Buying power tubes and interpreting Tube data. Gm vs Mu does anyone understand this stuff.

kipple

jpfamps said:

kipple said:

jpfamps said:

Power valves that break up earlier presumably will be those that generate less power, and thus will be driven into clipping earlier than valves with "later break up".

This would be very easy to test; you simply put the valves into an amp and measure maximum power.

You may then be able to correlate this with other valve parameters such as Gm.

@jpfamps Does a High Gm number mean high transconductance are they the same thing

Yes.

Gm is the symbol for transconductance.

Transconductance is the amount the current conducted by a valve increases with a change in the voltage on the control grid.

I can either be measured statically by simply changing the bias voltage on the control grid and measuring the change in current, or dynamically by applying an AC voltage to the control grid and measuring the AC current through the valve.

In both cases gm is then calculated by dividing the current by the voltage (I/V).

Valves will have an acceptable range for gm, and as valves wear gm reduces and hence power output goes down.

Thank you for that