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RE: Series-Pass tubes - Class C Audio Modulation



Original poster: "Mccauley, Daniel H by way of Terry Fritz <teslalist-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>


 >From what I've been told, cathode modulation works very poorly at least for
plasma speaker implementation.

The Captain



Many years ago I used an npn transistor as a series modulator in the cathode
of a 10W  VHF transmitter. The device was only a BFY51 but it worked! Can't
remember the details, but it used to be a fairly common approach, avoiding
expensive modulation transformers etc. I even used a carbon microphone
connected directly in the cathode circuit, I wonder if anyone has thought of
that as a method of modulating a small vttc, mind you I'd want a fairly long
lead on the microphone!!!
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, April 03, 2003 1:19 AM
Subject: Series-Pass tubes - Class C Audio Modulation


  > Original poster: "Mccauley, Daniel H by way of Terry Fritz
<teslalist-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>
  >
  >  >>> Could you recommend some tubes which would be available to use as
  > Series-Pass tubes???
  >
  > Thanks
  >
  > The Captain
  >
  >
  > A slightly better technique is series modulation where you leave the
  > oscillator in class-C but bring the supply voltage in through a
series-pass
  > tube. By modulating the grid of that tube you make the B+ go up and down
in
  > time with the audio. For maximum undistorted output, you make the
quiescent
  > supply voltage half of what your power supply gives: 25% power again. If
  > you were regulating the power supply anyway, you could modulate the
  > regulator tube.
  >
  > Steve C.
  >
  >
  >