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Help? Possible problem with my McCormack dna-125.

I recently bought a McCormack dna-125 here on Audiogon and I enjoy its sound very much. However, on the weekend when I crank it up (0.0, equal to 12 o'clock on a dial) for awhile the amp has twice just stopped abruptly in mid song after about 30 minutes at this volume. The led goes out so I assume the power is interrupted so I immediately turn it off. The next day when I turn it on it plays as if nothing ever happened. Because it only does this at higher than normal listening volume I am thinking a clixon fuse or something like that is knocking out the power. I'm thinking this may be heat related but I often leave the amp on for many hours at slightly lower volumes (15.0-10.0, 10-11 o'clock) without issue. I crank it up a little higher once a week or so and this doesn't always happen. Has anyone had similar problems with this amp and if so, what did you do to remedy it?

McCormack dna-125
McCormack rld-1
Esoteric p-700
Parasound t-3
Unity Audio Cerious 7
Pioneer pl-530
Entech nc205.2
APC h-15
Cerious Technologies interconnects
Home made silver-clad copper wire speaker cables
silversurfer0116
5 responses Add your response
stevemcx
166 posts
 
The RLD-1 volume display reads actual attenuation in dB, so 0.0 is unity gain (output voltage equals input). Given that 2VRMS is industry standard for max output level on most CD players and the input sensitivity for the DNA-125 is 1V for full output, this would suggest that you could be well into clipping, at least on peaks. So it is possible that you might be triggering the thermal cutoff circuit after playing at this level for a while. The thermal switch is set so that it cuts off around 80 degrees C, which is extremely hot - enough to burn you quickly if you touch the heatsinks. It should be easy to check for this by monitoring the heat sink temperature as you crank-up the volume, but it seems most likely that this is what's happening.

The DNA-125 has plenty of power for most speakers in most situations (and also runs fairly cool typically), but it may be that you are pushing it to its limit.

Best regards,

Steve McCormack
SMc Audio
silversurfer0116 OP
15 posts
 
Hey Stereo5. I checked out your system and I couldn't help but notice that your Odyssey speakers look nearly identical to my Unity Audio speakers. Same size and speaker configuration. Different wood but nice. I am going to try your granite trick since my set up is similar. I got into the higher end gear recently when a friend put me in touch with the owner of Cerious Technologies (formerly Unity Audio). I couldn't bring myself to spend the coin on his current speaker offerings which I will probably regret as my friend has a set and they are some of the best speakers you will ever hear. The guy did however make me a deal on some Unity Audio speakers along with some electronics, power cord, interconnects, etc. These speakers are actually custom prototypes very similar to Unity Audio Cerious 7 speakers although they are a little newer with an upgraded crossover and other little extras. He used them for a couple of years at the CES show. Whatever the case, they sound great and sad to say I am hooked; my bank account doomed forever.
silversurfer0116 OP
15 posts
 
Thanks for the reply. I would not say ear bleeding loud. I would say loud as in you would have to double the volume of your voice to have a conversation while the music is playing loud. I was playing Stevie Ray Vaughn's greatest hits the last time this happened. Good tunes to play loud. I may be wrong but I would not think the amp would clip at the 12 o'clock setting with the speakers I have which are fairly efficient. I am more inclined to think it was a thermal issue although I play it for hours sometimes at 11 o'clock like I did this morning while I painted a room. The amp is in a large cabinet open to the front with 6" of air above the amp. I'm going to move it to a totally open area without the cabinet and try it there. Hopefully this will clear up the issue since I really like the amp's sound and build quality.
sfstereo
215 posts
 
Thermal protection is turning on to prevent damage.
stereo5's avatar
stereo5
6,250 posts
 
My guess is that you are clipping the amp and its protection circuitry shuts the amp down to prevent it from getting damaged. Is the sound ear bleeding loud when this happens?
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