Sir Tony,
What I do now is to turn volume to zero AND put speaker selector to none (choices: none, A,B,A+B), this way I avoid the loud noise....but this is a band aid remedy and I am more interested in solving the root cause.
I know nothing about electricity but could this be caused by the capacitors discharging their electricity when the power is switched off?
My new amp also gives a slight clicking sound when switched off (but you wont hear it unless you put your ears very near the unit). Ano po bang mga piyesa ng amplifier and masasabi na may "shelf life" and should be replaced after a certain period?