McCormack SMC Audio upgrades: how good are they?

11-12-15: Tlcshop
Concerned about tweeter damage more than anything. Also would like to hear the theory behind Steve's removal of the relay

That would be my concern too. There's a reason systems should be turn on and off in the proper sequence.

What;s Steve answer to your concern?

Hello Audiogoners,

I would prefer that my amps turn on-and-off silently but the nature of the design allows for a bit of a turn-on thump, and the amount varies somewhat from one amp to another. I find a small thump acceptable and I would never ship an amp that I thought was doing anything that could cause damage. But I am listening with speakers in the 90dB sensitivity range, and anything higher will make the noise louder. Even so, this should not ever be any problem - your speaker crossover will eliminate any low-frequency energy from getting to the tweeter, and there usually isn't much high-frequency energy in the thump. I realize that a turn-on thump can be annoying, but I have never heard of any damage of any kind being caused.

The new circuit board I use in the DNA amp upgrades no longer requires the mute relay of the original, so it was eliminated. This will not have any consequence at turn-on unless your preamp has some DC offset, and this is unlikely.

Tlcshop, I'm sorry that your turn-on thump is causing concern. If you would like to call me to discuss this, we can see if there is something that might be done to reduce or eliminate the problem.

Best regards,

Steve McCormack
SMc Audio

I had this same thump with a pair of DNA-1 Golds that were connected in a vertical bi-amp configuration to my Vandersteen 3A Sig's. I called Steve to discuss this and he said there shouldn't be any problems. Four years later I had a pair of 0.5's upgraded to Platinum mono-blocks and the Gold's went on their marry way. Still have the Vandy's and yet to have any issue's. I have to admit I was a little concerned every time I turned them on but that subsided with time.
Hope this helps with you situation.

Steve was able to reduce the level of the thump when he performed the upgrades to my signature edition DNA-2 LAE but there is still a little, and it is no problem whatsoever. Fortunately the DNA-2 has a standby circuit so it remains on all the time. My understanding is that many owners of SMc upgraded McCormack amps leave them powered up all the time without consequence.