I have been noticing an odd thing with my ST-70 and PAS-3X combination. I can hear AC switching impulse noise rather loudly in the left channel, but not at all in the right channel. This seems odd. I would think that any such impulse noise would appear equally in both channels. I have another PAS, a PAS-2 that I have restored recently. I plan to substitute it and listen a while to see if there is any difference. I hear this noise if I turn on or off an overhead light in the same room as the equipment or if the washing machine cycles in the laundry room (on a different AC breaker & circuit). I do note that in the ST-70 the two channels have separate filament windings from the power transformer. Each filament winding has 1/2 of a double .02mFd capacitor bypassing its center tap to ground. The ground point is not the same as the star-signal ground near the electrolytic capacitor. I am wondering if perhaps one side of the double .02mFd disc ceramic capacitor used could be open and cause this problem, or if it might have something to do with the center point of the part that is grounded not being grounded at the same point as the star-signal ground.
Has anyone else noticed such an issue?
Joe