Hum in preamp when using HT bypass

If you have cable or satellite hooked to the television, you may need a ground lift or something similar to a Mondial Magic inline with the coax. I was told I didn't need that for satellite but turns out I did, and it worked. I would believe the cable/satellite/television is the culprit before doubting the Sim P5. Your local HT dealer should have some sort of an in-line ground lift in the $10-20 range - a good place to start. Good luck.

Thanks Mitch for your reply but will this happen if I have 2 dedicated lines and the preamp and amp are plugged in one line while my video and digital is in the other line as I have right now.

Yes IME it can. Any connection between units having cable or satellite connections can cause hum. Consider if your DVD player or processor are hooked to the television (which is hooked to cable or satellite) and also to the preamp via an rca cable which has ground and positive, they then share a ground connection. I am not an expert, but a ground lift cured the same problem in my set up, when I was attached to cable, and then later again after switching to satellite.

I was going to suggest trying rca to xlr adapters, but you don't have XLR input for HT bypass.
so, most likely it's a ground loop from your catv. try disconnecting your coax cable from your cable box and then turn the system on to see if there is still hum. If the hum is gone, then get the Mondial magic box or something similar.