Audible Hum

Thanks to everyone who posted an answer. It turns out that the cheaters plugs did the trick!!! Thanks again.

Turns out I had a dual problem. Primary one was cable TV ground problem. Tried to resolve it by rewiring the cable box, but the morons have grounds to the electrical system, gas pipes, etc. Ended up buying an inline device by a company called Viewsonics from a local audiophile store for $30. Their Web site is www.viewsonics.com, though I didn't see this filter listed. The other problem is was sort of mismatch between the amp and preamp. In addition to calling the pre's manufacturer (still waiting for a call back) I floated the ground on the pre and the noise floor is vastly quieter. Finding the problem, as Bob said, involves starting at one end of the system and working back to the other end.

One thing I recently found helpful, is try unplugging the inputs to your preamp to see if it goes away. I had my TV connected into the aux input, TV's are a great culprits of hum because there antennas are grounded. This solved my hum problem, and it wasn't present with the previous preamp.

I had the same problem with different components, but the fix was the same. I put a cheater plug on my preamp and my system has not had any hum problems since.

P.S. Checkout the chat topic "AC grounding" on the same list as your post

I had the same problem with my ReQuests.What you're probably seeing is a common ground loop. This occurs because of of all the grounds (e.g., the grounding pin on the power cords) on your equipment and the interaction with the shielding on the interconnects (grounds also). The most common solution is to use a 'cheater plug' (the small three-prong to two-prong devices)on the power cord of one component in you system. Experiment to see which component/power cord is the culprit.I actually had to use two on my system and it is absolutely quiet. Someone on another chat request suggests starting with the amp; I've also seen others suggest doing the experiment to identify the offending component. Remember though, you will be lifting the ground (Safety) from that component. That said, it is a fairly common problem and a fairly simple fix.