Doepfer A-111-1 High End VCO - Manual (Page 8)

A-111 VCO 2 System A - 100 doepfer
8
Fig. 9: f
M
= f
C
Fig. 10: f
M
= 2 x f
C
If you choose non-related frequencies for the carrier
and modulator, you can produce all sorts of vocal-like
sounds, and radio interference imitations (see Fig. 11).
The results can be surprising, as just a tiny change in
frequency can produce a drastic timbral alteration or
effect (compare Fig. 10 with Fig. 12).
Fig. 11: f
M
= 3.3 x f
C
Fig. 12: f
M
= 2.05 x f
C
The other important influence on the end result is the
intensity of the modulation - in other words, how high
the Linear FM control 7 is set.
3.3 Synchronisation
What synchronisation means in this context is that the
waveform of one VCO (‘slave’) is locked to the wa-
veform of another (‘master’), by connecting the audio
out of the master VCO to the sync input of the slave.
In the A-111 two types of synchronisation are avai-
lable: "Hard Sync" and "Soft Sync". There are accor-
dingly two Sync input sockets ($ and %).
Hard sync
Consider the following example (see Fig. 13 on page
9), in which the slave VCO is a triangle wave, and the
master VCO is a rectangle wave. The waveform of the
triangle wave changes direction every time the rec-
tangle wave hits a rising or falling edge.
If the master VCO’s frequency f
M
is bigger than the
slave VCO's f
S
, then the slave’s frequency is in-
creased, to match the master exactly (see Fig. 13a:
the ‘synced’ triangle wave T
R
‘s cycle is exactly equal
to the cycle of the master VCO T
M
).