Your own risk, use all safety precautions.
The iPad 1/8in headphone-mic connector sends a small voltage through a load resistor which is inside it. Is it 1.8V?
It is a very small voltage normaly used to power a JFET.
Would it power a Nuvistor 7586 electron tube anode or an EF183 or a 2DS4 Nuvistor etc?
If the Pleiades V6 mic booster amplifier is used with Pleiades bias it may be possible.
The Pleiades or anode grid bias resistor may have to be reduced.
In it works it may be nice as the load resistor and capacitor would be inside the device.
All then needed to do is supply the electron tube with a heater voltage. It can be redused as the space charge condition is achieved at lower temperature the lower the anode voltage is. See previous posts and referenced papers on fluctuation noise in vacuum tubes.
So a 7586 or EF183 would need a 3.8 heater battery. A 2DS4 should be fine with an 1.2V C type battery for example. (A fuse should always be used in series with a battery for safety).
Above is the schematic where both heater and anode voltage is supplied by the same battery. In order to connect this to an iPad a Pleiades K117 JFET amplifier can be connected and it will be powered by the iPad in the same way.
So the first option if it works may be simpler as no output transformer is needed, no extra anode resistor or output coupling capacitor.
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