2. amps-preamps
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McCormack DNA 0.5 Deluxe thumps turning on/off

Hi guys.

I have an McCormack DNA 0.5 that thumps when turning on/off. I recently bought it used and love the sound and all but I cant seem to look past the thumps, i´ve had amps that have done this before but this amp play in total different league. I know the deal about turning the power amp on last when starting and then last when done listening.

I have also plugged it in without any speaker or line cables connected and put a multimeter at the binding post and it picks up a DC current, same for both channels. Note, this happens only when turning on/off and overall performance other than this is excellent.

I also noted that if I have, say my cdp playing and the volume up a little bit you can hear the relay clicking and also a for a fraction of a second there is music playing. I have yet to come to a conclusion on what the problem is and have contacted Steve himself about it, but as an unpatient man I want things done in short notice.

So I would be happy if someone could help me or at least figure out what the problem might be.

Thank you
Fredrik
gruggn
jebe1
75 posts
 
I have a DNA-0.5 and a DNA-0.5 Deluxe and my friend has a DNA-0.5 Deluxe and they all "thump" when you turn it on. It is my understanding that this is related to the power supply caps charging up, but perhaps Steve McCormack can post and give more insight.

When you turn on your amp, does the front LED turn from yellow to green after about 15 seconds? If not, that would indicate a problem with the amp.

BTW, I usually keep the amp powered-up as it sounds better after being on for 24 hours.
gruggn OP
8 posts
 
Okay and this as never damaged any of your loudspeakers? As I said before I've had amps that have done but maybe I am paranoid. Ah well I will measure the DC offset and see if something's wrong.

Thanks for the replies
jebe1
75 posts
 
Gruggn,

No, the "thump" has never damaged my loudspeakers. I also have an Audio Refinement integrated amplifier that gives a loud "Pop" when you turn it on.

I don't know what loudness or duration of the "thump" would indicate a problem with the amp.
gruggn OP
8 posts
 
Jebe1,

Well that is certainly reassuring, I always thought it would damage my speakers but time will tell and until I get that multimeter in my hands I wont know.
gruggn OP
8 posts
 
Okay and this as never damaged any of your loudspeakers? As I said before I've had amps that have done but maybe I am paranoid. Ah well I will measure the DC offset and see if something's wrong.

Thanks for the replies
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