How hot should a McCormack DNA-225 get?


I recently picked up a 6 year old one that was just factory checked. The heat sinks get pretty hot with no signal, and with music at moderate levels (feeding Infinity 8 Kappas, nominally 6 ohms) for half an hour, get almost too hot to touch! I'll call the factory and ask, but thought a voice of user experience could be more "honest." It is on a bottom shelf of a cabinet with open front and large openings in the back. At the time nothing was above it (over 2 feet of air.) The DNA-225 is replacing my 20 year old Adcom GFA-555 which would only get "hot" after a good while of cranking out some tunes.

Also, in a different room, the amp is tripping a 15-amp circuit breaker at turn on. Nothing else is on at the time. The original location may have been on a 20-amp circuit, I'll have to check.

Both these things make me wonder if the factory missed something. Ticket said they just biased some transistors. Any owner expeiences would be greatly appreciated.

Thanks,

Mike
kartracer

Showing 5 responses by stevemcx

Hi Mike -

How hot your DNA-225 gets will depend on several factors, but I suspect that yours is behaving normally. The 225 runs on the warm side normally, assuming it is out in the open. Cabinets will restrict air flow more than you might think, and I feel that this is responsible for yours getting rather warm at idle - but this is not a problem. On the other hand, your Infinity Kappa speakers are known to be a difficult load, and may drop to below 2 Ohms at some point. This is undoubtedly why your amp becomes very hot with use. Under the circumstances, this is still normal behavior, but you might want to think about adding a small, quiet fan to circulate air in your cabinet. You may be surprised at how much cooler the amp will run if you push air into or out of the cabinet. Finally, the DNA-225 does not have a "soft" turn-on circuit, so its current demand at the instant you flip the power switch is quite high. Again, this is usually no problem - but if the circuit branch the amp is on is already loaded-down a bit (with lights or other appliances) or if the circuit breaker is "weak," or if there is a problem with the wiring, this may be enough to trip the breaker. The DNA-225 will not trip the circuit breaker on a normal 15A service, so if the breaker does trip, it may indicate a problem of some kind on that circuit branch.

Best regards,

Steve McCormack
www.SMcAudio.com
Why not? Because they add cost and complexity, and I did not feel it was necessary in the DNA-225. Larger amplifiers like the DNA-500 are a different story, and it definitely must have a soft start circuit.

Best regards,

Steve McCormack
Under equal conditions, the DNA-500 will run cooler than the DNA-225 simply because it has a *lot* more heatsink surface area. Many DNA-500 owners have commented that it only gets warm - never hot.

SM
Hi Mike -

I confess that I am puzzled by the fact that your breaker continues to trip when turning the amp on. The DNA-225 has a fairly large power supply, but tripping circuit breakers has never been more than a rare thing. I can't really imagine anything that could be wrong with the 225 that would 1) cause the breaker to trip, and 2) not show-up in some other obvious way - fuse blowing, amp not working, etc. Did the electrician check your AC system Earth ground? Problems with your power system ground might cause some sort of seemingly unrelated issues like this. I do feel that something unusual must be at work because this is just not a problem normally.

For what it's worth, the "ARC-2" upgrade option does have the effect of being a sort of "soft-start" circuit (even though that is not its intended function). This might eliminate the problem if you decide to have the upgrade work done, but otherwise I don't know what to suggest.

Please give me a call if you want to talk this over.

Best regards,

Steve McCormack
www.SMcAudio.com
760-732-0352
Hello Hi5 -

I presume you are referring to the AC mains fuse for 220-240VAC, and these are always slow-blow. The fuse will read "T5A" where "T" stands for time-delay. FYI, the internal DC rail fuses are 10A fast-blow (F10A).

Best regards,

Steve McCormack
SMc Audio