Pleiades (R,L) mic filter across the input of a booster or mic amplifier, preamplifier

It may be nice to have a simple or effective variable slope high pass filter at the input of a preamplifier.


The Pleiades (R,L) filter consists of just a resistor in series with an inductor and the total across the mic 2,3 output or mic preamp 2,3 input.


Very easy to disable by the flick of a disconnect switch in the rather rare case when a mic gives flat frequency response from producer's brain to listener's brain.


It is like a passive loudspeaker crossover network.


If the coil L is wound around a ring tape wound core there is no hum.


After playing a bit with various mics and R,L values, using variable Danbridge decade resitor, inductor boxes, see previous posts, values chosen could be for example:


Switchable inductors of 8mH, 16mH, 25mH, 40mH, 60mH, 200mH etc


A variable resitor from 0Ω to say 1000Ω.


A further advantage is that sound is cleared up before entering the sensitive preamplifier.


For example the Pleiades (R,L) variable slope high pass filter could be at the input (across the primary of the input transformer) of a Pleiades V6 battery powered electron tube booster microphone front end amplifier.