Understanding Tube Amp - Biasing a Triode - a nice video

[kagliostro]

http://vimeo.com/33244955

K

[SILVERGUN]

Great video(s) there....thanks for posting!

[PRR]

I would object that "cathode saturation" is a non-issue in our work.

Oxide cathodes saturate at currents FAR above any useful operating point.

In fact oxide does not show the clear saturation of tungsten filaments. And if you tried to get that much current happening you would quickly ruin the tube, either rip-up the oxide or burn the plate and grid.

In most audio, the only significant limit is Positive Grid. As he says, now the tube becomes hard to drive. Negative grid is easy, like a racing bicycle on good concrete. Positive grid is the same bike in deep mud.

This is important because there ARE circuits which drive grids positive. A few big audio amps go slightly positive. A few rare battery-radios were "zero bias" and swung grids positive. The BIG (>5KW) audio amps we used to use in radio transmitters generally slammed the grids very positive, driven by another very large power amplifier. You CAN get a lot more current this way. At the many-KW level, another pair of somewhat smaller tubes is cheaper than adding enough big tubes to do the job all in negative-grid mode.

Saturation does matter on a few radar pulse tubes which pass HUGE current for less than 1% of the time.

Good graphics.

[kagliostro]

Many Thanks PRR

as always your explanations are very important to understand what is back of things 

Thanks again
K

[TubeGeek]

Nice video, thanks for sharing!

[eleventeen]

Very nice, nice graphics. One of the better explanations of load line charts I've seen.