At your risk. Any voltage or current can be dangerous . Take all safety precautions. Any battery should be used in series with a suitable fuse for fire hazard protection or self protection etc.
This circuit drawn today on the sand under the very early morning sun is
similar to a long tailed pair with input and output transformer with the following differences:
A say 8MΩ pull up Pleiades bias resistor from anode of top electron tube to its control grid. Same for the bottom electron tube. This should allow operation of amplifier at very low anode potential. See previous posts eg Pleiades V6 schematic. It is also a path for not allowing the control grid becoming too negative by the grid rectification effect.
Cathodes or one side of filaments connected to ground.
How would this kind of amplifier sound with a direct low power consumption double triode such as 3A5?
https://frank.pocnet.net/sheets/127/3/3A5.pdf
A small battery should be adequate for the low consumption filaments. One or two small batteries of more voltage for the plate supply. Or using a centre tap to output transformer secondary for getting Phantom Power supply. Always use a fuse in series with any power source for safety.
This circuit can operate in class A (electron flowing all the time without the potential problem of DC saturation of output transformer by quiescent current which should be very small anyway. Second harmonic generation should be reduced, possibly not a good thing.
It may be a good exersice making a Pleiadws V6 single ended battery powered battery low noise preamplifier and compare.
A Pleiades (R,L) gentle slope high pass mic inline filter can be connected at the input or output if flat frequency response from input to output is not desired but flat frequency response from singer's vocal chords to listener's brain is desired [Lowe, Morgan]. The filter can be incised the preamp,box it self with various switchable ring core inductor and variable R in series for different mic impedance, mic type, singing distance etc.
It is interesting that the schematic of this amplifier becomes a symmetric square when it is drawn. This was observed better when the schematic was seen by turning the back from the sea or sun to facing the sea. Signal also should pass even if the amplifier is not powered are the 2 transformers are connected by the 8MΩ resistors.
See also:
The Pleiades bias - euroelectron
Operating features of the Audion - E. H. Armstrong
Sound Picture Recording and Reproducing Characteristics - D. P. Lowe, K. F. Morgan - Journal of the Society of Motion Picture Engineers
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