Axiom Home Page Forums General Discussion Advice from Axiom Owners Subwoofer hum

Although there is a piece about hums in the tips section, I wanted to throw this out to the forum. I am getting a loud hum from my EP125 (further description below). Is this likely to be a ground issue or are there other things I might try?
My setup is a Denon AVR-1803 with Epic Mini+ (M0ti, VP50, QS4s, EP125). The subwoofer connection is from the receiver’s pre-out to the low level in on the EP125. The hum is audible at anything above a 25% volume setting and while it is dependent on the connection to the 1803, it is independent of the volume setting on the receiver (it goes away if the volume is zero but once present, does not get louder as the volume increases). My DVD player is connected to the 1803 via an optical input and there are no other inputs in use (no satellite/cable boxes).

Thanks!

Hi jonjons,

Hmmm. Very interesting. Try disconnecting your coaxial line-level cable at the subwoofer end right after you've been running the sytem, so the subwoofer amp hasn't yet cycled off for lack of a signal, and see if you're still getting the hum. If you are, call Joe Vassallo, Axiom service manager, on our toll-free line and he'll take it from there.

However, I'm almost positive it's a ground loop. Have you tried reversing the AC plug--if you can--on your receiver, and then listening? Or re-connect the line-level coax to the sub and reverse the AC plug on the subwoofer. Do one or the other, not both, and see if the hum disappears.

Regards,

Hi Alan,
Thanks for your help - I think I figured out what is going on. The hum goes away if I unplug at the subwoofer end but not at the receiver end! Part of the cable routing is inside a wall so there must be a source of electrical interference there (it also goes away if I use a short direct run). I guess my choices include re-routing the cable or using something other than unsheilded 16 guage.

Thanks again,
Jon

Jon, maybe I didn't follow your description, but are you saying that somehow you're using an unshielded 16ga connection to the sub rather than shielded coax?

Hi,

Good detective work, but yikes, you can't use unshielded 16-gauge wire for any low-level connection!! No wonder it's picking up hum. When you explained, I thought, "how unusual that shielded cable is still picking up AC fields" but now it's clear.

You must use shielded cable for all but speaker (high-level) connections.

Regards,

apparently they hum because they don't know the words.....





sorry; slow day at work