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Re: I wanna tube! Please advise

"I can see this being the case. It just seems that the first stage APM'd signal should go to the cathode and not the grid....the grid input just seems to be a modulation signal (thereby not needing to be a strong signal). This is what confuses me."

I think I understand the way you think about it. Amplifier doesn't produces power, it takes a power from a power supply and, as you point that out, modulates it with the signal. Try to think of a tube as a kitchen faucet valve. One end of it is connected to a high pressure water line (B+), another points out to the sink (ground). Now, you are putting your hand on the twisty part of the faucet (grid) and while listening to your favorite music, keep opening and closing faucet. There you got it, an amplified signal in the shape of the water stream. The same happens with electron stream. Valve is sitting between high potential (B+) and the ground and by adjusting the grid voltage more or less current goes through it. All the power, however, comes from the power supply. In multistage circuit, the last valve is the one that controls the output power of an amplifier. For it to conduct a lot of power, its grid voltage has to be swung over a very wide range. In order to achieve that range, the previous stages are used.

"Now this sheds a LOT of light on things! This is something I can wrap my mind around. Is this what is happening with so many of the SET designs where there are only two tubes in the circuit?"

I'd say yes.

Jenya


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