I recently moved, and installed my home theatre audio system in my new place the same way as I had at my last place. My system consists of Axiom M22's, QS4's, a VP100, a powered subwoofer from another manufacturer, an Onkyo TX-SR605 receiver and Onkyo DVD player.

I noticed that I now have a very annoying buzzing sound coming from my speakers at higher sound levels. It is a higher frequency than 60 hz, but not a high frequency, I suspect it is a harmonic of 60 hz, such as 120 hz or 180 hz, etc. This sound was not present in the system at my old place. I searched the web and ground loops seem to be a big cause of this (especially the cable signal), but I have tried numerous suggestions and nothing has killed the buzzing.

I did notice that the sound is almost non existent when I place the receiver in Direct mode, which employs minimal signal processing. In all other settings, includig Stereo, the sound is present. The sound is also present through the headphone jack. All pieces of gear are plugged into a strip that is plugged into a single outlet. I have tried unplugging all inputs to the receiver, but this did not help. I tried unplugging the television (conventional CRT set), disconnected the cable from the wall, plugged the receiver into a different wall outlet, plugged the powered sub into a different wall outlet, nothing has helped. I don't think the speaker wires are picking up the noise because as I said I can also hear it through the headphone jack. It is possible that something in the processing module has failed, but not likely. I suspect the AC power, but am wondering why the power supply input filtering wouldn't take care of this. I did think to disconnect the receiver and move to a new location, plug it in, and see if the sound disappears using headphones. If it does, that would indicate some type of interference or power issue at the install location. If it is the same, then I would think that would mean something has failed in the receiver.

I love my system, it sounds phenomenal and is a joy to listen to whether it is music, movies, or just watching television with great audio. However, this noise is really bothering me and is seriously detracting from my enjoyment of an otherwise incredible sounding system. I posted this here as I trust the knowledge of the good people at Axiom and hope someone here can help me out. Thanks!

Hi MikeG,

The vagaries of ground loop hum can prove mysterious and very annoying. You seem to have tried almost everything. If you disconnect the low-level coaxial cable at the subwoofer input, then turn on the sub, is there any hum from the subwoofer itself? If not, then I still think you may have a ground loop. If there IS hum from the sub with no cables connected except AC power, then there's something wrong with your subwoofer amp.

Did you disconnect the cable-TV feed at the point it enters the cable box? Try that. If the hum disappears, then it's a ground loop from your cable system, and you need to order the cable-TV isolator from Axiom. If you still have hum after disconnecting the cable-TV feed, then I suspect there may be a defect in the Onkyo.

Did you try disconnecting all the inputs, audio and video, from the Onkyo, then listen using the headphone output. If there were a defect in the Onkyo amp or preamp section, you would still hear the hum. If the hum goes away, then it's a ground loop somewhere in your system and not the Onkyo.

Your AC power supply from the wall outlet cannot in and of itself cause hum; there has to be a difference in the grounding of other components, including the cable-TV feed, which is almost always the culprit.

Let us know the results.

Regards,
Alan

If you have any lights on dimmers make sure they are off, and see if the buzzing still exists. That was source in my system.

Good point, ClubNeon. I always forget that those dimmers can introduce hum and noise into a system.

Regards,
Alan

Mike, you don't live in Randy's basement, by any chance?

Sounds like you're doing the right things.

Take EVERYTHING apart. Add one component at a time, testing thoroughly between each one. Seriously - start with just the receiver and two speakers and listen to the radio.

It's a pain. You'll find it eventually. Keep the faith.

Are you using Audyssey EQ? If so, did you recalibrate after the move? If you did recalibrate, was there anything running at the time (like a tv/computer fan, HVAC, florescent lights)?

If you are using Audyssey, try turning it off to see if the hum goes away (or, more likely, reduced to almost not audible).

I can relate...from the buzzing I had with my MPS-1 Emo amp and closet light switch combination, or the low thumping from my old EP600 amp with lighting in the area, the list goes on and on.

Thanks for the help guys. I don't seem to hear anything from the sub, but it is a downfiring model and is tucked away where I can't really stick my ear next to it. There are no dimmers in the condo, not sure about the next door neighbor though. I'll try the suggestions offered and report back.

Forgot to mention, I didn't use the Audyssey, I set it up manually.

Don't be afraid of Audyssey, it is your friend.

Oh yeah?? Well I remember once going into a pet store and the guy there tried to sell me a kangaroo. He tried to tell me that it would be quiet, clean and would quickly become my best friend. I said "Yaa! Until he kicks my Ass!!, I've watched Looney Toons, you know."

Wait, what were we talking about again?

I thought you weren't drinking 'til you got home Murph?

No, it's pretty much all the time now.

Well, I performed some additional troubleshooting on the receiver last night. I completely disconnected it and moved it to to other rooms, powered up and listened through the headphone jack, buzzing still there. So the issue is with the receiver. I pulled the cover off to check for any loose connections that may have occured during the move, none found. Curiously, the buzzing has changed. Whereas before it was almost non existent on the Direct setting and very noticeable on all other settings, it is now almost unoticeable on Theatre Dimensional setting and clearly audible on the Direct setting (as well as all others). The unit is out of warranty now (I bought it as a Factory Refurb, 1 year warranty), so I doubt it is worth looking into getting it fixed as I can likely replace for the cost of the repair. Bummer.

Mike, just for the heck of it, try a good powerbar / surge suppressor thingie.

Usually, these ground hums are related to the interaction of different components' non-common grounding, or the issues of, say, your TV cable having a different ground source.... but that doesn't mean that it can't happen internally within a component. It's worth a quick try in case the receiver itself is picking up something from a refrigerator, dimmer circuit, or a neighbor.

Hi MikeG,

I think you've isolated the problem, however, there is one thing you might try. Does the receiver have a re-set button? Try unplugging it, then re-connecting it and powering it up to see if the buzz remains.

I have an aging H/K that seems to develop a hum in one of the main front-channel amps. If I turn off the receiver, then power it up again, the hum disappears and stays that way for a few weeks.

Alan

Yes Alan, you can reset the microprocessor, but I think that is more setup related type stuff. I've had it unplugged numerous times during my troubleshooting attempts, it didn't change the sound unfortunately. I can't afford a new receiver right now so as long as I keep it in Theatre Dimensional setting I don't really notice it.

Too bad to hear it is the receiver, I think I would still try a good surge suppressor or 'power conditioner' like some of us have, a Belking PF60 or similar, if nothing else it looks cool in the equipment rack and you get to see how many amps your system is drawing