[sdiy] slightly OT - earth hum

[Ben Lincoln]

Dave, you've probably already looked into this, but are all of your 
devices on the same mains circuit? Nearly all of the ground noise issues 
I've run across over the years were the result of connecting things that 
were powered by different circuits.

It sounds like that's not what's going on with the mixer itself, if it 
hums with literally nothing else connected to it, but maybe it's what's 
happening with the Nord + mixer combination? Is the mixer physically 
grounded/earthed by some other means, e.g. it has a metal case and is 
sitting on a metal cabinet that's sitting on a concrete floor, or 
something like that?

On 2011-03-24 07:02, Dave Kendall wrote:
> 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
>
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