hum/buzz on speakers....

[pjwinstalls]

I have a hum/buzz on all my outdoor speakers. I have tried a ground loop isolator that plugs into the rca connectors. If i disconnect the rca cables coming from my media server going to the amps, the buzz goes away. If i plug amp input into something else,, like the rca outs on my dvd player the buzz comes back. Any ideas?

Thanks
Philip

 

[Del91574]

Ground loop on some audio equipment most likely, and I'd lean towards possibly the amps, so more detail would need to be known about them.

Any fluorscent fixtures or transformer based loads nearby?

Does it sound like a 60 cycle hum?

 

[pjwinstalls]

closet flourscent fixtures would be in the basement. No transformers. I don't know what a 60 cycle hum sounds like so i couldn't answer that. They are parasound amps plugged into a panamax m7500pro which has a ground isolation feature to deal with ground loops. Doesnt help. The only source to the amps is a Crestron PAd8a audio switcher which i disconnected. The hum went away, but when i plugged another random audio source into the amps like a bluray player, the hum returned. I tried putting the panamax on a different circuit and also tried plugging the amps directly into a different circuit without going through the panamax.... all had the same result.

Thanks

Philip

 

[Del91574]

Without knowing the source, so to speak, I'd start looking at a dirty (noisy) ground or neutral. Easiest way is to start flipping breakers to see what causes it to clean up, then investigate what is on that circuit.

Could also be induction going into the speakers directly, as where the cabling may have been run.

Have you tried a different load?

 

[BraveSirRobbin]

I say it's a 'dirty' appliance, dimmer, etc... that is creating havoc with your AC power lines and can't be filtered via the Panamax. I would start unplugging suspect appliances or dimmers and see if the hum goes away.

 

[tmbrown97]

A couple other things - check the wire you're using to connect; could be a problem with that. Also I believe if the source and amp are on different branch circuits or phases, that can sometimes cause issues - sometimes a power conditioner can be needed... that said, I've been able to make most of my similar problems go away by fixing the cabling to the source.

 

[Del91574]

Also, of interest, YMMV, but I have seen converted PC's or computers cause noisy audio in an audiophile situation as they have a negative reference to ground compared to lots of audio equipment I've worked with.

 

[apostolakisl]

Does your amp hum when a battery powered device is plugged into the rca jacks? Does the volume of the hum go up when you turn the gain on the amp up?

If your amp has an auto shut off feature when it has no input signal and the hum is internal to the amp, then you will get hum even with battery powered devices plugged in and the hum might stay constant when you increase the gain.

Internal amp hum would likely be from a bad capacitor on the power supply board.

 

[pjwinstalls]

I am going to try turning of the breakers to the house and see if one of them makes the buzz go away. There are 120 circuits in the house so it might take a little while. Its not amp itself because all 5 amps have the same problem. I have already tried changing the cable. I also tried connecting everything through the same circuit with and without the Panamax. The induction is possible, but unlikely. I will connect a speaker directly to one of the amps to rule that out.

Will report back on wednesday after i go to the client's house.

Thanks again!

Philip

 

[apostolakisl]

I am going to try turning of the breakers to the house and see if one of them makes the buzz go away. There are 120 circuits in the house so it might take a little while. Its not amp itself because all 5 amps have the same problem. I have already tried changing the cable. I also tried connecting everything through the same circuit with and without the Panamax. The induction is possible, but unlikely. I will connect a speaker directly to one of the amps to rule that out.

Will report back on wednesday after i go to the client's house.

Thanks again!

Philip

It would be easier to start off by turning everything off except the circuits to the audio system and see if the hum goes away. If successful, turn them on in blocks of 20 until the hum returns, then subdivide those 20 into groups of 5, then one at a time when you find the bad group of 5.

Of course, you may find that there is more than one culprit. So once you find one for sure culprit, leave it off and turn the rest back on. If the hum returns, repeat the above process for the remainding circuits. . and so on.

 

[tmbrown97]

5 amps exhibiting the same behavior regardless of source sure seems fishy... make sure in your test that you disconnect every other source other than the one you're testing with.

Also as eluded to above about speaker and battery powered devices... I've noticed many times when running audio off a PC, there's no hum if it's on battery, but once I connect the AC adapter, I get the hum. I've also had certain RCA to 1/8" stereo jack adapters cause issues where others didn't.

 

[Neurorad]

Are the source components and amps all on the same circuit? If racked, you could have 2 circuits in the same rack, so make sure all on the same circuit.

Jensen has a white paper on ground loops, might interest you.

 

[Del91574]

We've always separated the amps from the rack using nylon washers between the face and the rails to help with ground loops, so unsure if you've tried the same in addition to the suggestions above.