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subwoofer slight hum

I've tried and tried and just can't seem to find a solution so far.

It's not a big problem... I mean I have to get kinda close to the sub(s) to hear it, but there it is: a subtle but distinct hum down there.  

It used to be annoying with a throbbing pulse hum when watching TV or dvds, noticeable.  I solved that by plugging the subwoofer into a separate house circuit, with an extension cord.  I think that throbbing had to do with the "old" plasma TV drawing cyclically from the same outlet or some magnetic interference, I dunno I'm not an electrical engineer... (but it's the Panasonic ZT-60, which I still adore and won't part with soon).  Anyway, thankfully, the throbbing went away when I put the sub on a different outlet.  

But the hum down low still exists, both on the main listening and viewing room, and on another sub in a totally different part of the house.  

I've tried different cords, different surge protecting power strips including recently the Tripp Light Isobars (which I actually kinda like) but even they didn't stop the hum. 

I can live with it, I mean I can't hear it with even quiet music playing, but short of spending $1000 on some power conditioner or other, which from what I understand have mixed results at best (though I suppose that depends on the individual situation)... any ideas?  Might a $400 power conditioner do the trick, or is there some even less expensive possibility that I'm overlooking? 

curtdr
fstein's avatar
fstein
197 posts
 

Is your interconnect shielded?

erik_squires
15,657 posts
 

If you have a coaxial cable coming in, like to a set top box, you may need a ground loop isolator for it.

That's a quick fix otherwise, some questions:

 

  • Is the sub power connector grounded?  They don't all have a ground wire.  If it's not grounded it is unlikely to be a ground loop issue and more likely a power supply issue.
  • Sometimes you have the option of running XLR, which often have ground lift switches.... use that as an alternative.
  • Does the problem go away if you unplug the input from the sub?
curtdr OP
348 posts
 

1. Two separate systems, in two different rooms:  the coax interconnect on one sub is indeed shielded, and the speaker line input on the other sub is good cables... they both have the same hum

2. The sub power is not grounded... just a two prong plug

3. no xlr option

4.  and no, even if the inputs are unplugged, the problem does not go away.  The hum kicks in as soon as the units are plugged into wall outlets.  

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