Pull up bias resistor is 1.9MΩ.
With a 1.2V AA rechargeable battery the anode current is aprox 5μA. The sound is easy and natural.
With a 1.5V AA Alkaline battery, Ia is 10μA. Sound is louder, there is less hiss, some more bass so the MD441 U3 can be used at 4-6in compared with 3-4in. When connecting a 0Ω male XLR at mic input there is much more decrease in noise. Sound is very nice. In about 10 minutes anode current decreases as the closed circuit voltage of the battery becomes 1.4V from 1.5V. It may goes as low as 5μA. It seems the battery is beginning to have an increased output resistance ie more voltage drop.
It may be a good idea to use type C or D batteries either rechargeable or non rechargeable. Always use a suitable fuse in series with a battery for safety.
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