[sdiy] slightly OT - earth hum

[Dave Kendall]

Hi.

I may have to modify a mixer or keyboard, so it's not that OT... I have 
a nasty hum/noise problem, and maybe someone here has hit this problem 
before....
A Tapco 6306 mixer is connected to a Yamaha O3/D. The tapco hums loudly 
(60Hz with harmonics) with no audio connections made. It stops humming 
when balanced audio jacks from a Kurzweil K2661 are connected to it.

  The K2661 has a 3-pin mains input, the Tapco is a wallwart (9V AC)
As soon as a Nord electro (2-pin mains) is connected to the Tapco, 
There is a horrible digital noise from the Nord, modulating in a 
pattern at a few kHz or so I guess.
However when Midi out of the K2661 is connected to the nord's MIDI in, 
all the problems go away.

Would it be worth Modding both the tapco and the nord to accept 3-pin 
mains somehow?

Anyone done this sort of thing before? Any advice would be most welcome.

Apologies if this is too off-topic....

cheers,
Dave