Thank you very much for the assistance, especially the recommendation on the transformer.

The audible clicks aren't' heard when changing volume on the 990, only when passing IR through my URC MSC-400 controller. The controller is currently connected with a master IR-input which is automatically echoed out to 12 output ports. 6 of those ports are double-duty and can also be used for serial connections. One of them is currently assigned to be serial and is connected to the 990, though I have yet to employ full use of the serial commands since I'm still programming the controller. I've sent individual commands during testing however.

I see two things troublesome in this setup. #1 is that the IR signals are not completely isolated from the port where I have the serial cable plugged in on the MSC-400 even though I have it set up for serial use, not IR (using URC-branded serial cable). #2 is that the 990 is making audible noise in its audio path when receiving communication over its serial port.

Do you have any links for a suitable transformer that might already have an RCA connector on one end? I'm coming up with matches for products that have a phono connector built-in like this one:

http://www.americanmusical.com/Item--i-A...0807AFLHAMS0000