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Gamut M250 MK3

I got a pair of Gamut M250 Mk3 mono-blocks that went in place of a D200 mk3. They were installed yesterday, and worked fine for a day. This morning I turned on the amps to warm up. A bit later I went back to the listening room and heard a very loud hum. First I looked out the window for a garbage truck; then put my ears against the speakers. Nothing there. It was coming from the amps. Power-cycle of both amps confirmed that both were making that noise, though one was louder than the other. About 10 minutes later the noise was gone. I have a feeling that this might be one of those intermittent problems that's difficult to track down, but I do want to get to the bottom of it while they're in warranty. To other owners of the M250, have you ever experience such a problem?
ping2357
ping2357 OP
10 posts
 
yes both amps made that noise, though one was louder. it's been 2 days since that incident. each morning when i turn on the amps, i could hear the same kind of hum, but at a very low level. i had to be right next to the racks to hear it. as the amps warmed up the noise went away. Other than that, the amps sound great. The Strads are much happier with the added power.
ping2357 OP
10 posts
 
shortly after my last post, the amps started making that loud noise again, though not as loud as last friday morning. i put a sound level meter on top of the amps. it measured a constant 61db on one, 59db on another. it sounds like the transformers. the noise eventually went away. so far the noise varies with amount of warm up time.
psjulian
99 posts
 
Send them back while still under warranty. I'm using a DI-150 integrated and have NO hum unless you put your ear on the amp and then it's just a typical transformer sound.
ping2357 OP
10 posts
 
I hate to send them back, but I may have to do that. When I was listening to the cello suite late last night, in between the notes I could hear the transformer hum. My listening position was 12+' away. Sound meter on top of the mono-block chassis measured 55db. On top of other components, it measured nothing(<50db). I turned off the system in disgust.
ping2357 OP
10 posts
 
Psjulian, Thanks for the confirmation. I hooked up the D200 again and it had no hum unless I put my ear on the amp.
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