Looking for advice with mechanical hum

I’m looking for some advice. I have what I am assuming is transformer hum coming from my audio components. It’s most prominently heard from my DAC (Lampizator Atlantic) though can also be heard from my amp (Classe CAP-2100) as well as a linear PSU (HDPlex).

I would describe the noise as a low pitched buzz or hum. It emanates from the components and is not heard through the speakers. The hum is present in the components even if everything is disconnected apart from the power cord. No hum when powered off. It’s noticeable from the listening spot which is around 3-4 metres away. It doesn’t seem to vary. It is present in the middle of the night also. I have tried different sockets in my house with no changes to the hum. I have not yet tried sockets outside my house but I will in a day or two.

I recently returned the DAC for testing and was assured that when tested there was no audible hum at all.

I have read into this to some degree but electronics is not my field. I have tried 2 different DC blockers (MCRU and ATL Hifi) and neither produced an audible difference. I also use a power conditioner (Audience AR4) but this has no effect on this noise.

Any insights or help here would be greatly appreciated.

Edit: I live in the UK

That sounds like transformer hum.


Thanks - keen for some advice on how I can go about eliminating it.

Are you certain that the hum is emanating from more than one component? Power amps are most common.


There are some outlet type devices designed to address mechanical hum. PS Audio had the Humbuster3.

Humbuster3 is out of production, but can be found on the used market. I’ve included the manual for reference. I had one and sold it, when I was chasing a hum that turned out not to be of a mechanical nature.

Emotiva makes this device (below) to address DC hum…


Sure there might be somes other fixes like Isolation transformers…

Good luck…

Absolutely. DAC and amp, with the DAC having the slightly more prominent hum.

Thanks Robert. Is the humbuster very different to the 2 DC blockers I have already tried? Does it work in the UK? Do you think it is DC on the mains that is the issue? What did you hum turn out to be?

Had a hum in my system turned out to be a light dimmer switch.

If only one component, then the issue could be isolated to only one transformer. But if multiple components, then the issue is not just one transformer. And you probably do have DC offset on the AC causing the hum.


No light dimmer switches in this house. I will try the DAC at a few different buildings though to try and isolate the problem.

If it was DC on the mains Andrew, why didn’t the 2 DC blockers that I tried work?

I could never get it fully tracked down. I changed multichannel power amps, and it stopped. I am not familiar with the products you tried, but mechanical hum is often tied to leaky DC in the AC mains line. Hopefully an EE can join the thread and weigh in.

Lot of people have-had issues with audio hum due to cable tv and boxes

No cable TV here. Standard aerial.

Nothing will drive you madder than a hum in your setup. I’ve taken my system down cable by cable, component by component. It can be an all day job. I still get a little buzz from time to time, and it usually involves my cooling setup (a fan’s power line or one of my cooling components) interfering with something.

Is a dedicated audio circuit something you might consider?

Thanks Robert. I would certainly consider it if it were to work. But if the problem is AC on the mains like others have suggested, then this would be present on the dedicated audio circuit too would it not?

Maybe not. At least this way you are isolating your components from other things in the house (refrigerators, etc) Ultimately, something affecting the whole house (or neighborhood) may still be present. Not overly expensive (here in the US) to setup a dedicated 20 amp breaker and outlet(s). I have my entire system on the 20a, and the cooling system on the nearby 15a circuit. I use Class D amps, so I don’t come close to taxing the 20amp breaker.

Sorry - but no cable manipulations will eliminate MECHANICAL vibration hum generated by transformer!

Then what will :smiley:

A DC blocker or balanced transformer.