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

Showing 8 responses by gruggn

Can it be the relay in the protection circuit that is failing? Sorry if Im hassling but i really want it to work.
I´ve now talked to the people at SMCAUDIO and they said that I should measure the DC offset at the speaker terminals and if after turn on it goes down to zero there was nothing wrong.
Because of electrical bills and the risk of fire, if something is wrong I don´t want to be at work when it collapse. So to the question(s), what if there is a high enough DC offset to be worried about, what may be the cause, and what causes the thumps? If there is a protection crcuit wouldn´t it stop the DC from reaching the speakers? I thought of the idea of installing a relay but I want to fix the problem at the source.
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,

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.
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
So maybe the protection circuit is only "active" if the DC goes high enough? Well that makes sens in a way, that is probably why it is called an "advanced protection circuit".

I guess I shouldn´t worry, after all, it sounds like heaven through my speakers.

Thanks again,

Fredrik