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Bad Hum Coming Through Amp, What Happened?

I've been running a Primare I21 amp for over a year now, and have been quite happy with the fact that there is no audible hum that comes through the speakers at any volume output. Out of the blue a couple of weeks ago, a nasty hum has started to emit from the amp through the speakers, audible starting at 20-25% of the volume output and louder as the volume increases. I've changed AC receptacles to a Cryo Hubbell one, I've upgraded my power conditioner, and I've switched the stock power cable to a Magic Power cable (which makes the hum even louder).

I am only using 2 of the 4 inputs on the amp, CD and Line 1 (turntable). The hum only occurs on the inputs that have something plugged in to them, and the hum goes completely silent when switched to an input that doesn't have anything connected to it. I've tried rolling the other components to the other inputs (the hum followed the components), and have tried the upgrade power cable on both of the components (no change). The hum occurs whether the components are off, on, or in standby.

What happened here? How do I make this hum go away? It's driving me crazy! Is there something inside of the amp that can be replaced/upgraded to kill this problem? Thanks in advance!

I posted this in Misc Audio last night, sorry for the double post! I realize now this was a better spot for the question, and I can't seem to figure out how to delete my other post.
maha0098
marakanetz's avatar
marakanetz
5,473 posts
 
Jea48,
It's now I guess too much to ask as changing it back to the original recepticle...
Ehaller might be right but if the problem still persist, I'd suggest to check the unit technically and not to use it until.
rodman99999
6,130 posts
 
DITTO what Almarg said about a possible ground problem. Maybe a loose star ground, or a cold solder joint at a ground point. Definitely not output stage, because it varys with volume control.
maha0098 OP
2 posts
 
Ehaller, I took your advice first figuring that even if it wasn't the problem, it would at least be something to do as good maintenance (similar to tightening the screws on a chassis every so often). The toroidal transformer was tight, but after I took a wrench to it, I got about 2 whole revolutions to get that sucker in as tight as possible. After I turned on the unit, I found out that the buzz had gone down about 20%. Kudos to you for this suggestion!

I still had 80% of the noise to deal with, so up next...

Almarg, I stopped at Target on the way home and picked up a 2-pack of cheat plugs for $1.79, so now I tried adding these to the system. After I plugged the equipment back in and turned on the amp, I heard... SILENCE! Incredibly excited, I turned on the cd player and phono pre-amp, started the volume at zero, and turned it from 0-max on all of the inputs and heard, once again, SILENCE!

All of my woes have been solved, thanks to everyone here for their opinions and help identifying the ground as the problem, and especially to Ehaller and Almarg for their ultimate solutions to the problem!

Now to think that I spent money on a new AC receptacle, power cable, and power conditioner all in an effort to fix this problem, when it took $1.79 to eventually solve it. Oh well, they were upgrades I needed a push to do anyways...

Thanks again, everyone!
rcandpc's avatar
rcandpc
5 posts
 
I have used those ground cheater plugs before & they work great. Does anyone know the downside of using them if any?
rtn1
535 posts
 
I use a piece of electrical or teflon tape to cover the grounding plug on the IEC of the equipment. That way, you are not introducing a cheap cheater plug into the electrical path.
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