It'd be interesting to listen to the audio output of the PC on a floating
device (headphones, battery powered amplifier, etc.) where the only ground
connection is that plugged into the PC sound card. If the hum goes away,
the audio isolation transformer suggested by others should work. If the
hum is still there, the transformer will probably not do much. In that
case, it's probably a problem with the square wave out of the inverter
getting into everything.

Good luck!

Harold


> As those following might have guessed I am building an in car mp3
> player. A computer powered by an inverter, into a graphic eq/booster. I
> finally got everything connected yesterday, however, there is a
> horrendous humming, regardless of engine running. I have tamed that a
> little by connecting the PC chassis to the inverter 0v with 4 strands of
> 18 guage (I didn't have anything heavier) but it is still fairly
> obnoxious. It is nearly eliminated when I unplug the audio from the PC.
>
> I am about out of ideas, could anyone please offer some hints and tips
> how to eliminate (or nearly) this hum?
>
> The gritty details...
>     I have the PC output plugged into my EQ using some shielded
>          stereo cable (20 or 18 guage I think)
>     The 12v and 0v line for the inverter are 10 guage.
>     The 12v comes from the battery post through a relay switched by
>          the accessory line
>     The inverter is in the trunk and grounded under a bolt in the
>          trunk.
>
>     The EQ is hooked up in front, power comes from the stock radio
>          connectors. Using the supplied cabling (looks like 18-20
>          guage)
>
> Thanks,
>
> Anthony
>
>
> --
> Anthony Toft <toftat@cowshed.8m.com>
>
> --
> http://www.piclist.com hint: To leave the PICList
> mailto:piclist-unsubscribe-request@mitvma.mit.edu
>


--
FCC Rules Online at http://www.hallikainen.com

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu