything seems to work fine, but I had the nagging question. Does the input audio signal get shunted to ground through a diode in the input amp stages when its powered off or something to protect the circuitry?
Any inputs will be great