Output Tube

[surfsup]

How does one determine the bias for the output tube without knowing the Voltage measurements? (in terms of designing an amp)...

I went through the ax84.com doc on p1-x theory and it all makes sense until the power stage, where the document tells you to do the math based on the voltage readings. Well, if I didn't build the amp yet and fire it up, how does one get voltage readings at the grid and cathode?

[martin manning]

see: http://www.freewebs.com/valvewizard1/se.html

[tubeswell]

How does one determine the bias for the output tube without knowing the Voltage measurements? (in terms of designing an amp)..

plate and mutual characteristics charts and load lines

[marcoloco961]

see: http://www.freewebs.com/valvewizard1/se.html

+1

[Phil_S]

You build it to the schematic and adjust it when you have actual readings. If you are departing from the schematic design, then you guess or estimate, set the initial bias on the basis of what you expect.

The P1 is cathode biased. If you build it as shown, that cathode resistor will work for 90%+ of the available output tubes. While you should check the result, this is not something on which to focus your pre-build energy.

[surfsup]

Okay thanks guys. The output stage seems pretty easy then. I think I'm good on that (so far for simpler amps without much going on...).

Going to start deconstructing the P1x_HO schematic now (which is the one I ordered from ax84.com)...thanks again to all that are helping.