[LAU] Am I experiencing ground hum or is it something else?

[Andrew C]

Hey all,

I'm just wondering, is the start of this short recording a ground hum
loop? It appears to be a weird high pitched whine in there as well...

This was recorded on my yamaha psr e-403 keyboard going into my PC via
the Phones/Output on my keyboard.. I've ruled out the fact that it's
my PC/soundcard by trying it with an amp in a different room away from
my  PC, but I still hear that annoying whine.

Also plugging my headphones into the phones/output port on my keyboard
results in that annoying whine disappearing...

http://moose.linux-coders.org/what3.mp3

Could a DI box solve this problem?

Thanks,

Andrew Coughlan