Bazaar buzz

Even with interconnects from amp plugged into the pre, on or off, plugged into wall outlet or not, I still get a buzz/hum, though it appears to change the sound of the buzz/hum, but not the volume of it. 
I tried different interconnects and some are worse than others. The unshielded one being the worst offenders. 
Tried unplugging all kinds of stuff in the house to see if that would help to no avail. 

Do you mean across the interconnect rca plugs?  How does one do this?

I noticed today if I unplug on IC lead while amp is on the buzz goes away. This is while the other IC  is still connected   

I don’t have any shorting caps. All I know is:

no IC’s connected = zero buzz/hum

two IC connected to amp but NOT preamp (just hanging loose) = buzz/hum - loud in dB. Also if I move an IC around buzz/hum changes a bit in intensity. 

two IC connected to amp and preamp = buzz/hum - lower in dB but definitely there

one IC connected to amp and preamp, but the other not connected at all = Zero buzz/hum. 

Just an update I just used a standalone transformer with the amp, and all the buzz and hum appears to be gone!  I say “gone”, unless you put your ear right up to the woofer and then you can hear the slightest, slightest hum/buzz. Certainly not audible from the seating position.  If you put your ear to the tweeter or mid range you just hear your normal hiss, with no other artifacts. 
I’m assuming this points to dirty AC, correct?