>The URL worked today, must have been a network problem.
>
>Look at this text........
I looked and I found a few glitches. I made some minor improvements & or
notes in the lines that begin with //.
------------------
>Triodes are Good, Tetrodes are Better....
// Cathode-driven triodes (or tetrodes) have less gain than grid-driven
tetrodes.
>Unlike triode amplifiers, the PLA800 uses tetrode tubes, which have a
>control screen grid.
// The modifier "control" confuses the screen grid with the control grid.
>The screen grid not only adds to the
>amplification factor of the tube, but also controls the electron flow
>to the plate.
// the term "plate" is archaic. Tubes have a neg.-cathode and a
pos.-anode.
>When voltage regulation is used for the screen grid and
>with the plate overload circuit, as with the PLA800, plate and screen
>currents are limited to their maximum value. As a result you will not
>overdrive the PLA800 creating sideband distortion or splatter.
>Increasing the drive power beyond 50 watts, does not increase the
>power output. Because of this self-limiting feature, an ALC circuit
>is not needed. The amplified audio, as in SSB service, is clear and
>clean, void of sibilance and distortion.
// the words "sibilance and" should be deleted from this sentence. /see
below/
>xxxx
>
>What an unusual technical explanation about screen current limiting
>and distortion!!!
* Indeed Mr. Rauch, indeed. Sibilance is the high-frequency component of
speech -- which is made by directing air over the teeth with one's
tongue. Void of sibilance, speech would sound like jibberish.
[examples: soft-c, ch, sh, f, s, z] "suffering succotash" contains s9
sibilance.
>
>The schematic shows a cathode driven PA with no tuned input and no
>swamping resistance, just straight from the driver into the cathode.
>
* Hardly good engineering. I couldn't locate find the schematic. What
or where is the URL?
thanks
>A totally non-regulated control grid bias system without a control
>grid current indicator.
>
* For Class AB1, regulated grid potential is of virtually zero value
because the grid current is zero.
>He uses the center tap of the HV transformer to supply screen
>voltage, and that is a good system.
>
* Agreed
> ...
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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