SSE Screen Voltage for 6550

[tunertom]

Hi Folks:

Noobie question:

I am building a SSE using a 5K OPT (Hammond 1628SEA) and a pair of Tungsol reissue 6550s. From the Tungsol original spec sheet, the max G2 screen voltage is 500V (versus 600V for the KT88) for triode and UL modes.

G2 on the SSE PCB connects to either the plate or UL taps via a 100 ohm resistor and switch. If I run the tubes conservatively at 30 watts dissipation with, say, 400V across the tube at 0.075mA (B+ about 450V), it looks to me that the 12AT7 can drive the grid negative only about 17V when the loadline hits the G2 500V limitation.

I've been reading Morgan Jones etc, but have not yet got my brain to wrap around how screens behave under triode and UL modes and whether excursions past the G2 max voltage under dynamic conditions is a no-no.

Is this something to be concerned about / should I be using a lower B+??

Maximizing output power is not a priority in my application - avoiding sparks takes top billing......!.

Many thanks!

Tom