[Amps] 572B tubes replacements for 811A's

[Vic Rosenthal]

Wynand wrote:
> I read in the forum about replacing 811a's with 572B's as a direct drop in replacement. Can it really be that simple. I have a Ameritron with three 811a's in it. Can I just swop the 811a's for 572B's?

It's that simple, but (in my opinion) pointless.

The 572 will not produce any more output than the 811A unless you 
increase the plate voltage, which will have consequences for other 
amplifier components.  Some people say they 'loaf' at the same power and 
this means that they will last longer, but I strongly doubt that there 
will be a significant imporvement.  And 572B's are more expensive than 
811A's.

Vic K2VCO