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How deadly is transformer hummm...

Hello Folks,

I recently collected a lightly used (less than 50 hours) Dennis Had - Inspire - "Fire-Bottle." Within some few days, I noticed a humm emerging from somewhere within the chassis of the unit. As the unit was sold in "perfect" condition, I found the humm startling. Mind you, I've discovered absolutely no evidence confirming the sound is compromised; I mostly hear the sound within a couple feet of the amp, when the surrounding environment is silent.

This amp truly is a work of art. Nevertheless, I am now dealing with this 'humm' sound. I bought an Emotiva CMX-2 as a way to deal with DC offset, and this has not impacted the situation to any detectable improvement. Perhaps there is a slight improvement, but negligible. What to do?? Should I just relax, shake it off, and assume the amp will live well, or a down-the-road transformer replacement will simply become part of my experience with this amp? Should I put pressure on the seller to "right" the situation? He claimed, as I asked him, that it was the quietest amp he's ever owned. His add boasted that the fire-bottle exceeded amps from Pass Labs, a Cherry Amp, and one other that escapes memory. The seller has presented all of his communication in the manner of friendly professional etiquette. 

Your thoughts are appreciated. 
listening99
invalid
1,207 posts
 
Atmosphere is there any reason why manufacturers don't use nyloc nuts to mount these transformers. They wouldn't come loose with a nyloc nut.
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atmasphere's avatar
atmasphere
11,849 posts
 
Would 248F handle the temperatures within the amp
No worries.
Oh, I will include this marvelous detail about the amp's design: "The transformers are made with grain orientated steel and impregnated with a special anti vibration varnish. Also the chassis of all Inspire products is non-ferrous aluminum."
FWIW, the transformers are 'EI' cores, and all EI cores should be constructed as described above and usually are (often are what is called 'double dipped' in the varnish, which is very helpful in the anti-vibration department). The chassis material will not affect whether a transformer makes noise or not.
Atmosphere is there any reason why manufacturers don't use nyloc nuts to mount these transformers. They wouldn't come loose with a nyloc nut.
Actually they could come loose, since what happens here is that with a enough heating and cooling cycles the varnish can relax a bit. So this might require tightening the end bells down so they don't rattle. Transformers have been made for over 100 years without the need for locking nuts.

mrdecibel
3,065 posts
 
I have an amp in my collection, a Smart Theater Systems TA 242, which is based on a Hafler design, nicely built power supply, toroid transformer, highly biased in class A, roughly 120 X 2. I acquired this years ago from a movie theater updating it’s gear. A wonderful sounding amp. When I use my otr microwave while this amp is powering a system, the transformer of this beast, starts getting pretty loud, even though the microwave is on it’s own circuit. So, there is some truth to what many are saying here about the effects of ac. @listening.....you might want to try moving the amp to other electrical outlets throughout the home, just to see ( hear ) if the transformer still hums loudly. Again, I feel it might be normal. @wolf_garcia , without burning that beautiful face of yours, lol, do you hear the transformer of your Had chassis ? @atmasphere, are the transformers you use, completely silent, when close up ?Again, hum, from a transformer, is typical, and to some extent, normal, when close up to it. As long as it does not interfere with the music listening.
wolf_garcia
6,711 posts
 
There is a sense that the amp is on if you listen very close to the transformers, but any hum is at such a low lever as to be virtually inaudible unless maybe you listened to it with a heat resisting stethoscope. Note that relative to any other amp I've owned, either transistor or tube, there is nearly zero noise even if you put your ear on a driver...the the Firebottle is by far the quietest amp I've ever owned. 
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