>
>hello,
>
>I want to thank Ian and Colin for your quick replies about eh DAF
>circuit. Reminds me of a circuit used by Norm (w6edd) in his two 4cx250b
>amplifier. He controlled the screen voltage with drive, although I
>believe he did use a negative bias on the control grid. Norm labeled the
>amplifier as using "class C linear operation." Opinions of the amplifiers
>performance were mixed "up and down the band."
Norm's DAF amplifier was one of the two amplifiers I measured. He
eventually converted the amplifier to conventional Class AB1.
>
>Next question... Less the requirement of a bias and "large" screen
>supply,
A conventional screen supply for the 4cx250Bs is hardly large. Since
screen current is typically around zero mA when the amplifier is heavily
loaded, the screen's shunt regulator can be fed from the HV bleeder R.
> why would one want to use this type of circuit?
? I have a theory on this. /// Those who are revulsed by psychohistory
should probably not read beyond this point. /// If an amplifier
builder constructs a conventional tetrode AB1 amplifier, efficiency is a
Snoresville 60%. . . Norm claimed that his DAF "linear" amplifier was
c. 80% efficient. Norm's DAF amp. was a hot topic. For those who
bought Norm's story, he came across as way Smarter than those who built
ordinary linear amplifiers. Getting Norm to acknowledge that his
voice-modulation distortion products were in the -20db to -23db region,
depending on grid current, took months of effort by myself and several
others. In my opinion, some guys use the DAF config. as an
attention-getter and ego-builder. According to phychologist Dr. Phyllis
Greenacre, some men use such tools to promote male-competence. . . .
"The sense of reality is characterized by a peculiarly sharp, quick
perceptiveness, extraordinarily immediate keenness and responsiveness,
especially in the area or the imposture. The sense of reality is,
however, impaired."
[Phyllis Greenacre: "The Impostor" Psychoanalytic Quarterly, 27:359 -
382 (1958)]
> Are there
>stated advantages by users or builders?
>
But of course.
Cheers, Skip.
- Rich..., 805.386.3734, www.vcnet.com/measures.
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