Doepfer A-100(~ 40 MB) - Manual (Page 343)

doepfer System A - 100 VCA A-130 / A-131
3
3. Controls
The A-130 has a linear response: the amplification is
in direct linear proportion to the control voltage input
(see Fig. 1).
The A-131 has an exponential (or logarithmic) re-
sponse. That means that control voltage changes
have less effect at low levels of amplification than at
high levels, and makes the A-131 more sensitive and
suitable for subtle changes at low levels (see Fig. 1).
Fig. 1: Response curves for the A-130 and A-131
1 Gain
This controls the overall gain of the VCA. At "0", with
no control voltage present, there is no amplification at
all: no signal is present at the VCA’s output. Once the
gain control is turned up, amplification occurs, even if
there is no CV input present. The gain control shifts
the whole VCA response upwards (see Fig. 2).
Fig. 2: Effect of gain control on VCA response
H Note that if a control voltage is partially
negative (for instance an LFO modulating
the VCA) you need to set the VCA gain
above zero, since otherwise the input signal
is only amplified when the modulation CV is
positive (see Fig. 3).
Control Voltage ➨
10
5
0
5 10
lin.
exp.
Gain = 3
Control Voltage ➨
10
5
0
5 10
lin.
exp.