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McCormack DNA 500 loud hum

So I just picked up a McCormack DNA 500 and the damn thing just hums loudly in one channel when coupled with my cyrus preamp.  I took it in and the tech said it's because the rcas aren't grounded as they enter the same Jensen transformers as the balanced connection, this can result in really bad humming.  He's going to ground them but I just can't believe that I can't run this amp stock with my cyrus preamp?  That preamp shouldn't have any problems with this amp.  Any one have detailed knowledge of these a,ps that can guide me or my technician?

malthuse
hifiman5's avatar
hifiman5
1,832 posts
 
Steve may just walk you through a diagnostic process to discover the real issue.  Good luck.
arcticdeth's avatar
arcticdeth
1,572 posts
 
Call, you will talk with Patrick or Steve himself. amazing people.

best of luck. keep us informed as to what happens!  cheers.
malthuse OP
18 posts
 
I talked to Steve.  I'm amazed a guy like that just answers the phone!  He had some suggestions around my system that is quite complicated.  He said it might be blown fuses.  Anyway, I checked, the fuses are fine.  My tech suggested getting rca to xlr cables.  I got a specific kind he recommended, something to do with pins that I didn't follow.  Anyway, long and short, using rcas is catastrophically noisy, using the xlr inputs with xlr to rca cables and the amp is up and running and sounding great.
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