Attn: McCormack DNA 0.5 owners

Do you have a 0.5 with a revision c, b, or a? I was just talking with somebody about this. It appears that this sometimes frightening thump has to do with wether or not your particular model has (I believe them to be) input relays.

If you have a Revision of the DNA 0.5, then if that model had the relays and the relays were removed, then the thump appears at startup and/or shutdown.

You should first contact the previous owner to see if he had anybody work on the amp.

Next contact Steve Mc smcaudio.com providing him with the serial number and model to see what he has on file for this particular unit. And of course describe the problem you are experiencing.

-IMO

I have had a mixed bag with the McCormack's I've used. Most of them didn't thump. But I did have one that did. As mentioned above, it may have something to do with the mute relay. Seems the older they get the more likely this is to happen.
Call McCormack and ask. He's a really good guy and shoots straight.

I've never noticed a thump on the 3 DNAs I've owned (0.5s and 1); but then again I usually leave them on. BTW, go for the Rev B or higher; sound is dramatically improved in my system.

Thank you. I will call SMC and ask Steve McCormack what he thinks.

Do you hear the thump the same when shutting down the components in different order? Do you shut off the preamp or source before powering down the amp?

If a Revision would solve the problem, what a bonus! You'll really appreciate what the modded amp does for your system.