Lumin Amp: Slight hum from time to time. Maybe due to AC quality?

I own a Lumin Amp and am really very happy with it.
However, one thing keeps puzzling me a bit: During a typical listening session of maybe 4 hours, between 2 and 5 times a humming noise passes through. A bit like a propeller driven airplane was passing a few streets away.
When I happen to be close to the amp when it occurs, I hear it directly from the amp (maybe due to DC coming in from outside), but it goes through the speakers as well. It is not very loud and only audible during quiet phases or pauses in the music.
I live in a 5 story apartment-building in a medium big city, and I am certain that electricity here is not free from foreign influences.

I have a Burmester power conditioner that is supposed to filter out DC and which indicates DC-levels on a meter. However, I do not see a clear correlation betwenn elevated levels of DC and the humming noise …
Anyway, the Burmester should be able to get rid of any DC and according to its own meter it does so in under one second.

Any ideas what I could do to get rid of this noise?
It does not bother me enormously, but it would be even nicer without it.

Best regards,

Elmar

Maybe something is causing a ground loop effect.

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There’s so many things it could be but as @AMT suggests the most likely cause is a ground loop has been created somewhere in your system which becomes more noticeable as a listening session progresses.

There’s an article which describes a few common causes of hum in audio systems…

Understanding what causes Hum will give you some ideas how to start to investigate & resolve the problem.

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Thanks for your input!
Grounding is indeed a very plausible culprit, since I changed the setup of my rack and I think the hum became more audible after this.
I may very well have messed up my grounding during the change …

So that will be my first step of troubleshooting :slight_smile:

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Does it have a toroidal transformer? Another possible cause for hum in toroidals besides DC can be over voltage. That can change throughout the day too. You can check that with a digital multimeter at the wall outlet. If that’s it, complain to your power company who is supposed to deliver power within a given voltage range. Usually they seem to be receptive to this

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Thanks for this idea as well!
Yes - the Lumin does have a toroidal transformer so that might be a possible cause as well.
I will check!

I have a Lumin X1 tethered to a Kinki power amp, the EX-M7, which, unlike the Lumin AMP, is not balanced. Initially, I had a slight hum using the XLR convenience connections. I switched to single-ended (RCA) connections and the hum disappeared. Importantly, though, I have a ground wire between the X1 and the power amp. If I remove it, I get a slight hum. So you might try to ground the Lumin AMP to your streamer or whatever source you are using.

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Is your amp close to your wifi router?
I hear a similar noise using my portable Digital Audio Player if I walk close to my router or my phone is near to it.
This occurs even if the player’s wifi is turned off.

I experienced a similar issue when a Google Home speaker was on the same end table as my headphone amp/streamer. Moving the speaker solved it.
These devices seem to be susceptible to interference from other nearby wifi devices.
Seems unlikely this would be the case for you but thought it was worth mentioning.

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My source is an X1 too (a gorgeous piece of gear!) and I connect it to the Amp via XLR. So probably this should be Ok …
But your post basically points me to the problem of grounding again - so this is really becoming the first task to get in order.
Thanks for your input!

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This is absolutely worth mentioning!
Thanks for this idea. In my case, though, I think it is probably not the cause of the problem since the router is not really close to my listening area.
But still - since this is really easy to check, I will switch off the Wi-Fi part of my network and see if this changes anything.

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This thread is a perfect example of forum etiquette and those willing to give a little assistance. :fist_left::sunglasses: Nice

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:joy: I had similar issues with 2 Echo Studios. It was the Echo Studios causing the issue so back they went to Amazonia. :rofl:

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Please try this:

Or/and, try plugging the X1 and the AMP into the same power strip, to minimize the difference in ground.

Based on forum reports of other brands of DC blockers with other amplifiers, it tends to be a trial and error thing. Some users need to go through different brands to find one that work in their environment. For some users, even if it works, the hum may be minimal but not completely eliminated.

If you’re experiencing a DC offset problem, if you place the ear near the AMP itself, you’ll hear it hum mechanically.

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Thanks very much to everyone here for the valuable input!
Looks like I have a bit of homework to do now :slight_smile:

I would like to start with this right away, but unfortunately I have to go on a trip tomorrow until a few days after Easter. As soon as I come back I will get to work and post the results here.

Thanks again and best regards!

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Another nugget of info. I recently started getting humming from my headphone amp. Audible through the headphones. I grounded the case to a known earth/ground and it all stopped instantly.

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As promised - a short update concerning my humming-problem:

I came back from my trip yesterday morning and got to work right away.
What this means was this:

  • Dismantled everything including the rack.
  • Installed a central ground in the shape of a potential equalization bar.
  • Connected this bar directly to earth and to the power conditioner, amplifier, streamer and its power supply, and to several points of the rack system.

Now I am sitting and listening to music while grinning widely :slight_smile:

It may be wishful thinking or whatever, but I am under the impression that my system sounds quite a bit better than before. That would be a welcome side effect of all this work!

I will keep listening to hear if the main problem has disappeared as well. I would guess yes, since everything seems quieter than before, but since the hum came at irregular intervals there is no real way to say now …

Anyway: For the moment I am really happy!
Thanks again to everybody for the valuable help!

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