Ground loops and hum

Hi...

I just finnished my novo kit, and besides some problem cutting the pot (solved right now), everything went as the manual says... but i have a big problem with a ground loop, but only with low impedance headphones.

I have at home some AKG141 Studio and a K240DF both rated at 600ohm, and the Novo works like a charm with them (a little exhausted becouse those high ohms, but perfect for my ears).

The problem appears with the other low impedance headphones: I have a k181DJ rated at 42Ohms and a ATH-W1000 rated about 40ohm if i don't remember wrong. With those low impedance heads, the hum is complety insane, on both channels. If i touch the Jack connector with my hands, breaking the ground loop, the hum tends to dissapear, although some hum is still audible.

I have checked twice the components, and everything seems to be ok, (both two ground wirings from the enclosure to the RCA's and the POT too)

Do you have any idea of what is happening here?
Tomorrow i will add the capacitors you say at the manual (10pf, 50v or more) to see if something changes.

Btw, i'm using and IPOD (batteries) and a good minijack-rca cable. I tested it with two CD players (RCA-RCA) with the same behavior at low impedances.

Thank you.
Knob2001.

check that the serated washer is "breaking" through the anodise to make contact between circuit ground and case (that was the fault on my phono preamp)

Hi!

That was exactly my problem
For a reason i can't explain, the washer i used was a normal one, not the serated one you told me about and the anodise was repelling the ground connection. It's funny how the smallest thing can ruin everything, isn't? Anyway, the hum has dissapear, and it sounds the way is supposed to sound. No matter the impedance of the heads.

I have learned a very usefull tip for the future, so thank you twice.

Regards
knob2001