[AMPS] G2DAF Circuit

[Colin Lamb]

"Does the fact you measured one bad sweep tube amp suddenly mean the DAF is
considered good engineering? (I don't think so.)"

I simply stated that some grounded grid amps, which happen to use sweep
tubes, have poor imd performance, yet that does not mean that all sweep tube
amps are unacceptable.  Rich measured one bastardized "DAF" amp for imd and
feels qualified to condemn all of them.

I do not object to a conclusion based upon either empirical knowledge or
logic - even if I might disagree with it.  I do object to a conclusion based
upon faulty logic and/or no empirical testing - even if I agree with the
conclusion.

Two tone testing of amplifiers will not show a possible defect in the "DAF "
circuit.  In particular, the screen voltage will be held high.  Norm's
bastardized "DAF" hung a large electrolytic cap. on the screen, which would
destroy it as a linear amp - yet it could have passed a 2 tone test.  But,
the fact that a "DAF" circuit passes 2 tone testing does not mean it will
fail.  Other tests can be used to determine the qualities of the "DAF"
circuit.  I understand tests have been done and posted to a website, yet no
one seems interested in looking at empirical results.  The attitude of a few
is "it cannot work, therefore any results which tend to indicate that it
does are flawed".

At least a few "modified" DAF circuits are in daily use in Sweden.  Tests
have been made and posted, and other hams who seem competent, have listened
and not heard objectionable splatter.  That may not prove that the "DAF"
circuit is the best circuit to use, but it may cause one interested in
scientific investigation to at least come up with a test acceptable to them
to further investigate the amplifiers that are in daily operation.

To dismiss an idea for the wrong reason, or because of a lack of adequate
testing or understanding, is perhaps as objectionable as listening to a lot
of splatter.  In fact, it is much worse.  I have a neighbor who runs a
4-1000 grounded grid, driven by a SB-200.  He overdrives everything and has
horrendous buckshot.  But, even though I operate in the same dx window as
he, it does not bother me that much.

For me, splatter is less objectionable than a closed mind!

Colin  K7FM



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