[haneyrm]

Hello,

Quick question.  I searched and cannot find a situation similar to mine.

I took delivery yesterday of a used HT-3.  I plugged the amp in and turned it on yesterday morning and let it warm up all day.  When I got home last night, I noticed an audible hum coming from both my front left and front right speakers.  Sounds like a ground loop.  I currently have the amp hooked up in a stereo configuration but plan on moving it to my home theater in a few weeks.  The thing that concerns me is that the hum is there no matter what I do with one exception.  I am currently using RCA cables to connect the amp to my Anthem pre/pro and as I said earlier, I have it set up in a stereo configuration with only the left and right channels connected.  As configured, I get the annoying hum.  If I change the configuration so that I am using either the left or right channel in conjunction with the center channel, the amp is dead silent (which is what I expected).  I guess my question is why am I getting a hum through my speakers with the left and right channels connected but when I use either left/center or right/center combinations the amp is completely silent?  This amp replaced a Parasound A23 which I still have.  I hooked it back up last night just for kicks and got no hum.

Any assistance would be greatly appreciated as I really like the amp and would like to keep it but do not think I can live with the hum.

Thanks,

Mike

[haneyrm]

I forgot to mention.  There is nothing hooked up to the pre/pro other than the amp.  I had my DVD connected via Toslink and even disconnected that trying to isolate the hum.  The pre/pro operates with a 2 prong cord.  I tried a 2 prong extension cord on the amp and the hum is still there.  If I disconnect the IC's, the hum disappears.  With only one IC connected, the hum is not there.  It is only when both IC's are connected to the L and R channels, I get the hum.

Thanks,
Mike

[DMi]

Sure sounds like a possible electrical ground loop.

I own an HT-3 that was upgraded from a Stereo Plus unit. I suspect that the IC cables do not have a good shield or perhaps something else is attached to the preamp creating another ground path. In my case I had to lift the power ground and change IC cables and the hum went away.

The HT-3 chassis is fairly packed and since you haven't mentioned hum from the center channel I'd bet it is a newer board and this unit was also upgraded so the stereo channels are the left and right ones. Those do sometimes exhibit issues with hum and additional sensitivity to finding ground loops.

In fact before I moved to satellite from cable I had a nasty loop formed by the cable ground and the pre-amp wiring that annoyed me with the stereo plus unit. Just disconnecting the cable TV feed made everything clear up in the audio of the system then.

[haneyrm]

Thanks for the info.  I moved this past weekend and plan to hook the amp back up tonight at my new house and see what happens.  I am not certain what vintage HT-3 I have but I do know that it was purchased in 2005 and it has 2-red circuit boards inside with the cap upgrades.  Does anybody have any pictures of the HT-3 internals that you can send me?  I was going to pull the lid off of it tonight if it is still humming just to see if there is anything obvious wrong.  Does anybody know if both circuit boards should be grounded to the chassis or how they are grounded?

Thanks,
Mike

[bondmanp]

FWIW, I have had an HT3 for almost 3 years.  Mine is unique - it has the newer boards for L/R channels and an older board for the center.  I have the EXACT same issue that you do, although the hum is low enough to ignore most of the time.  I'd prefer, of course, to have all 3 channels as quiet as the center.  I spoke with Klauss and his assistant several times about this, and they feel strongly that it is an "environmental issue" - meaning ground-loop.  They did have me remove an additional ground wire from inside the chassis - something about it being grounded too much, IIRC.  Call Klauss and see if he recommends you do the same.  There are numerous filters which can be placed in line with your video signals that might help, but in your case, perhaps upgrading power chords might have some effect.  Although Klauss does not encourage power filtering devices, I may eventually try one that I can return if it doesn't help or makes things worse.  Please keep us posted! 

[haneyrm]

Thanks for the reply.  I got my entire home theater hooked back up last night and the amp is humming as usual.  I had a message on my phone this morning from Klaus and plan to call him back tonight.  He said in the message that I should plan on sending the amp back to Odyssey for them to look at.  The only thing I have not tried is taking the amp to somebody elses house and trying it.  I am new to this area and don't know anybody that participates at this level or even has a preamp I can try.  I will keep you posted after I speak to Klaus tonight.  Do you happen to know if your amp has a ground wire from both circuit boards to the amp chassis?  I did notice that my center channel board has a ground wire from the board to the amp frame.  The L/R board does not have this ground wire.

Thanks,
Mike

[klaus@odyssey]

Yes,  I'll talk with Mike,  but I can already pretty much guarantee that it is a ground issue.  Also,  has been a used unit,  so it is always difficult to figure out what happened,  but we will take care of it,  under warranty,  of course.

Late,

Klaus

[haneyrm]

Klaus,

6 months later and I am about to give up on the hum issue.  I have tried everything under the sun external to the amp including dedicated circuits, different pre-amps, cheater plugs, new interconnects, balanced interconnects, voodoo and rubbing Buddah's belly.  I am using Klipsch Ref 7 speakers which are ridiculously sensitive and seem to amplify buzzing and humming.  My Parasound amp will make a very slight, almost inaudible hum.  The Parasound has gain controls on the rear panel and by simply turning the gain down slightly, it is dead silent.  Is there any way to turn this thing down a little to quiet it down?

Last we spoke, you did not think sending it in for a warranty service was a good idea because of the time it would take.  How does your schedule look these days?  I really like the amp but I am about to throw in the towel if I cannot get it quieted down.

As a refresher.  I am using an Anthem AVM30, the Odyssey HT-3 for the fronts and a Parasound Halo A23 for the rears.
I am also getting a very loud "pop" when I turn the pre-amp on.  I leave the amps on continuously.  I get nothing through the Parasound, only the Odyssey.

Thanks,
Mike Haney