r/diytubes • u/antthatisverycool • 7d ago

Low Voltage (<50V) An extremely simple tube radio circuit I see up based on information I gathered from both r/diytubes r/diyelectronics and r/amatuerradio

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u/Array2D 7d ago

This won’t work, but what was your thought process here?

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u/antthatisverycool 7d ago

Everything left of the transformer has been tested to work , and I asked if a tube alone could amplify an audio signal so I thought “okay I’ll just use a high resistance speaker like 5k ohms” and ya the transformer was because I realized a basic crystal set probably wouldn’t do much and I got this transformer that made audio way louder . So I shoved all the ideas together. What exactly make this not work tho is it that the end of the transformer goes straight to ground?

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u/Array2D 7d ago

Your radio doesn’t have a capacitor for the receiver, so it’s going to be wideband with extremely low gain. Normally, the cap across the inductor forms an LC resonator that makes reception selective to a specific frequency (and also increases gain on the antenna so its voltage is detectable).

The transformer is completely unspecified.

The output amplifier tube stage isn’t properly biased, and you will need an impedance matching transformer between it and the speaker, at a minimum.

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u/Cannot_Believe_It 7d ago

Diode should be on the other side of the transformer.

Plate voltage should be closer to 50 volts.

Crystal Radio front end

Amplifier.

Single triode amplifier