Hum coming from Left and Right channel - RCA to XLR Adapter

I have a Classe SSP-800 processor which runs through a Gryphon Diablo 300 Integrated amp for the left and right channels. The other channels run through a 5 channel Krell TAS.

Historically I would run my Home Theater through a Ayre PreAmp which had XLR Inputs for L/R Home Theater Bypass. The Gryphon only has unbalanced RCAs for its Home Theater Bypass.
For some reason I get a humm out of both the left and right channels when watching a movie--Its not loud, but still annoying. I upgraded my cables, but still have the humm.

Since I never had this with the XLRs I was thinking of trying some XLR to RCA adapters out of the processor so I didn’t have to use the unbalanced connectors on the processor. Thoughts? Do these work that well.

There is not a humm on any of the other inputs on the Diably 300 so I suspect it is the outputs out of the SSP800.
No, that would not be a good idea in this particular case.

Most XLR-to-RCA adapters short the signal on XLR pin 3 to ground (XLR pin 1). While that is appropriate when adapting to an XLR input, and is also often appropriate when adapting XLR outputs which are transformer coupled, it would be inappropriate and perhaps even harmful in this case. According to the SSP-800’s manual pin 1 is connected internally to signal ground (as opposed to chassis ground), and the output impedance of its analog outputs is only 56 ohms (although it is unclear whether that applies to the unbalanced outputs or the balanced outputs or both).

So using an adapter as you propose would most likely result in shorting a signal supplied from a particularly low impedance output directly to signal ground. Which in turn would stand a very good chance of causing problems eventually if not sooner, including even the possibility of damage. For example, see this thread.

On the other hand, I believe that Cardas can supply adapters on special order which leave pin 3 unconnected. Or a cable supplier could custom make an adapter cable which accomplishes the same thing. But FWIW my guess is that neither alternative is likely to resolve the problem.

What is likely to resolve the problem, IMO, would be inserting a suitably chosen Jensen "Iso-Max" transformer between the two components, although they cost ca. $250 to $300:

-- Al

Al,  Thanks for the very thorough response.    Sounds like i was definitely headed down the wrong path.   I'll give the Jensen transformers a try.

if there is a hum there is a ground loop.  the transformers suggested above will fix it but it should be able to be fixed with a cable.  if you can solder you could build a cable for $10 that would test this.   I would also check if the A/C plugs for both the classe and the griffon are plugged in the same direction.   

The other option is that there is a ground differential between something connected to the classe and the griffon.  unplug all inputs and outputs from the classe including those to the tv and connect them to the griffon.  does it still buzz?   Add them back in one at a time to see what causes the buzz.