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 1 response by bmotorcycle

Getting on this topic late so maybe you have looked at or have already been advised of this. Since you have a dedicated line to your equipment you probably don't have this, but on the newer houses, I guess for newer codes, some of the circuit breakers are now equipped with a quicker shut off. Even though they are rated at the 15-20 amp constant load they will flip when seeing a real quick spike, this especially holds true in the high lightning storm areas. I have my listening room on a dedicated circuit line and when I had my electrician install my line he told me he had to use this type of breaker to stay within code, if/when I wanted to change it he would supply me with the breaker but would not install so as not to jeopardize his licence.

I have two amps that are doing just what you are complaining about, a vintage Krell KSA 100 and a highly modified little 2A3 SET amp. The krell I can understand why it is tripping the circuit, it has no protection circuit and goes right to the very large capacitors. The 2A3 amp has had a lot of bi-pass capacitors added to the power supple as well as in the signal path. When it is turned on it either trips the breaker or takes out one of its fuses. Issue 2, has you amp been modified? My solution was to have on outboard slow start for all of my amps and the problem was solved. I started with a variac but it degraded the sound so I modified a Welborne filter with a 3 step slow start circuit, problem solved. I leave the amps switch turned on all the time (saves the amps switch) flip the first switch on the out board filter wait about 10 seconds, flip the second switch wait for the bias to build (2A3 amp) (about 30 seconds) flip the third switch which than is direct and enjoy. This has worked for me for the past 4 years, a little trouble but well worth the effort...............

Again, if this has already been suggested sorry for the redundancy......Bob