What I meant above is the design of the driver section of the circuit. Your amp is using a 6L6 to drive a 300b, which is a good choice. I was referring to many 300b amps that are pushing tubes like a 6SN7 to the max and barely driving a 300b. The first rule of amp design is your driver section should never strain or clip before your output section does
It seems perfectly rational that the driver stage of a tube amplifier is of paramount importance. If the output tube isn’t adequately driven then how could optimal sonic performance be achieved? The builder of my 300b SET chose the 6EM7 as a very suitable driver for the 300b. His reasoning was the same as you mentioned.
I am not an electrical engineer but I wonder how much is it the particular driver tube versus the implementation of said tube. Ralph has written in the past that the 6SN7 is a sufficient driver tube “dependent “ on its implementation in a given circuit. I have been told that the 6EM7 provides much more current, power and drive capability compared with the 6SN7.
I will say that I’ve heard an excellent sounding PSET 845 amplifier that utilized the 6SN7. I could certainly be wrong, but isn’t the 845 a more difficult tube to drive than the 300b? Anyway, no question that driver stage rivals power supply and output transformers in getting it right for tube amplifiers. So it appears that there are alternative executions that can get one there successfully.
I very much appreciate the comments this thread has generated. The education never stops.