At your risk. Safety precautions must be followed. Any voltage or current can be dangerous. A fuse must be included in series with any battery for fire hazard protection.
Various Pleiades experiments including listening experiments show that a very interesting vocal sound from a microphone is created by feeding an electron tube which operates at a low or very low anode potential. Very low in this context can mean from 0V to 9V to 12V.
Example is the Pleiades V1 mic booster electron tube preamplifier operating with a CV2269 electrometer electron tube and just one AAA 1.2V battery for both filament and anode.
Another example is the Pleiades V6 operating with a vast choice of electron tubes including conventional EF183 triode connected. Still one battery can be used to power both heaters and anode and depending on which tube is used it is possible to have a portable electron tube mic booster amplifier operating with just one AA 1.2V battery (Nuvistor 2DV4) or 3 AA ie 3.6V (EF183 or Nuvistor 7586), 9V (for example 12AU7, ECC82).
Here is the schematic of Pleiades V6:
https://www.flickr.com/photos/photoulia/35858046756
Most of these examples give a phenomenally low noise performance.
Possible reasons are:
Absence of mains power supply.
Use of very clean DC battery or solar cell power.
Low electron velocities therefore low secondary emission effects by collisions with residual air molecules.
Low temperature therefore low photoemission or thermoemision on other electrodes.
(Most areas are fully explained with relevant references on previous posts).
Most of these amplifiers use Pleiades or pull up bias to make the grid less negative than the value it self assumes by electrons escaping the cathode leaving cathode positive or grid negative with respect to cathode. Cathode is positive by the remaining unbalanced (positive) protons.
Most of the above circuits, for considerations of more interesting sound, or even higher signal to noise ratio, use a deliberate lower heater voltage. This is not as unusual as it may look at first glance if one considers the underheated VF14 electron tube on the Neumann U47 microphone.
But back to subject. It should be possible to power the anode directly from a modern device. See also older posts.
In summary it is done:
By feeding cathode heater or filament to a suitable battery in series with a protective fuse.
Connecting mic to input transformer.
Capacitor couple the input transformer secondary winding to grid.
Pleiades biasing grid with a high megohm resistor from anode to grid.
Connecting anode directly to mic input of a modern device at electret mic in.
The phantom voltage of 1-2.5 volts should be plenty. The anode load resistor where amplified signal,voltage develops is the device internal resistor.
So it is.
Now for a truly portable balanced input balanced output mic booster amp it would be nice if power consumption is so low that a small battery feeding the electron tube could last for days or at least plenty of hours.
Such consideration make the use of direct filament battery electron tubes very attractive.
For example an DF97 electron tube has filament current consumption of just 25mA. Not sure yet how well can this electron tube operate at 9V anode or whether it would need more than 24V.
An electrometer triode has even less filament current at just 13mA. It can operate even at 1.2V anode electric field potential.
So it may be worth improving the Pleiades V1 schematic by features found on the Pleiadss V6.
For example replacing anode resistor with output transformer primary so that more anode voltage arrives at anode.
Perhaps using an AA battery instead of AAA.
Or optionally adding another AA battery just for the anode circuit.
If such battery holder is used with a Lithium 3.6V battery, this would create the option of a different sound with higher anode current.
A fuse should be used with any battery for fire hazard safety.
References can be found on so many posts. One of the most important will be included here which covers from the genious of the inventor of FM most on the art of controlled electron flow by a music signal ie the art of electronics of electronic engineering or engineering electronics.
Operating Features of the Audion - E. H. Armstrong
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