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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
almarg's avatar
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almarg
9,670 posts
 
See my response to your other post.

I wouldn't think the problem is in the output stages, because of the sensitivity to volume control setting and source selection, even when the source components are turned off and sending no signal into the amplifier. It's most likely a grounding problem (for which I suggested some things to try), or an internal problem in the input selection or other front end circuitry of the amplifier.

Regards,
-- Al
ehaller
98 posts
 
I found that tightening the screws or nuts on toroidal transformers stopped a hum issue I had. I don't know what transformers you have but open up the amp and look. It's worth a try.
rleff
1,065 posts
 
I agree with Al's suggestions;has any electrial devices been added somewhere in the home that might been sharing the ac lines powering those amps or are you on dedicated
power?
jea48
4,425 posts
 
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.
Ground loop hum as a rule is volume independent. Therefore jmho your problem is not related to a ground loop problem.

The hum occurs whether the components are off, on, or in standby.
Just for the hell of it unplug the source component from the power outlet. Is the hum still present?

You said everything was fine up to about two weeks ago.... I would reset everything thing with your audio system back to the way it was before the problem started.

I would also try plugging all the associated equipment directly into the wall power. Do not use the power conditioner. in fact unplug the power conditioner from the wall outlet.

Primare I21
.
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.
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