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The faintest hum from Michi X3 through speakers

axiomofchoice

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Jun 24, 2024
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I know this is well worn as a general topic...but here goes...

I purchased a used Michi X3 integrated amp about a month ago, and only recently noticed a faint hum or buzz coming through the speakers. One speaker hums a little louder than the other -- I can just hear the louder one from like 2 feet away, while the other I can only hear with my ears right on the speaker. It seems to be the amp itself, as I unplugged everything connected to the amp (besides speakers and power) and it still hums (that rules out ground loops), and if I swap the speaker cables on the back of the amp, the humming swaps speakers (that rules out speaker cables and speakers). I'm plugging power directly into the wall, and have tried different outlets on different circuits (including a dedicated 20amp circuit), and different power cables --- same effect. The hum is at a constant volume, regardless of the volume setting on the amp. It stays the same if I switch inputs. The speakers are KEF Q11 Meta (not super sensitive -- 89db rating).

I otherwise am happy with the amp, and since it took me over a month to even notice this, I can almost certainly live with this -- I can't hear it at all from my usual listening position, at least given the background noise in my listening space, even when the house is at its most quiet.

This is truly a "first world" problem, I know...
I'm really just wondering what causes this type of thing. I mean, I think my testing clearly implicates the amp (do you agree?), and an amp like this should not be doing this. Maybe the amp is faulty or because I bought it used something is wearing out? Hopefully the issue will not get any worse (and become an actual problem).

Any thoughts? Thanks! ...and happy new year!!
 
and if I swap the speaker cables on the back of the amp, the humming swaps speakers (that rules out speaker cables and speakers)
This to me is the most telling thing. I’m not even close to the expert 95% of people on this forum are, but based on the above it would seem you may have a bad channel. It likely is a simple fix for someone who knows what they’re doing. but others here will know more.
 
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On the other hand - you can't hear it at the listening position. (unless that is 2ft from the speaker)

So I would stop worrying about it. You can't return because you purchased used, and it is not worth spending money on fixing something you can't hear.
 
@DMill and @antcollinet ...thanks for your comments. I bought it from The Music Room, and they have a 90 return window for defective used items. So I could try to return it, but it hardly seems worth it (it would be a pretty big hassle to do so, not the least of which is this thing is sooo heavy, just repacking it would be a major project...and I'm not 100% sure they would see this as a "defect").

I know it's kind of a non-problem...just wanted to understand what is going on...
 
One final thought, if you haven’t already, is make sure all the devices you have are not only unplugged, but turned off. I’ve read about people who have had something as simple as a fluorescent light nearby causing issue. Though I have not personally had issues like this. I do understand you wanting it perfect. It’s not a cheap amp even used. But agree that if you can’t hear it normally it’s really not a big issue.
 
@GiBo61 Thanks for that...yes, I've seen that review...so my expectations were pretty high...oh well :-( . I have much bigger problems to worry about, so worrying about little things like this is nice distraction :)
 
@GiBo61 Thanks for that...yes, I've seen that review...so my expectations were pretty high...oh well :-( . I have much bigger problems to worry about, so worrying about little things like this is nice distraction :)
Hmm ... "nice distraction" ...it is broken amplifier. Send it back.
 
The signal-to-noise ratio as measured by Hi-Fi News wasn't stellar ("below average" at 80 dB, A-weighted). Some audible hiss at close distance shouldn't be surprising. However, the review sample had hiss, not hum/buzz.

Michi x3.png
 
Any hum through speakers from a solid state amp is abnormal and indicates a problem.

I had this same issue with an AR amp, turned out to be a dodgy capacitor. Easy fix - according to my EE pal, anyway, I'd have had no idea.

Get it checked out and sorted. Expensive amp, well worth the cost of repair.
 
@NTK Thanks. Definitely not hiss. Sounds much more like this: https://blogs.qsc.com/app/uploads/sites/3/2022/11/60-cycle-hum-27405.mp3
That being said, it's coming from the combined midrange/tweeter of the kef, so it's not really 60hz (and it is very faint!).
@Mart68 Thanks. TMR Audio might agree to get it fixed if I press them, as I'm in the 90 day window for defective products. I just have to figure out if I want to do this if I can't hear it in normal use...unless it's something that could progress.
 
@Mart68 Thanks. TMR Audio might agree to get it fixed if I press them, as I'm in the 90 day window for defective products. I just have to figure out if I want to do this if I can't hear it in normal use...unless it's something that could progress.
IMHO, even if it does not progress, it may become an increasing annoyance as you will randomly come to notice it over time. I had an AR preamp that was quite noisy only within two feet of the speaker but I could not live with the knowledge of that noise, even though I heard it only when passing near the speaker. It was unrepairable and I sold it to another person with full disclosure of my experience. I believe that he, too, is moving on from it.

But that's me..................
 
@Kal Rubinson When I was a teenager (a long time ago), I took over my parents "console stereo". I thought it sounded pretty great...but it definitely always hummed, and I never worried about it.
 
@Kal Rubinson @Mart68 quick technical question that I meant to ask. The hum is coming out of the kef combined tweeter/midrange. Not sure if the exact crossover, but I’m sure it’s way above 100hz. So how can I be hearing a 60 or 120hz hum in the first place?
 
@Kal Rubinson I see. Thanks. But the interwebs say that it should be either 60 or 120, at least if it’s either a ground loop or bad cap. What would cause wide band?
 
at least if it’s either a ground loop
Its not a ground loop if it happens with only power and speakers connected. In any case, a ground loop is not an amp fault.
 
@antcollinet true. But as suggested elsewhere in this thread, it could be a failing capacitor. But would that be consistent with a hum through the midrange driver? I don’t hear anything from the bass drivers.
 
Just take it back, and get something different. Any hum at all even very quiet is unacceptable. Plenty more fish in the sea.
 
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