> The crystal D-104 needs a very high (> half meg) input resistance else
> it gives a weird frequency response.
It's weird anyway and the harmonic distortion produced by the crystal element
is very high. This is not necessarily a bad thing as
the distortion component can oftentimes be used to one's advantage...like DX
pileups. If one wants extension down to 100 Hz which
can be accomplished with the Pegasus and Jupiter, the typical crystal cartridge
really requires >5 Megohms of loading. It's
absurdly high. As the loading lessens (more Megohms), the equivalent noise of
the circuit can become problematic...and may be more
susceptible to R.F.
For the past ten years, I have been using a modified D-104 with a MPF-102 JFET
used as a voltage follower. The input Z to this
transistor is about 11 Megohms and I add about 1 Megohm of series resistance
with the transistor's Gate. As a VF, it's gain is
always less than unity but the output from the element is already more than
ample. However, this entire lash-up will be put on the
shelf as soon as my Ten-Tec Studio One mic arrives.
-Paul, W9AC
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