I know that it drops voltage. But suppose I could supply the voltage I wanted at the plate, would I even need a resistor? Every amp I've seen has some value of a resistor there. Why is that?

Hi Smokey

Without a plate resistor how would you take a signal off the tube? You need a plate resistor as voltage varies across it as the tube is operating. This varing voltage is then fed to the next stage.

Norm

:I know that it drops voltage. But suppose I could supply the voltage I wanted at the plate, would I even need a resistor? Every amp I've seen has some value of a resistor there. Why is that?
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Hey Norm. I noticed that most amps have at least 100k resistors, is that for gain purposes? I guess my whole problem is the power supply I have supplies pretty close to the plate voltages I want. If I put a 100k resistor in there, it'll drop the voltage way lower than I want to operate at. If I go less than 100K what will happen as the tube voltages varies with the signal inputted? Thanks.

Hi Smokey

It depends on current drawn. The more current drawn lower voltage. If you know current drawn and resistance multiply them giving voltage drop of a resistor. Resistance times current in amps = voltage

A tube with 100K plate resistor will probably draw little current and have a high gain. If it draws 1 ma (.001 amps) 100 volts will be dropped across the resistor.

Norm

:Hey Norm. I noticed that most amps have at least 100k resistors, is that for gain purposes? I guess my whole problem is the power supply I have supplies pretty close to the plate voltages I want. If I put a 100k resistor in there, it'll drop the voltage way lower than I want to operate at. If I go less than 100K what will happen as the tube voltages varies with the signal inputted? Thanks.