Best practice when rolling tubes?

[rbc3]

I read in the manual that for the soft start circuit to work, the amp has to be powered off for more than 20 minutes.  So I figure that's a good time to wait before swapping out new tubes when tube rolling.  Are there any other best practices when tube rolling?  Will the hum balance need adjusting when new tubes are rolled in?  I'm going to drop in some 50's era GE 3 mica mil spec 5670 tubes tomorrow and try a NOS pair of KR VV300B tubes after that.

-Robert

 

[Grainger49]

The soft start is there to keep the voltage on the 2A3 grid from being too high at startup.  This only is a problem with the direct coupled 2A3 version of the Paramount.  And it is only a problem to some specific new production tubes, not NOS.

There is a way to "suicide" the soft start circuit but I wouldn't post it unless Dan approved. 

As for the hum balance, it applies to any swap of the output tube.  Swapping the driver doesn't necessitate any adjustment of the hum balance pots.