[ADUHF]

FYI, I still really have no idea what's goin on here. But I'm sticking with the static charge theory for now.

Between you, the desk (which is non-conductive), and the headphones, you are probably the closest thing to a ground. So when you touch the cable to the desktop, it creates a small circuit between you (the ground) and the desktop (weak static electric field). And that is what is inducing the humming in the headphones.

If this is what's happening, then something in the room is causing the static charge on the desk. And it could be either the amp or it's non-grounded power supply. Or possibly something else. The dryness in the room could also be a contributing factor, which is preventing the electrostatic field on the desktop from dissipating.

I'm not that knowledgeable about things electrical though. So this could all be complete nonsense!

 

[ADUHF]

If the amp/PSU is the source of the electrostatic charge, then touching it may reduce the potential electrical difference between you and the desk enough to effectively break the circuit, and stop the humming.

 

[bigshot]

You also need to consider the possibility of an unreliable witness.

 

[PointyFox]

I'm pretty reliable

 

[bigshot]

Have you gotten a chance to check it in a different location yet?

 

[PointyFox]

Have you gotten a chance to check it in a different location yet?

I've tried it a maximum of about 100 feet away, but I don't really have anywhere else I can bring it.

 

[ADUHF]

Sounds like you are maybe describing mains hum...

Had to look this one up...

https://en.wikipedia.org/wiki/Mains_hum

Hadn't heard of "humbucking" before either.

There are some sample audio files you can try as well in the above article, to see if this is the sound your headphones are making.

 

[PointyFox]

I'm pretty sure it's mains hum, but why my desk/everything on it is conducting it, I have no idea.

 

[bigshot]

I think you live near a large electrical transformer. It’s probably on a pole near your house. But if you can’t check at a different location, I can’t verify that. So I can’t offer you any advice on solving it. It doesn’t sound like it bothers you. So if you can live with it, you’re ok.

 

[PointyFox]

Yeah, I don't need to use it as a DAC for these headphones. Was just really strange how my desk conducts the EMI or whatever.

 

[bigshot]

I think that particular component (or something it’s plugged into is poorly shielded. Wood doesn’t conduct, but the location of the desk might be on top of some EMF hotspot or something.

 

[PointyFox]

It's not the general area, it's when I touch any part of the headphone cable to any part of the desk or items on the desk that it hums. I back it away 1 mm and it stops.

 

[CK Moustache]

@PointyFox

Apart from the issue of the hum also being transmitted when the headphones are unplugged, this sounds like the same problem that I have at my place. Long story short: grounding issue (bad power supply and grounding in my entire home, as it also seems to be the case in yours, as the Koss amp (and your entire audio chain) doesn't seem to be grounded properly). Solution: manual grounding.


To quote the explanation/solution provided by the pro/studio gear manufacturer:

Unfortunately, the customer has a local potential and earthing problem, i.e. the electrical wiring of the house mains. The supplied, unearthed switched-mode power supplies are usually much better than earthed ones because they avoid hum loops. In this case, that is reversed. The secondary side of the power supplies delivers a high-impedance AC voltage that is discharged to earth via the customer's body. This minimal current (of course completely harmless) is then heard in the headphones or in-ear. It really helps to ground the DAC to the current ground potential (heating, water pipe, earthed socket, etc.). Or another earthed device. Screw a cable to the housing and connect it to earth.

Unfortunately I cannot find any photos of your Koss amp's back or rear portion, but connecting a blank wire to one of its screws (if there are any) and the other end of it to a nearby (unpainted) radiator, water line or the likes would most certainly resolve this issue.

 

[bigshot]

I've never heard of wood creating ground loops. Your hand might. Metal might. If your wooden desk is the only place it hums, there is some sort of RF interference in that spot. RF doesn't require contact.

In a modern home, the screw in the middle of your power reciprocal is grounded. If it is a ground issue, that will defuse the noise.

 

[PointyFox]

Unfortunately the amp doesn't have a ground pin. What does require contact then if it's not RF?