The fix is to replace the pot with a resistor or two and then isolate
the pot from the collector current with a cap. That really does
defeat the design, however. The idea was to set up the transistor
gain how you want through the collector (with the pot) rather than
simply throttling the output. I love the Rangemaster! And the
Steiner VCF!!!
If you want to experiment, I do have quite a pile of germanium
transistors. Shipped anywhere, no charge.
Chub - the man who moved junk across the US.
the pot from the collector current with a cap. That really does
defeat the design, however. The idea was to set up the transistor
gain how you want through the collector (with the pot) rather than
simply throttling the output. I love the Rangemaster! And the
Steiner VCF!!!
If you want to experiment, I do have quite a pile of germanium
transistors. Shipped anywhere, no charge.
Chub - the man who moved junk across the US.
--- In cgs_synth@yahoogroups.com, "Ken Johnston" <betweenpie@...> wrote:
>
> Isn't the Synthacon res pot is like the boost control on the Dallas
> Rangemaster treble boosters for guitar? From the GEOFEX site, regarding
> this:
>
> "Another quirk of the original is that there is a DC voltage across the
> volume control, which also serves as the collector load resistor. This
> means that it will inevitably scratch and crackle whenever the control
> is moved even if you use high-collar conductive plastic pots. This was
> OK in the time of the original unit, as the designer assumed that a
> player would set up this thing and leave it, not twiddling the control
> during a number. There are ways to "correct" this, but they complicate
> the design unduly, so I have chosen to leave them out, going with the
> original circuit. It will crackle when you twist the "boost set"
> control."
>
> Alas, the fix is not explained, although I bet one could find it
> digging through the myriad Rangemaster clone schemos on the web...
> >
>