Whine while running - tower only

[David Analog]

Jeff,
I re-read your OP. Did you indicate that you still have noise on the tower speakers with the input RCAs of the tower amplifier disconnected at the amplifier end?

[JeffCook3]

Yes David that is correct.

[David Analog]

Okay, I originally overlooked that because of the 'DC' abbreviation.
Open RCAs can still pick up noise. So use 1/2 a short RCA cable to short the left input to the right input and try again with the gain at no more than 60%. You should be noise free. Let's assume you still have noise.
1) Triple check that amplifier ground.
2) Disconnect both outputs. Use a 2-conductor wire to test a substitute speaker (any 'other' speaker) laying on the floor. If you have noise then send back the amplifier. If the noise disappears then the issue is with a) the tower harness, or b) one or both of the speakers.
3) So next isolate an existing tower speaker by using a new harness wire. If the noise disappears you likely have a wire strand touching something it shouldn't in the tower. Test the tower for voltage with the tower system playing. The presence of voltage would indicate a wire to tower short. Also test the tower for continuity incase it is grounded. The tower should be totally neutral in both cases (pos. and neg.).
3) If the noise is still there then isolate one tower speaker at a time. It's unlikely but a crossover inductor that is open at one end could become an antenna for EMI or RFI.
4) Temporarily change the physical location of the tower amplifier in case it is too close to a strong electromagnetic field, like a battery for example.