Doepfer A-191 Shepard Generator/16xMIDI-CV Interface (no longer available) - Manual (Page 5)

doepfer System A - 100 MCV 16 A-191
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Fig. 1: The sawtooth (1/2 note cycle) generated by
a MIDI controller value of 8.
Table 2: Typical values for controller #92 and the
resultant length of the LFO cycle.
H Because the A-191’s LFO is purely a soft-
ware device, the following considerations
apply, which it’s well worth remembering.
The A-191 uses an 8-bit D/A converter, whose maxi-
mum resolution is 256 steps per 0.02 V. Conse-
quently, the sawtooth and triangle waves can’t be as
smooth as, for instance, those of the A-145 LFO. The
waveforms on the A-191 LFO are digital ("stepped").
If you use it to control, eg, a VCO, the result is less of
a smooth continuous pitch sweep, and much more
akin to a glissando. How audible these steps are
depends on the MIDI-Clock tempo, and the divisor
you’ve chosen.
P If the steps are audible (and unwanted), you
can use a Slew Limiter (A-171) to smooth
out the waveforms.
Erratic or sudden changes of tempo or the divisor
will take a whole note to register, before the LFO
changes to this new frequency.
Controller value LFO cycle
0 LFO off
1 1/16
2 2/16 = 1/8
3 3/16
4 4/16 = 1/4
8 8/16 = 1/2
16 16/16 = 1 whole note
32 32/16 = 2 whole notes
64 64/16 = 4 whole notes
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