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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
mrdecibel
3,067 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
6,740 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. 
listening99 OP
172 posts
 
@jea48 This two-story single family dwelling was constructed in 1986. I have not checked the mains voltage. I imagine this requires a volt meter, which I do not possess. I see a number of them for sale at the Home Depot, which is the closest such facility to my home. Is there a special type I should be using for this test? 
skiroe's avatar
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skiroe
131 posts
 
Hum is my number one bugaboo. I can not stand it .. Often when asking a seller if there is any hum in the unit and being really specific that Im referring to the amp itself they will respond with --oh, its very quiet from the speakers. thereupon now comes a lengthy explanation from me.
I have never held onto anything long that had hum. It often can be in the power supply design but also being directly coming from a transformer Ive been told that it is the plates vibrating. On new transformer in a new unit like the one you got I cant imagine -either p.s. design or cheap transformers .. Im not a tech so cant identify exactly but pass along my experience. I had a custom 2a3 SET built once and it had a hum and the builder used a recycled power transformer ---how old was that thing ? I sent it back,, and he didnt do a thing about it. I sold it. Really had good sound but the hum was so obvious it could be heard from 5 feet away even with music on low. Send it back to Had or at least complain. ruins the experience.

I had a 80's  Sony STJ75 tuner that is well known how black the noise floor is but it had a hum ...  Sent it to ASL   Absolute Sound Labs and he actually had the transformer re-potted .  fixed the hum.     
listening99 OP
172 posts
 
@wolf_garcia My wife thinks I'm being too sensitive about the hum, which doesn't show up at the speakers, as I've already described. Given the sellers description of the "quietest amp he's ever owned" I figured it should be literally dead silent, but now I'm hearing that there may be some small sound issuing from some of these amps, and perhaps the old circuitry of my dwelling is going to place the amp under different forces/conditions than what the seller experienced. As I've also described, it's definitely not impacting the sound, for the system is presenting, along with the speakers, the most beautiful music I've heard in this space. My main concern is longterm difficulty and having just picked up the amp I wanted to address it right away. 
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