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Sub-woofer hum problem

Hi, I know this has been covered ad nauseum but my plebian brain can't come up with a solution. Here's the system: Wadia 850 cd player connected to an Eddie Vaughn Carina set el84 integrated amp in turn connected to Reference 3A speakers. I have a MJ Acoustics (REL) sub-woofer that is connected to the speaker terminals of the Vaughn via a Neutrik cable. I get really audible hum even when the amp is off and still connected to the sub. With the Neutrik connection disconnected from the sub there is zero noise, dead quiet, even when the amp and cd player are still plugged into the wall sockets. So my handful of brain cells tell me there is something not very synergistic going on between the sub and the amp. Any ideas greatly appreciated as I would like to use the sub to augment the speakers.

Thanks in advance, Cort Chambers
goofycarp
jmcgrogan2's avatar
jmcgrogan2
6,346 posts
 
Sounds like a ground loop hum. No cable tv involved anywhere in this setup? If no tv, is the sub plugged into a different outlet than the integrated amp? If so, try plugging them into the same outlet or power conditioner and see what happens. If this isn't possible, Google "ground loop eliminator for XLR", and look at your options.
Tube amps are very sensitive to both music and ground loop issues.
sidssp
1,077 posts
 
It is obviously a ground-loop problem. There are usually three ways to solve this.

1. Use star grounding. It means plug everything into one power strip.

2. Use cheater plug.

3. If both 1 and 2 failed, you can use a RCA ground-loop isolator like the Jensen SUB-1RR or SUB-2RR low frequency audio isolator. The SUB-1RR is for one channel, the 2RR is for two. They are basically input transformers. Since you are dealing with sub, you shouldn't hear any sound quality degradation.
goofycarp OP
3 posts
 
Thanks for the responses. I tried plugging everything into one power strip did not help and tried the 3 prong to 2 prong approach same result. So I will try the audio isolators and report back.

Again thanks for the directionl

Regards, Cort
paulsax
275 posts
 
may not be of any use but I found I can make my system do this (conditions sound similar) when my receiver is off and one of my main speakers is unplugged while my sub is connected to the receiver and the sub is powered on. My sub auto powers off when no activity and i was shutting down the system the other day. shut down the receiver (plugged in still) and unplugged one of my front speakers before the sub auto powered down. may be a complete red herring. sub and receiver plugged into different circuits, no tubes. not sure if this can help the poster or if it is even another symptom of a ground loop issue.
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