Do you have cable TV plugged into your receiver? The majority of HUM issues originate from this. Try unplugging your cable line from the receiver and note if the HUM disappears.
If yes - you can buy a filter for the cable tv line for about $60 and eliminate your problem permanently.http://www.jensen-transformers.com/
VRD-1FF Cable TV Ground Loop Isolator
Analog, Digital and Cable Modem Compatible
(Supercedes the Model VR-1FF)This is a voltage sensitivity problem, I have the same problem. The pro amps want 1.25 or higher and most comercial pre/pros, etc send out only .775. A few of us have this issue.
That's BS. Was the first time Penn posted and still is.
The truth - most, if not all modern pre/pro's are capable of outputting several volts from the LFE and pre-outs.
The Outlaw 970 specification is for 6 volts maximum from the pre-outs. Here is a link to the manual:http://www.outlawaudio.com/products/970.html
Maybe Penn could kindly post the make/model of a receiver that has specifications to only output <1 volt.
You might have a cabling problem - how are you connected from the Outlaw to the external amp?
I have always used RCA cable with a RCA to 1/4" mono adapter (rat shack $7) and never had a problem, even with pre-outs rated for 2 volts.
Also - check in the Outlaw settings that you have all speakers set to "small" and try a reasonable crossover of 80 Hz. If they are set to large, you are defeating the bass management system and might not be sending the sub enough signal (only LFE content).