Compensating for proximity effect or bass heaviness by changing tube

For example on the Pleiades V6 head amplifier by changing from EF183 to EF89.





(Cc is 22nF)


For same conditions changing from EF183 to EF89 the anode current is reduced. Therefore the internal plate resistance is reduced and therefore the low cutoff frequency of the RL circuit formed by said output impedance and the output transformer primary inductance.


By a simple electron tube change without modifying the circuit one could come closer to the microphone with natural sound preserved.


See also open grid operation of these electron tubes on god yes euroelectron posts.