Phantom powered electron tube microphone booster amplifier?

At your risk. Take all safety precautions before using any voltage.


Referring to Pleiades V6 schematic...


Today the V6 schematic was redrawn on the beach just before sunset. The gentle sea waves kept erasing the bottom battery heater and anode supply part..


So it was decided to just take a centre tap from output transformer secondary (ie phantom voltage supply) and connecting it as Vb to output transformer primary which then feeds the anode.


And then also connecting a series resistor to the phantom voltage supply and feed a direct heater filament electron tube cathode with 1.5V or less. Filament heaters of hearing aid tubes require just 10mA. And of some 7 pin subminiature tubes just 50mA. See previous posts.


The heater dropping resistor could if needed be used for bias as on the Neumann U47 schematic.


The cathode can be connected to ground or through such part of dropping resistor.


Pleiades bias can be used from anode to grid but it should not be really needed as 48V is plenty to create even large anode current which should not be needed anyway.


So to summarize:


An EF14 electron tube underheated as VF14 is on Neumann U47 could be heater powered by a say 3.7V battery (use always a fuse in series with a battery for safety) and then the anode powered by phantom power.


Of if phantom power current capability allows getting both heater and anode power from phantom power.



Grid at space potential can be tried too (see older posts). It should be fun.


(Would this arrangement be useful for moving coil, ribbon or printed coil ribbon mics stepped up by input transformer, electret or non electret condenser capsules, crystal mics, Olson grid electronic microphone etc?)