RB 991 hum question

[JimP]

I've had this RB 991 for several years as part of a 7.1 home theater system and have had a hum issue that may or may not be a problem.

Using XLRs to the prepro, if I disconnect the right xlr from the RB 991 amplifier, I get a loud hum. Connect it back and hum goes away. Disconnect the left xlr and no hum. (note that it only does this on one side)Disconnect both left and right xlrs, no hum. Changing the switch from balanced to unbalanced doesn't seem to affect it.

Is this normal or something I should look into? At the least, I'd think that I'd get the hum whether it was the left or right xlr but it only does this if its the right xlr that's disconnected.

Something else I'd like to ask. I also have a RMB 1095 that I use for the front 3 speakers and side surrounds. The RB 991 I use for the back surrounds. Is the RB991 better and I'd benefit by using it for the front r/l and use those two channels on the 1095 for back surrounds? Then when I do 2 channel music out of the front L/Rs, the sound should be better?

[JimP]

Patiently awaiting a comment.

[madmac]

Inevitably, hum is caused by either a grounding issue or bad wires. Check your wires and the electrical grounding. I suspect in your case though that you have a bad wire.

[JimP]

Its much louder than the typical 60hz ground loop hum.

I will swap out a cable and see if that makes any difference.

Thanks for posting.

[JimP]

Just got finished swapping cables out and the condition exist exactly as before.

Keep in mind that the RB 991 has only a two prong cable.

I think I'll open it up to see if there is anything obvious about broken wires at the xlr connectors.

[madmac]

Your average AV setup has many wires. Have you checked them all?. Are you using a good spike protected power bar?. What about your speaker wires?. I know, it's annoying when this kinda' thing happens. You have to slowly and methodically trouble shoot and try to figure out where the contamination is. Good luck.

ps....I am assuming that all wiring and connections have been properly done!.