[Amps] re Reduction of 50hz hum via metal plate

[Vic Rosenthal]

RICK COLE wrote:
> Can some-one give me a short explanation WHY a piece of METAL should improve
> the hum...I have 50hz mains power here in Australia and never seen this here
> in any of the amps i have looked at...I have tried to reason why the metal
> REDUCES the hum but so far cannot come up with a feasable answer...to me
> anyway!!

Perhaps it stiffens the chassis, reducing the soundboard effect.  Or 
increases the mass of that part of the chassis, causing a change in its 
resonant frequency.  Since aluminium was specified, maybe the softer 
metal absorbs some of the vibration, turning it into heat rather than sound.

In other words, it's an acoustic or mechanical issue, not an electrical one.

Vic K2VCO