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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
oldhvymec
5,101 posts
 
No rubber or BRubber or anything  other than silicone.  I have a few noisy transformers that had mechanical hums. Mounting issues. 

Not all silicones are the same. The super HIGH temp. silicone can be conductive. Silicone washers are OK BUT, read below..

Put your hand on top if it FEELS, mechanical, press down, can you dampen the noise? Turn off, UNPLUG, remove the valves, flip it get a 40 watt bulb with pig tails, discharge the caps. Work.

A little dab will do ya!  LOOSEN the securements. don't remove them.
Get a pin applicator (smaller high pressure needle gun) A small grease gun will work. give it a little shot, not more than a BB amount.  .177-.180
at each securement between the two surfaces. Tighten. Let it dry, and try it.

Still hums

Check the valves, PULL and reseat move them (pencil tap test) around see if the noise changes. BAD VALVE.. Have to check them
Valves are good.

Still hums

Make sure the voltage is 120. I have a few Cary designs, they like 120VAC, not LOW. They will hum. Easy to check and or fix. Voltage maintainer or Variac, will really tell the story. Start at 110v slowly go up, the hum will go away at 118-122VAC

Still hums

????? I'm out of low cost easy fixes, go find a repairman. Everything I offered is under 10.00 silicone an High pressure needle gun.

Happy hunting

Regards
listening99 OP
172 posts
 
...and now I have email out to Dennis Had...
mrdecibel
3,067 posts
 
What you purchased, that I recommended, should be fine with temperature, as the mounting area, does not get as warm as other areas of the transformer. Additionally, heat rises. I would like to see a close up of the transformer mounting area, as I am curious to see what atmasphere is speaking of. I have not run into a transformer that could not be isolated, but obviously, I have not seen them all. I am sure Dennis Had will respond, will treat you with professionalism and respect, and, will look to help you. Maybe he will suggest sending him, or his servicer, the amp.
mrdecibel
3,067 posts
 
I believe I found a picture, that allows me to understand what atmasphere was speaking about. The power transformer, seems to be " sunken ", into the chassis, but imo, can still be isolated from the chassis, but likely, not with these that I recommended ( I am sorry ). You can use them on the output transformers, with access through the underside, which is necessary with all transformers, as atmasphere pointed out. I would wait to hear from Mr. Had. I am not surprised you hear the transformer in that thing, close up to the chassis, as it is MASSIVE, for that design. As I said, I hear most power transformers in amplifiers, when close up ( with being careful not to burn myself, as pointed out by wolfie )...lol....I will stay tuned to your progress.
listening99 OP
172 posts
 
Mr. Had has already responded, making an impression and stands firmly by his product. He's given me a test of sorts, to remove all of the tubes in the amp, to then see whether the amp hums. This I will address in the morning... more thereafter... 

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."
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