Hum can be caused by DC offset, ground loop, simple transformer mechanicals (loose nuts, etc.), or a poorly wound transformer or one that's degraded. Google PS Audio + hum + eliminate for a simple guide. Some hums are easily dealt with, and some can drive you up the wall. Occasionally the only solution is to have a brand new transformer installed.
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.
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.
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@bdgregory the hum is not audible from the speaker drivers. This is a mechanical event, coming from within the chassis. @brownsfan how do I detect tube issues like you describe- microphonics, etc? @stereo5 I always enjoy the humming of my wife, but it seems her tone is at a much higher frequency. I’m running the amp with a DAC and a CD transport... is it ok to unplug the RCA cables from the system, to rule out those components while this tube amp is on? I hear you don’t want to run a tube amp without connections... |
Since this amp employs an EI core power transformer, DC on the line really won't affect it. But if the cores are not secured properly, it can vibrate. The four screws on the power transformer at each corner might simply be loose. Its worth it to see if tightening them makes the transformer quieter. This probably can be done fairly easily. Of course the amp should be unplugged from the wall, and to best do this the bottom cover removed. If any of this sounds at all tricky, take it to a qualified technician. |
I recently had a hum coming from one of my amps. The source was a bad tube. I'd want to rule out other sources of hum before returning the amp. I was advised to check my tubes for unusual microphonics, which I found to be present. I quickly identified the offending tube. Replaced the tube and no more hum. |
I have a Line-Magnetic LM-218ia that emits an audible transformer buzz, which you can definitely hear anytime you are standing by the amp while it's on. I understand from fellow owners that this is quite common to LM amps, and harmless. I guess I assumed it was the price of admission for using an SET amp with massive transformers, and since I can't hear it while listening, never bothered me. As far as this situation, when the seller claimed the amp was the quietest he had owned, I would have assumed he was referring to electronic buzz you can hear from the speakers. I would assume it's within your right to return it if you wish, since this wasn't disclosed, but it also seems to me to possibly be within the normal operating parameters of the amp? |
Sounds like DC offset hum, and the CMX-2 isn't quite doing the job. Send it back. You could try the PS Audio Hum Buster (if you can find one) or DIY as per Nelson Pass https://www.diyaudio.com/forums/solid-state/2080-dc-filter.html |