2. amps-preamps
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Hum in speakers, and suggestions for stopping it

Hi, everyone.

Any success stories in scenarios similar to mine, described below? Grounding boxes? Outlet upgrades? Gadgets like the Morely Hum Exterminator (née Ebtech Hum X)? I’m looking for a non-invasive solution (e.g., not getting a dedicated line into the room).

The situation: I had each of my PS Audio M700 amplifiers plugged in to a Stellar PowerPlant 3. The system sounded great, but I knew I'd likely get better sound with the M700s in the wall outlet. I made the switch and there was a huge improvement -- so I want to keep this configuration.

However, there's now a hum in the speakers. Given that there was no hum with the M700s in the PowerPlant 3, I think it's safe to assume the problem is the wall outlet. I can't hear the hum 99.5 percent of the time when music's playing, but ... well, you know.

"My" electrician came out yesterday and said doing a dedicated line to the outlet would entail demolition and/or other options that aren't feasible right now.

Thanks much!

speakeasy412
clio09
3,355 posts
 

Are both amps plugged into the same outlet? If so and if you can get an extension cord and plug one amp into another outlet, preferably one on another circuit. See if that cures anything. The outlet tester and cheater plug are also worth looking into for troubleshooting.

 

erik_squires
16,056 posts
 

Are your amps and other equipment now on different outlets?

woodman2
9 posts
 

Do you have the amps next to the speakers? I had a Velodyne sub next to one speaker and a hum from that speaker even when the system was off. I moved the sub and problem was gone.

Phil

carlsbad2's avatar
carlsbad2
1,602 posts
 

Your best bet is to get plugged back into a PSA PP.  The PP3 is indeed small for 2 x 350W amps.  Try plugging one into the wall and one into the PP3.  One amp should be good in a PP3, if so, you can find another PP3.  Or just upgrade to a PP10 or PP12.  I have the PP10 and swear by it.

Jerry

zazouswing
148 posts
 

Have you tried unplugging everything in the shared circuit to see if there is a specific culprit? Put a meter mic on the speaker and walk around unplugging stuff with a stopwatch. If the hum exists in the wall but not through the power plant, my would be there is noise on the neutral or ground and it’s finding the biggest transformer tap in the whole house circuit to land on. The benefit of a dedicated circuit - since all circuit neutrals come together in the panel anyway, is really the ground between the panel neutral/ground and earth / waterline. You need to get that noise to have a preference to go elsewhere. Cheater plugs - and I believe hum eliminators - are basically lifting the ground. If you can find the problem, you could put a cheater plug there and not at your amp. 
 

To me, a cheater plug is a simple test. I’ve been lucky in my house that I haven’t had this issue - but I have chased it through hospital construction sites before. I actually had a project where we solved the problem by installing a large, dummy load transformer in an IT closet. The noise on the line preferred that load to the IT switches. If you have a spare amp lying around that has a larger transformer than your amps - try plugging that into the same circuit. 

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