Hum problems

[almonet]

I just installed a Behringer Tube Ultragain T1953 Microphone Preamp into my rack which is pretty modest with only a BBE 882i Sonic Maximizer, rack tuner and a Furman power conditioner. My problem is that I had never had a hum issue before installing the mic preamp, but now I cant seem to get rid of it - even without the preamp hooked up. I did however notice that it almost goes away when my computer is running on battery power as opposed to AC. Can anyone help?

 

[witzendoz]

Where is the lap top in the picture, so to speak? Is it hooked up to the gear via usb, fire wire or midi?

If it is you probably have an earth loop via the lap top and the audio / midi connections.

Is the power supply for the lap top plugged into a plug board / furman conditioner where the power for the rack comes from?

If it is there could be induced transformer hum from the Lap top power supply, try plugging it in somewhere else.

Cheers

Alan.