Hey everybody,
After days and days of whacking this thing about (I'm trying to install my bugle + PS into an aluminum chassis), I finally managed to reduce my incredibly annoying hum down to something "better", although still not satisfactory.
My biggest problem appeared to be that the RCA jacks weren't insulated from the chassis. I installed some neoprene washers on the inside of the chassis in place of the metal washer. That seems to have reduced my hum the most.
I think it's a ground loop because when I sampled the hum on the computer, I saw a spike around 60Hz and then at all the accompanying harmonic frequencies. Ugh.
The good thing is that the noise now seems to be down to about -50dB, but that's still too much for me.
I don't have a picture handy, although I could get one later. What would be the basic things to look for to try and reduce this further? I'd be much happier if I could get it down below -60dB or more.
A few quick notes about what I have done:
1. Replaced all power, input and output wiring with shielded cable.
2. The ground prong from the AC is connected to ground on the bugle which is connected to a screw post on the chassis to connect the turntable ground.
3. The bugle has 60dB of gain because my cartridge is a low-output Grado Reference Sonata.
4. I pulled the ground sleeve thing (that's a technical term ya know) from the RCA jacks away from the chassis a bit thinking they might have been picking up some noise from the chassis?
5. Is it possible that the RCA jacks are still picking up hum from the chassis since only the portion of the jack *inside* the case is isolated from the chassis? If so, what can I do to isolate the portion of the jack that protrudes outside the chassis?
One last note, the hum is a few dB stronger in one channel than the other.
I hope I'm making some sense.
Thanks in advance,
David
