[floresjc]

Well, I moved into the new place and got my stuff hooked up again. One problem, I have quite a bit of hum coming through the speakers (and sub). Enough that I'm going to have to do something about it.

I'm not the most knowledgable on hum, but after reading some "hum vs buzz" basics on the web, I think I've narrowed down the issue.

I think I have ground loop issues, because my plasma tv is on its own dedicated circuit and the source and receivers on another. I believe the component and HDMI connections between my Outlaw 990 and my Plasma tv are transmitting the residual current, which is then feeding the rest of the audio chain through the pre-outs and into the amps. I kind of figured this out because if I unplug the video outs (thus cutting the tv from the rest of the system) its quiet as can be. Also, if I do a non-tv activity (like run my PS2100 for 2-channel listening) it also is quiet. Mind you the tv is still hooked up in that scenario, its just not on. It will buzz in passthrough mode, but if I switch the PS2100 to say the MP3 input, goes silent instantly, why it blocks it, don't know, but it does.

So does anyone know how to block ground loop differences over component and hdmi video circuits? I suppose they make isolation transformers for that, does anyone know of any good ones or where to get them? I suppose in the short term, I might try and unplug my tv from its own circuit and run the cord back to the amp plug in behind the wall and see if that helps. Its kind of a pain, since its mounted on the wall and I'd need to rehang it, but its worth a shot while I figure this out.

[sfox7076]

Where is the cable/coax wire plugged in?  What if you unhook that?  It has been my experience that that causes 9 out of 10 hums.  Not sure it is in this case, but it might be. 

[taoggniklat]

Are you sure it wasn't just you huming along with the music? 

J/k I hope you get it resolved soon, that would drive me nuts too.

[ctviggen]

Can you plug the TV into the same circuit everything else is on?

[avahifi]

The problem is likely a dirty ground connection on your incoming cable tv coax cable.  If you disconnect that at the TV or cable box, whichever comes first, it likely will resolve the issue, except then no TV picture.

The cure is an inexpensive isolator available at Radio Shack and similar.  The device goes on the end of the incoming TV line and isolates both the signal and ground side from the system.  These are done with either capacitors or inductors, both work, some better than others, ask around here at AC for the best version.

Regards,

Frank Van Alstine

[gerald porzio]

I use the Mondial Magic Box which was about $90. Pricey but very, very effective, nary a trace of hum. I've seen other isolation Xformers on parts sites from $10 & up. Mondial may be out of biz, but some audiophiles tout Jensen - again pricey but surely effective.

[Big Red Machine]

I vote cable and a ground issue also.  Try a Jensen unit.

[diablo561]

I would try this low cost solution, works for me
http://www.smarthome.com/81285/Xantech-Feed-Through-Surge-Protector-634-00/p.aspx

[floresjc]

Sorry guys, been gone all day.

Well, I would try cable, except I have no cable hookup on this tv yet. I get the cablecards Monday morning, and I haven't hooked the coax up yet, its just hanging on the back side of the wall. So no dice there.

The really strong evidence to me is the fact there are 2 circuits in play, and the tv is isolated on its own. They are each grounded separately, giving a good potential for a differential, and yanking out those video cords from the Outlaw 990 makes everything all better.

I have an electrician coming tomorrow at lunch (for a different reason entirely and he's a life long family friend), and I'm going to have him take a look. He can access both circuits behind the wall easily (its basically a closet underneath our stairs) and he can probably put both circuits on the same ground, but have them separately fed to the breaker box. I'm hoping that solves the issue, if not, I may have to spring for some of the units you guys recommend.

I'll let you know how it turns out. I'm just darn happy none of my Salk speakers or AVA electronics got damaged in the 1200 mile move, still sound great!

Edit: I would also add the cable would attach to my Tivo and fed through the 990 into the tv. Right now the only connections between the tv and anything else are the component and hdmi between it and the 990.

[Nuance]

1200 miles?  Wow!  I am happy to hear the move went well and I hope you get the hum issue resolved swiftly.  Do keep us posted.

[Niteshade]

The best way to seek out hum is through a process of elimination. Start with just your amplifier and preamplifier first. Unplug all your sources from the preamp. Start plugging them back in one by one until the hum comes back. Could it be a bad interconnect?