Bazaar buzz

Try plugging your interconnects into your preamp. Still have a buzz?

If you have interconnects hooked only into the amp, and not into your (or any), preamp, your amp will hum, as it is picking up RFI. You need to plug the interconnects into the amp and preamp to avoid this. 

Turn OFF amp and wait a few minutes before attaching to preamp!
(This is perfectly normal with an un-terminated input).Don’t connect to CD player!I’d turn off whatever preamp you're connecting, as well.
Steve

So if I plug my ARC Classic 60 into the wall with the speakers hooked up and turn it on I get no buzz. Please note that no other equipment is plugged in NOR are and interconnects attaches to the amp or any other piece of equipment.

Your getting an "open circuit input buzz", if you put shorting plugs into the input, the buzz should go away, same if you have preamps cd players or dacs connected. (The input needs to see a load)
Cheers George

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. 

Put a 30k Resistor across them and watch it go away. :)

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

Sorry misread your first post, as you have a buzz when the inputs are open circuit, but in fact it’s the only time the buzz is not there.
See if you have a buzz when you plug in some "shorting rca plugs" into the amp.

Cheers George

Just to add, if you have a Buzz still with the inputs both shorted, then the amp has a problem, and needs to be looked at.

Cheers George 

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   

You shouldn't ever unplug anything while the amp is on, this lead to blow ups.
Do what I said with shorting rca plugs. If it's their while both inputs are shorted, it needs a tech to look at it.

Cheers George  

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. 

Get some shorting rca’s plugs (not those stupid rca caps) it’s the only way "you" are going to find out if it needs a tech to look at it. Both channels should be quite when these are in. If not see a tech.

https://www.ebay.com.au/itm/Onkyo-TX-DS989-Stereo-Receiver-Parts-Original-RCA-Shorting-Plug-Noise-Terminator/173848128831?hash=item287a27ed3f:g:x74AAOSwkNFclo7J&frcectupt=true

https://www.ebay.com.au/itm/RCA-Shorting-Plug-for-Vintage-Fender-Pro-Reverb-Amp-No-Need-for-a-Footswitch/174113224229?hash=item2889f4f625:g:5C8AAOSw5VFWMAHP&frcectupt=true

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?

🤷‍♂️🤷‍♂️