The volume knob increases the volume. Who'd have thought...?

[Sambrook]

I have a passive bass, one single coil pickup, volume and tone.

It has the single coil hum, certainly, but an annoying buzz as well. Thinking it's an earthing problem, I've checked the groundings, but here's the rub - between 8 and 10 (max) it's as quiet as I can get it; turn it below 8, and the buzz increases very noticeably.

Could it be a dodgy volume pot? Any input gratefully received, as always...

[alyctes]

Ignorantly, I'd suggest that's a duff circuit component, in much the way that two-pickup basses need some balancing circuit or other (told you) to keep the output volume more or less similar as you change the balance between the pups.

[Jerry C]

When you reduce the volume, a part of the volume pot's resistance (from top to the wiper) gets added in series with the pickups, effectively increasing the instrument's output impedance. A higher output impedance does a poorer job of shorting out any noise picked up by the cable, so it makes its way to the amp. 

 

Try a different, or maybe just shorter cable. It might have better shielding, picking up less noise. The better solution is, I'm afraid, an active bass - or activating yours. Active electronics have low ouput impedance and are not significantly affected by long and/or not so great cables. 

Edited December 12 by Jerry C