Walt and Randy you are saying the same thing. The confusing thing is Walt's use of the absolute value of a number versus considering the polarity. Walt, forgive me, I know what you mean, but it comes across backwards when you say "the lower the voltage the higher the current", etc.
I know that you specifically referenced that it is a negative voltage, thus the statement is true IF we forget about polarity. Just a bit confusing, that's all.
Quote:
"Randy -- with all due respect -- I have been talking about cathode current. Power tubes in my experience have a "sweet spot" with regards to the cathode current and I have found that it is not the maximum current the tube can tolerate. That said -- with fixed bias you apply a negative voltage to the grid. The higher the voltage the lower the current through the tube. The lower the voltage the higher the current. OK? With cathode bias (preferred by the late Sid Smith) the voltage drop across a cathode resistor (say about 300-ohms as a possible example) creates a positive voltage with respects to the grid potential. The cool thing about cathode bias is that it "tracks" the music flow. Many arguments out there discuss the benefits of both methods. The French company Jadis has used an old G.E. trick using both methods together. A negative voltage on the grid as a starting point together with cathode bias."
Guilty of this myself at times, I gotta think that had you worded it differently, there would be no argument. I think (hope) that most of us know that if a cathode is at or below G1 voltage, the tube will essentially run away. As you stated, it's the differential between the two, and the cathode must be positive with respect to G1.
So, without the "absolute" terms the lower the voltage, the lower the current. The higher the voltage, the greater the current. -32V on a grid (referenced to the cathode), everything else remaining the same, means less current through the cathode than -10V on the grid (G1). -10V is a higher voltage,
greater than, -32V.
That's the confusing point. I think.
Stuart