Doepfer

> And while I'm on the subject of vactrols... I can't seem to get a
> mental picture of how this planned Universal Vactrol Filter is going
> to control all these knobs, and even the knobs of other machines? It
> sounds like magic to me... :-)

The Vactrol (exactly: the resistor terminals of the Vactrol) is simply
connected in parallel to the existing potentiometer. The potentiometer is
set to its maximum value. The dark resistance of the vactrol is very high
(at least some MOhm), the light resistance only a few hundred Ohm.
Consequently the manual control of the existing potentiometer is now managed
by the vactrol by changing the resistance from the maximum value of the
potentiometer (= the maximum value of the potentiometer in parallel to some
MOhm of the Vactrol) down to a few hundred Ohms (= the potentiometers
maximum value in parallel to a few hundred Ohms of the Vactrol). Only the
lowest range (a few hundred Ohms to zero Ohm) is not covered. But this is
normally only a small fraction of the whole range (e.g. less than 0.5% for a
100k potentiometer or less than 0.05% for 1M).

For the A-100 modules we will publish the pair of solder points where the
Vactrol in question has to be connected to (e.g. A/D/R of A-140 or A-143-2,
Delay/Length for A-162, Slew for A-170, Rate for A-117, Random Rate and
Level for A-118, A/D of A-143-1 and so on). For other devices (e.g. guitar
effect units) one has to look at the schematics to find out which parameter
is controlled by a variable resistor and the corresponding solder point on
the pcb.

B.t.w. We also think about a midi controlled vactrol unit (with several midi
controlled vactrols and switches) to control such parameters including
switches via control change messages from a midi sequencer.

Best wishes
Dieter Doepfer