How does a variac affect the sound of an amp?

[guitarplayer]

I posted this in the wrong section yesterday but I know that a variac can increase or decrease the voltage going into the amp but what sound differences would there be for both increasing and decreasing the voltage? Also, I heard they were bad for the amp what would happen by running it at lower or higher voltage than normal?

 

[tone4days]

Re: How does a variac affect the sound of an amp?

note: this ONLY applies to tube amps ... running a variac so that it supplies a lower voltage will result in the power tubes being overdriven at a lower volume ... it chews up power tubes, but can result in a desireable power tube distortion ... EVH is said to have done this extensively back in the early days

running a variac so that it supplies a higher voltage is a really stupid idea that has no tone benefits and will destroy the amp

running a variac on a ss amp will probably ruin it and it WILL destroy a modeler

good luck
t4d

 

[guitarplayer]

Re: How does a variac affect the sound of an amp?

Well besides ruining a lot of power tubes, could anything else bad happen to your amp if you run it at lower than normal voltage? I heard a term used called cathode stripping or something but what is that?