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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
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. 
listening99 OP
172 posts
 
Would this do the job?

https://www.homedepot.com/p/Commercial-Electric-110-220-Volt-AC-DC-Voltage-Tester-VT-8900R/202520892...
skiroe's avatar
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skiroe
131 posts
 
As long as your home AC is within reasonable spec I dont think it would be the cause of tranny hum. The type of hum from home AC would likely be most evident at the speaker. Although good to check your AC voltage although that tool is just to check the circuit and wont give you an actual  reading.  I suspect that the 110 volt will light up even if your at 120 or so--probably even at 130 ...because at times that is what home ac is.   Thats what it was at my previous home and I had
utility company come over and even he had to comment . well the AC is a bit high here and he went to the sub station to lower it for the neighborhood I guess.

Its in your amp for any number of reasons. As Atmasphere mentioned be sure to check the bolt down for the PT and put rubber washer in there as well if you can.
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