At your risk. Take safety precautions. Any voltage or current can be dangerous. A suitable fuse must be in series with any battery for fire hazard protection.
It has that Yesterday - Beatles vocal quality.
Anode to grid bias is by a 20MΩ resistor. Not known yet what the optimum is. About 2MΩ decreased gain dramatically.
Signal path:
male singing voice - Fostex M80RP at 7in - Pleiades (130Ω,40mH) - Pleiades V6 schematic implemented with the CV2269 electrometer electron tube with Peerless 4722 input transformer and Pleiades 10:1 output transformer powered by a 1.4V battery - Sony TC-D5 Pro mic in - Sennheiser HD580
Electron tube CV2260 booster front end amplifier operating conditions are:
Approx 1.4V at electron tube anode
Approx 10-15 μA anode current
Low noise. Not the lowest noise. It seems if it becomes lower noise by increasing for example anode current sound quality would become bass heavy by change in anode internal resistance.
Various top quality mics had been tried such as:
Beyer M119
Revox D19
Fostex M55RP
Revox M3500 (Beyer Dynamic M201?)
Shure SM63
They all sounded so different as if coming from a different planet.
Suddenly breadboard contacts were self cleaned and preamp became much more low noise.
It is amazing what can be done with just an electron tube.
Still it is not the lowest noise preamp but it discriminates very much between open low impedance circuit and 0Ω linked XLR.
Electron tube smooth and great natural sound.
The 2DV4 Nuvistor electron tube, see previous post, at 1.4V gave lower noise but mid peaky sound. Anode current is much less at such low anode potential.
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