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Power amp humming? Is this normal?


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Hi everyone,

 

I received a new Anthem MCA-20 power amp today. The power amp is aimed to take the load of my Studio 100s off my MRX-710 so it has an easier time doing the remaining  5 channels of my sound system.

 

Being excited, I really wanted to have a serious listening session. So I unwrapped it, and started to connect it up. I turn it on, and a droning 50Hz hum started. There was no signal, but this hum was irritating to say the least. So then I put it onto my TV cabinet, and boy did it get worse. Now I don't put too much stock in specifications, but any benefit of having a low THD would be utterly eclipsed by the drone, even in my normal listening levels. Loud movies.. well that's an entirely different matter.

 

The power-amp's chassis vibrates when on. I can feel it with my hand.

 

Does anyone else have an MCA-20 (or 30/50). Do they have this audible drone? I'm trying to figure out if it's normal for this model, if I have a defective unit, or if there's some environmental factors at play. The only thing I can say for sure is that my MRX-710 is dead silent.

 

Anyway, when listening to things at louder volumes, I must say that the power amp has really given life to studio 100s. They may be efficient, but there really is an advantage to "Head room!".

 

Hope you're all having fun!

Hamish.

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Hi all,

 

After checking the cables, and disconnecting everything but the power cord, the unit still hummed. So I called the retailer and they said that it's likely a defective unit. The retailer didn't have any others, and I'd had some extremely negative experiences with their courier service of late (TNT) so they put me in direct contact with their importer, Audio Active. Wow was their service helpful, efficient, and honest. I had a new unit at my door the following morning, I compared the two, noticed there was a significant improvement, and arranged to send the faulty one back. No problems whatsoever. Startrack is much better in Canberra than TNT.

 

The fact that (with no input connections whatsoever) that both hum to a greater or lesser extent makes me think that there's something else at play. The hum is still there, but it's now a very subtle background noise. If I put some more damping material below the feet of the amp, I'm sure it'd be close to silent, but I'd like to address the problem rather than deal with the symptoms. To that end:

 

I have some new power cables coming in the mail, and I'll be borrowing my friends isotek sigmas power conditioner while he's abroad to see if that helps as well. Apparently that made a big difference too. I'll post my findings when I get everything sorted.

 

Thanks for the advice, I really appreciate it.

Hamish.

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I got 3 versions of the same manufacturer's power amp 'til I got a quiet one - it was toroidal mech hum. Upgrades each time & wound up with a higher quality amp, as well as hum-less! Yeh, it cost more!

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