Instead of the internal JFET...
It should be possible to connect the electret mic element to grid through a capacitor.
It should work greatly if the grid is at space potential. Ie open grid. No grid current. No external pull up or pull down bias. At such condition the input imoedance of an electron tube is nearly infinite?
Tte Pleiades V6 circuit could be used with no resistors or input transformer. Just a coupling capacitor and say 9V-12V or a bit more voltage at the anode. (Always use a suitable fuse with any battery for safety).
It has not been tried yet but trying electron tubes at space potential had made such sensitive Pleiades V6 that just taping a Nuvistor can produce sounds. By vibrating cables etc.
An electrometer tube should be great too. See also Pleiades V1.
The idea of using electrometer electron tubes for condenser microphones comes from disk cutting lathe specialist Sean Davies.
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