Like all push-pull amplifiers, the SRPP provides the lowest distortion when both tubes work equally in a balanced fashion, thereby requiring that the I-to-V resistor's value be carefully chosen to ensure balanced operation.
The idle current must be set in accord with the ideal operation of the circuit with the chosen output tubes and load. These restrictions disallow increasing the gain or lowering the output impedance by arbitrarily increasing the I-to-V resistor's value.
Ultimately, this circuit comprises two grounded-cathode amplifiers, not the grounded-cathode amplifier and cathode follower that is commonly assumed. Both tubes provide voltage gain into the load and both tubes only offer their rp's in parallel as the main contributors to the output impedance.
Single-ended vs. push-pull
Which view is correct? Surely, this circuit is not all that complex. Couldn't an oscilloscope be attached to the circuit and the answer be revealed?
Yes, a scope readily reveals how the circuit works, but the oscilloscope is disdained by many audiophiles. They fear anything that smacks of the cult of measurement, holding that ear allows the only path to truth. (This viewpoint is so strongly held that some audiophiles have feared my hooking up an oscilloscope to their broken tube amplifiers, fearing that in the act of repairing the amplifier, the amplifier might become contaminated by science and conventional-engineering practice, never again sounding as pure and musical. Fortunately, the owners have never seen tubes, capacitors, or resistors being made...as they say, if you love justice and tube sound, never see how either is made.)
Before we can use an oscilloscope to test the circuit, we must add a plate resistor to the top tube, as measuring the voltage drop across this added resistor reveals the amount of current flowing through the top tube. This resistor does not compromise the circuit's function.