The experiment below was also done with a Sonotone crystal microphone connected directly to the grid of EF183 electron tube through a 220nF coupling capacitor.
Since the Pleiades connected EF183 with a resistor from anode to grid has an approximate 100k input impedance, bass is already compensated thanks to the microphone's effective series output capacitance (making a low cut filter with the 100k impedance.
The excellent sound was high cut with a anode shunt capacitor of the order of 10 to 33 nanofarads.
The Grapian ribbon mic with 2.3mH Pleides input transformer did not need much any treble reduction as natural sound was already there.
There was some exceeds bass which could be further cut with a 10nF coupling capacitor from anode to the mixer mic input.
Since the Pleiades connected EF183 with a resistor from anode to grid has an approximate 100k input impedance, bass is already compensated thanks to the microphone's effective series output capacitance (making a low cut filter with the 100k impedance.
The excellent sound was high cut with a anode shunt capacitor of the order of 10 to 33 nanofarads.
The Grapian ribbon mic with 2.3mH Pleides input transformer did not need much any treble reduction as natural sound was already there.
There was some exceeds bass which could be further cut with a 10nF coupling capacitor from anode to the mixer mic input.
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