On 19 Jul 2010 at 8:58, Ben wrote:
  The main problem is the power supply, I got all crappy
open core
 inductors, that hum like mad. This will require a rebuild, but I
 don't have $$$ for that. Now I know why consumer products vs
 commercial products have a 10x difference in price. 
A short-term solution might be to fabricate an external shield over
the troublesome components out of sheet steel.
Another approach would be to physically separate the power supply
 from the amplifier.  That used to be a very common
approach. 
--Chuck