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This McGown amp is using global feedback (4 ohm output tap is connected to driver). Probably not needed for UL operation but better for triode mode I guess? Can any PP guys here comment on what has sounded better in their opinion (UL with or without global feedback, triode with global feedback, triode with no global feedback etc). I'll probably play around a bit and see what I prefer but I would think that output stage output impedance would be really high with a pentode operated in triode without feedback? Too high?

Unless I am completely misreading the wiring on the switch?

It is a 3 pin, 2 position switch. Pin 1 has a UL tap going to it. Middle pin goes to Grid 2 (resistor in series). Pin 3 leads to the primary. Switch towards Pin 1 is UL and switch toward Pin 3 is triode mode?

Roscoe figured it out, per usual.
The toggle switch is a lever, with a pivot somewhere in the middle.
Visualize what the bottom half of the lever is doing......

Triode connected pentodes have plate resistances comparable to "true" triodes, for example, the 6L6GC has a triode connected plate resistance of 1700ohms, which is about the same as a 45...

We've probably hijacked this thread enough at this point, if you want to continue this discussion, it probably ought to have it's own thread...

Roscoe