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?

Before you throw money at it, the source of DC might be the house.
Granted that there might be DC in electrical network, but there it has never cause any amp to hum this much. I've live in this house for 10+ years. The D200 was connected via the same AC cords to the same outlets for 1+ year. I am trying to determine if there's a problem with the M250. Maybe the transformer came loose during shipping? or there's a faulty cap? It was a very loud mechanical hum that made me look outside the window for a garbage truck or motocycle.
boths amps acting up at the same time?
Funny coincidence, I've been having the same (or a similar) symptom with my D200 when it's plugged into a PS Audio PP Premier. But it sounds great with the Premier and is otherwise operating perfectly.
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.
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.
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.
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.
Psjulian, Thanks for the confirmation. I hooked up the D200 again and it had no hum unless I put my ear on the amp.
Good Luck!
i used Gamut M250 mklll about two years,every day 4to6hours.nothing happen like that,so i suggest send back the amp to dealer.
I ould like to have informations about the sonic differences between the D200 mkIII and the M250 mkIII.
I actually own a D200 mkIII with my Tannoy GRF and I'm very pleased with it.
I have the opportunity to buy M250 mkIII amps but is it a good idea ?
My other solution would be a class A amplifier, like Pass XA.5 series.
Thanks a lot for your advices.
I tried Pass (X350?) with my Sonus Faber Stradivari. It wasn't for me. I love the Gamut sound. In spite of their sensitivity ratings, the Strads needed that much power to sing. Better channel separation is NICE! Save the technical issue at hand, which will be worked out eventually, it was well worth the upgrade. I wouldn't go back to the D200 as long as I have the Strads.
Thanks for your answer.
The big differences between the D200 and M250 are more power and channel separation ? No big difference in sound, for example bass control or extension ?

What was the problem with the Pass : could you explain a bit more ?
M250 of course bass control and extension is better than D200,also micro dynamic is better than D200.
Thanks for your answer.
SO, the M250 is worth the upgrade even if my speakers are easy to drive : Tannoy GRF ?
I can have a pair of M250 for a fair price.
I never use and listen Tannoy GRF,so i don't know.but i think if you can have a M250 mklll for a good price,i think it's worth because you don't need change amp on future.M250 mklll can drive most of speaker in the world.
Do you have compared the Gamut with Pass amps, like the X350.5 or the new XA.5 series ?
I didn't compare.but both amp is good.and if you buy PASS amp,you need to concern the impedence because it's low.
The nwer Pass amps have correct input impedance.
And my source has a very low output impedance : less than 50 Ohms.
if you love PASS sound,just go ahead,trust your ears
Hi Nico_g. Nothing wrong with PASS, but in my system, I just love the Gamut sound. I am using tube preamp with the Gamut. The PASS, even with paired with PASS pre-amp, sounded like ordinary electronics. Yes, the M250 is better than the D200 in all areas. The Strads have 2 12" woofers which need more power. I don't know anything about the Tannoy GRF. Like Samtse said, M250s are a keeper.
Sorry to side track a bit.. but having owned the Strads previously, I believed those twin woofers are not 12". More like 10"s I think?
I like the GamuT a lot, but, you know, Pass is very good too : I talk about the Call A models like the XA100.5.
I'm sure that the Class AB designs like the X350.5 aren't as good with easy to drive speakers like mine.
The Tannoy GRF are 95db/W/m with 15" woofers and around 8 Ohms impedance.
Hi Ping,i also using tube pre(aesthetix) with my GamuT amp.which tube pre are using now?
my GamuT D200 is directly connected to my dCS Elgar Plus, no preamp for me.
Samtse, I am using First Sound Presence Deluxe 4.0 Mk II. I am hoping to upgrade their higher end 3 box preamp.
Back to the OP Question about the hum. I once had a large amp, big transformer, large caps, etc. . . That's a lot of reserve to energize. I know this Q is old.

But I would occassionally run into a similar problem, turns out during the hottest summer days. Called the amp mfg. thinking it was a cap or transformer. Discussed several times and eventually concluded it was a combination of a lack of power supply in my house and the very hot and humid summer days - causing everybody in town to run their ACs. Lot's of draw which seemed to result in the power reserves having a tough time staying or getting fully charged up.

Power usage in neighborhoods is up in the mornings - curling irons, coffee pots, hot water heaters, hair dryers - all energy consuming devices. Perhaps a correlation?
When the mains power waveform is distorted ( sine wave with flattened top) from heavy loading in the local grid, any transformer will hum.
It is called magnetostriction, the iron core actually changes shape, vibrating internally. Warming up may reduce the noise.

well designed toroid transformers for Audio use have about 5% magnetic headroom. The ring shaped core is wound from a long band of grain oriented silicon steel, and cast in epoxy to prevent buzz. The finished toroid xformers are also vacuum impregnated and baked to prevent loose windings buzzing.