Thanks, Ed! I don't have the technical background to understand this but do you know why hi mu tubes (like 6SL7, 12AX7, etc.) are typically used in SRPP?
SRPP can use hi mu, (6SL7, 12AX7, 12AT7) or lower mu (6SN7, 6CG7, etc) tube, it all depends on the gain requirements and application.
Using a high mu tube in SRPP gives the high gain, and a lower output impedance, as compared to the standard resistance coupled gain stage.
Something that I have been considering is using a high gain SRPP driving a low-mu SRPP, which in turn, would directly drive a power tube's screen grid,
and just apply appropriate bias voltage to its control grid. This might work well with horizontal deflection tubes, which can tolerate fairly high plate voltages, but have lower (150 to 250 VDC) screen grid ratings. Use 300VDC plate supply for the gain stage, and 450-500 VDC plate supply for the screen-grid driver stage.
Just another, yet-untried, crazy SWAG idea....
/ed B