Axiom Home Page Forums General Discussion Technical Questions Amplifier hum

Hello all. Just need some advice on a possible DC offset situation. I have 2 separate amps in my system. One amp is connected to my front LFR 1100's and VP180HP. The other is connected to 4 QS8's. I have a hum coming from both amps that is audible when turned on and without any source being played. Has anyone had this problem and what was your fiix? Emotiva has an inexpensive device,CMX-2, that may help. Any thoughts would be appreciated.

Welcome JBrad,
Sounds like you may have a ground loop hum. Does it happen when only one amp is on? What other equipment is connected? Best to try and identify and eliminate the voltage differential at the source if possible and could be the cheapest solution as well. Test one component then one connection at a time then figure how best to deal with it. Why spend $120 on a CMX-2 when it may not be needed at all?

I had this issue a long time ago and it turned out to be my coaxial cable from my cable provider. With a $2 cable ground part to my main house ground the issue was gone.

Cheers,

Thanks Dan. I don't believe it's a ground loop problem as I've tried everything with the same plug in. Then again I may be wrong. I have 4 dedicated 15 amp circuits to the breaker box and 1 20 amp. I have tested 1 component at a time and the hum may be a little less noticable with only my front amp connected. I have an Arcam BDP 300, LFR100 DSP, PS3, SVSSB13 sub, Arcam P777 amp, Arcam P1000 amp, Marantz 7701 pre/pro, and a 60" plasma TV in the loop. If the hum was coming from the speakers instead of the amps themselves would that be a ground loop issue? Thanks again.. Also, I know power conditioners don't do jack with these problems but I have 3 in the loop as well.

Temporarily install a cheater plug to see if the problem goes away.

Thanks Mojo. The cheater plug you mean is 2 prong into the wall and 3 to the component?

Cheater plug image --- https://upload.wikimedia.org/wikipedia/c...plug_edited.jpg

Thanks again Mojo.

Also try progressively disconnecting each source at the receptacle AND its downstream connection (eg. Receiver).

You'll hear ground loop hum in your speakers and not electronic components.

Have done Mojo. I think I'll buy the Emotiva tweak. If it doesn't work I'm only out the return shipping. It might be something I want in my loop anyway. I can hear something from my LED pot lights...

How old is your home. You may want a respected electrician to inspect your outside ground rod. I lived in an old house and i solved my hum issue's by plugging an extension cord into a receptacle down the hall on a different circuit to run some of my equipment along with a cheater plug. Some old houses have some messed up wiring issues. As stated before, cable vision can cause issue's you may want to t install a baluns on your cable.

When I moved in to my present home, after many months of investigation including setting up power quality waveform recorders, I traced blowing bulbs and hum to what I believed to be a insulation break-down on the pole-mounted distribution transformer windings. Sure enough the local utility checked out the transformer and promptly replaced it.

Thanks Socketman. My wife and I built our new home on our rural property about 13 km from a city in Alberta. Moved in June last year so the wiring is new. No TV cable connection, just an Xplorenet connection (think satellite) to a wireless router. We did have a new power pole provided by the utilty company, Mojo, so I'll check what's happening there. I'm not new to this forum but I created a new user name due to a new email. I've read a lot of posts by you guys and thanks yet again for your advice.
Brad

Enmax in Calgary and AltaLink have both encountered ground rod corrosion from the acidic soil in Alberta. Your installation is new however so I wouldn't expect any grounding issues. It's certainly worth checking though.

An input transformer would help. Equi=Core balanced power supply.

I had no end of issues with hum and certain components. you need to try unplugging everything else from the wall. I was getting a hum from a faulty power brick that my media center pc was using.

silly part was it wasn't even plugged into the pre-amp. It worked fine with my cheep pioneer receiver