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Hum and noises in McCormack amp

I just picked up a used McCormack micro power drive amp. The amp sounds amazing. However the amp puts out some hum when not attached to anything except the speakers. And a little bit of scratchyness in the tweeter.

But then when I attach the front end it hums even more and also makes a noise that sounds like dut..dut dut ....dut dut dut dutdutdut.... dut dut. etc. And a crackly noise a little more in the tweeter.

Its noticible enough to be annoying during quiet passages or when the music is stopped.

When I borrowed an adcom amp it was dead silent. No problems at all. Dead quiet and smooth. Headphones are thes ame. But I just can't seem to get this McCormack to quiet down no matter what I do. Is it possible that it's just old and circuits have gone bad (or whatever else is in there)? Or does it just not like my home? Either way I can't live with it like this. I've had it a week so I'm sure I can still take it back to the store. Although I did tell them the amp sounds amazing and I'd hate to walk in and say "sorry I can't live with it now". Its done this since day one but I thought I could tweak some things to improve it and it's gotten more noticable since I've improved my room and made the room quieter. (and gotten to do more extensive listening).

So do you think that something is just bad or aged and can it be fixed by the store? Or should I just return it and get something else?
kacz
11 responses Add your response
stevemcx
166 posts
 
Hi Kacz -

It is possible that something may be wrong with the amp, but you need to check 2 things first: 1) insert RCA shorting plugs in the amp's inputs. This will tell you if the amp is quiet by itself. If you don't have any shorting plugs, take any cheap set of interconnect cables and stuff aluminum foil in the plugs on one end to connect the center pins and outer grounds together. Plug the other ends into the amp. The amp should be fairly quiet in this case (maybe just a little noise right at the speaker). If there is any obvious noise, there may be a problem. 2) If the amp is quiet with shorted inputs, you probably have a ground loop with everything connected normally. Go to this link to learn all you need to know about fixing ground loops - http://www.altavistaaudio.com/hum.html

Good luck - I hope this fixes the problem.

Happy Holidays,

Steve McCormack
www.SMcAudio.com
joefama
60 posts
 
I had a similar sound from my Pass amp. It turned out to be a defective Michael Wolff cable. Very shotty termination. So check all your cables terminations.
kacz OP
177 posts
 
Hi Mr McCormack

I tried the tin foil deal. And it actually improved a lot. So I went and dug out my one and only cheater plug. I bought it a long time ago to make something fit into an old two prong outlet. Thanks for the link I didn't realize how grounding worked exactly and how to keep it safe as long as components are still connected and grounding out of at least one. I didn't want to mess with removing the ground anywhere before reading that.

I decided to use it on my front end. It's a lot better now. I can only hear it a little bit now if I get close to the speaker. I'm sure I can do some more adjusting. I'll try to work out some more of the loop kinks eventually. But I'm happy because I can listen and enjoy all the music now and the quiet spots.

And I'm happy I can keep the amp. The Micro power drive is a phenomemal amp. The soundstage is amazingly large, deep and defined. And it feels like a lot more than only 50 watts.

(thanks for the help too Joefama always good to go through everything just to be sure).
stevemcx
166 posts
 
Hi Kacz -

I'm glad to hear you were able to solve the problem and keep the amp. I hope it brings you a lot of fine music!

Best regards,

Steve McCormack
albertporter's avatar
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albertporter
4,949 posts
 
Hey Steve, have you heard that new McCormack UDP-1 Deluxe (especially the one with black face plate)?
stevemcx
166 posts
 
Ha! Very funny, Albert. My careful research tells me that the "champagne gold" faceplate sounds best. Now what are you gonna do? ;-)

Steve M
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albertporter
4,949 posts
 
Guess I have to swap it out.

That's unfortunate, because I like the black, it matches the rest of my gear :^).
stevemcx
166 posts
 
Just kidding, Albert. It's actually my custom aerogel / ceramic hybrid faceplate that sound best, and I can have it made in black just for you.
albertporter's avatar
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albertporter
4,949 posts
 
And when you bring out an improved model, mine would show up here at Audiogon with condition listed as "stone" mint.
parnlyp
2 posts
 
I've got the champaign faceplate and I definitely enjoy the warm glow it adds to the environment. Hmmmmmmmmm, sounds pretty good too.
manitunc
795 posts
 
I am looking for a McCormack Micro drive amp, or the headphone amp that also has speaker outputs, the Micro Integrated Drive.
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