Alesis multimix line 8 Transformer question

[Luis <louie.angulo@yahoo.com>]

Hi folks,
I recently bought a new alesis line 8 multimix rack mixer from the U.S.
In the back there is a voltage switch which i change before using here 
from 115 to 230v
I plugged it in here in germany but the whole chasis vibrates and it hums 
quite loud
Any ideas?
Thanx
L.