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MC402 humming.

M

Macx

New Member
Hello

I recently bought an MC402 power amp which i love everything about, except for an audible hum coming from the amp itself.
Before i bought this amp i had the MC252 home for audition and that amp had absolutely no hum at all. Now i know the 402 has a bigger power supply, but i have read that other owners experience no hum from there 402:s. With this in mind i started thinking about my power lines and borrowed a Shunyata power conditioner from my dealer. No luck, the hum was still there. I then tried the PS AUDIO Humbuster III(DC eliminator), still the hum was there.
I have also tried unplugging everything else in the apartment without any luck.
The hum i hear is not loud, but can with complete silence in the room be heard from listening position. In other words about 9-10 feet (3 meters, i live in Sweden) from the amp.
Is this normal or not ?
 
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Are you saying the hum is from the amp and not the speakers? If so, likely transformer hum. Should be covered under warranty.
 
This is not normal. Any transformer will make some noise, the MC402 has potted transformers which will greatly reduce this noise.

Is this a new or used amp? Did the amp need to be modified to operate with the voltage in your area? If so, who modified it. Were any other mods done to the amp?

The hum could be caused by something loose inside the amp, like the nuts and bolts holding the transformers.
 
Hello

First of all thanks for the replies.

I bought the amp new here in Sweden so it has NOT been modified.
I know that all large transformers will make some noise, but how much ????
My previous amp did not make any disturbing noise and that had a big power supply too.
I´m asking cause i don´t want to send it away for repairs just to have the repair shop sending it back, telling me there´s nothing wrong and that the sound i hear is normal.
Acually i don´t really want to send it anywhere at all since it´s so new and the hum has been there from the start. I guess i have to though.
 
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Hi Macx......I've had my 402 for 8 months now and there is no hum at all. I would contact your Mc dealer for service.
 
Hi
Have you connected all your components into one outlet, or?
What else is connected to this walloutlet.

I had same issue when I had my MC275 connected to different outlets that comes from seperated fuse from the fusebox. Had mine at this time with no grounds. Now I have all my components connected to one 16 amp fuse and grounded.
Thanks
 
The components are all in the same outlet and i have nothing else connected there.
I have tried diffrent outlets in my home, but the hum remains. I also tried shutting down every fuse in the fusebox, except for the one that powers the livingroom where the audio system is located and the hum is still there. At that time i also had all lamps and stuff disconnected in the livingroom.

Thanks
 
Hi
Remember that the amp in 240V is 5A if you have 10A fuse. So you don't go over 10A. Just a thought.
 
Macx said:
The components are all in the same outlet and i have nothing else connected there.
I have tried diffrent outlets in my home, but the hum remains. I also tried shutting down every fuse in the fusebox, except for the one that powers the livingroom where the audio system is located and the hum is still there. At that time i also had all lamps and stuff disconnected in the livingroom.

Thanks
Click to expand...

I asume the refrigerator too.
 
The only thing that was running in my apartment when i shut down all the fuses were the amp. It had NO cables att all connected, except for the power cord and the hum was still there. I also tried connecting the PS AUDIO Humbuster when everything else was off, but still HUUUUUMMMMM.
 
Macx said:
I bought the amp new here in Sweden so it has NOT been modified.
I know that all large transformers will make some noise, but how much ????
My previous amp did not make any disturbing noise and that had a big power supply too.
Click to expand...
I would say it's normal to hear some very quiet noise from a MC402 if you are very close to it, I'm talking about having your ear an inch or two away from the amp. If you can hear the noise from 4 feet away or more, I would say this is not normal and it's time to get it in for service.
 
That´s basically how i feel too. I expect some noise, however not from 9-10 feet away. But i do admit, from that distance it has to be absolutely quiet in the room to hear it.
However i feel it should not be audible from that distance at all.

Thanks
 
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One way to be absolutely sure is disconnect everything from teh amp except the speakers. Maek some shorted RCA plugs where the center conductor and sleeve are tied together and plug them into the amp. With shorted inputs and only the speakers connected now you can hear just the amp and decide if it has a hum problem or not.

The hum could be caused by several different issues. My prediction is that it is not the amp. You need to figure it out by isolating it.
 
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