How would the electrometer tube CV2269 sound with more than 1.2V at the Anode as a microphone booster preamplifier?

 

At your risk. A suitable fuse must be connected in series with any battery for injury or fire hazard protection.

 

The Pleiades V1 microphone booster preamplifier using the CV2269 operates with 1.2V for both heater and plate. See other posts for schematic.

Rethinking about it the plate voltage may be too low and the very very low plate current could be a cause of some hiss.

How would the CV2269 operate with grid at space potential (nothing connected to grid except the coupling capacitor after the input transformer)?

The electron tube has an amplification factor, μ=2.

So it should operate satisfactorily with V>2V. One has to be careful while increasing the battery supply volatge as electric field penatration to the grid (which is by default negative due to the electron cloud near cathode) will increase anode current rather abruptly.

(it is funny after a search on CV2269 electrometer tube, AI gives use as batterry operated microphone boosters, and after a search CV2269 electrometer tube microphone booster gives the Pleiades V1. But the schematic given is for the Pleiades V6 which is of the EF183 operated at an low anode poential of 3.6V.)