Hum in preamp when using HT bypass


I have a Sim Audio P5 preamp that has an HT bypass input. AT first I was using RCA interconnects from CD to preamp, preamp to amp and the HT bypass and had no problems. When I switched to balanced from CD to preamp and preamp to amp leaving the RCA connection for the HT bypass I am getting the hum. There is no balanced input for the HT bypass. When I choose my CD input I do not get the hum, only when I switch to the HT bypass input. Any suggestions?
kayoboy
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Thanks for all the replies and suggestions. I tried to disconnect my coax to my satellite box and hum is stll there. I removed all my connectors one by one still there. Finally I switched the input from HT bypass to another input in my preamp and the hum is gone. Is the bypass input defective? Well maybe I will just do with this setup for awhile and just put the volume at 12:00 oclock as have been stated in other threads until I could have this fixed.
Sounds like an issue with the bypass circuit. Try another source through the ht bypass that doesn't hum normally, and if the hum is still there, it sounds like the circuit. Good luck.

Sim Audio tend to have great customer service.

kw.....
Is on a different AC leg at the AC Box
To test if this is the case just plug in the whole system into One outlet strip out of just one dedicated outlet
and the hum should be gone.
Next have an electrician place the dedicated line on the same leg.
Let me know if this fixes
Cheers Johnnyr