Strange ground problem

[regiregi22]

I have made some microphones from a Linkwitz design, and while they sound pretty good when laid on a mic stand, I get a very annoying humming background noise when I use them near myself.

It's a very strange behaviour, the closer I get to them, the more EMI/ground related hum noise it picks up. But what totally baffles me is that physically touching the mic enclosure (which is made of aluminium and grounded) makes the noise to fully dissapear. It happens too when tapping with my toe the mains ground pin directly from the wall.

So it seems that I have to ground myself to solve the problem, which seems pretty strange by itself.

As a side note, I had this same behaviour some time ago with a bass guitar, which made awful noises when I was not touching the strings, and it was solved by connecting a cable from the strings to any part of my body's skin.

Pin 1 of the XLR connector is tied to the enclosure ground, but I've tried it both ways.

Am I "EMI ill"? What can be the cause of it?

Best regards

 

[billshurv]

are you wearing shoes? and what is the flooring?

 

[regiregi22]

A pair of flip-flops, and floor is made of wood

 

[billshurv]

can you try barefoot just to see if its static building up. When you touch the mic you earth yourself.

 

[DF96]

RF parasitic oscillation? Adding a large lossy capacitance (you!) damps the resonance and stops oscillation. Parasitics often show up as strange hum problems.

 

[regiregi22]

After some troubleshooting and ripping off the capsule's assembly, I've realized there was indeed a grounding problem in both capsules I've tried. I made a bad cold solder joint and the connection that I point with a red arrow wasn't making good contact. It has taken me several days and opening a thread here to realize my incompetence.

Now it is working perfectly, no noise near or far away from me. Problem solved.

Sorry guys from bothering you. At least I am sure I'm not an EMI-radiating alien