I just noticed all 5 of the tweeters in my speakers emit a hissing sound. I stumbled upon it accidentally, while dusting the stands. I have removed all components from the equation (i.e., physically unplugged) & have only the 970 connected to my power amp (Anthem MCA 50) via the 5 RCA preouts. Again, no other cables are connected to the 970. When I turn on the 970, I can hear the hissing. Adjusting volume/mute/input/etc makes no diff, only turning off the 970 makes it go away. I borrowed a friends old Yamaha 2 channel preamp & connected it to all 5 channels of my amp (2 at a time, of course) & I got dead silence every time. Slipping the 970 back in again yields the hissing.

I have tried 2 sets of quality RCA interconnects, from Monster & Bluejeans. Equipment is plugged into a Belkin PureAV PF30 power console.

What gives here?