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

[fons at kokkinizita.net]

On Sun, Nov 29, 2009 at 04:51:03PM +0000, Andrew C wrote:

> How can I check if the keyboard/power supply is grounded? The power supply
> itself is a three pronged one....

Then in most countries it is required by law to be
effectively grounded. Next question is if you power
socket is... It should be if it accepts the plug.

Since you also have this interference with an amp,
but not with the headphones it really seems to be
a grounding problem.

To only other way to explain it would be to assume
it's some high-frequency stuff which your headphones
would just ignore, but any active input such the amp
or soundcard could demodulate into the audio band.

If you're using a laptop, does running it on battery
make a difference ?

Anyway I'd try a DI box, it's good practice anyway with
all instruments.

Ciao,

-- 
FA

Io lo dico sempre: l'Italia è troppo stretta e lunga.