Hirokuni Michimori a legend in tube amps design introduced this Cathode Follower & constant current source circuit, using the 811A power tube.
The design features the following :
Output power vs. Input power is extremely high efficient (> 40%) in A2 class operation
Compliance to higher grid current of power tube (e.g.19.5~ 40.0mA 100TH)
Wide window of bias voltage setting of power tube (-20 V to + 40V)
Higher gm tube(5998A) makes CF output impedance lower (1/gm=64ohm for 5998A)
Lower impedance and 100 % negative feedback of CF circuit lead to be strong in stability and various transient response (e.g. signal & bias voltages are not influenced when power tube grid draws higher current,)
Applicable and versatile to almost all transmitting tubes inclusive negative bias ones
