Doepfer A-119 External Input/Envelope Follower - Manual (Page 6)

A-119
Ext. Input / Envelope Follower
System A - 100 doepfer
6
Ring modulator squelch patch
A ring modulator works particularly well with external
audio signals such as voices, strings, or saxophone.
In the patch in Fig. 3 a typical external audio signal is
ring modulated with a sine wave.
Fig. 3: Ring modulator squelch patch
In this patch, the A-119 has two functions. One is to
bring the level of the signal output at § and/or $ up to
the operating level of the A-100 (c. 5 V). The other is
to generate an envelope which can then control the
ring modulator’s output via a VCA.
This is necessary because the ring modulator doesn’t
shut down completely when there’s a 0 V input. It
goes to about -50 or -60 dB, and so traces of the VCO
or external signal can still be heard.
The combination of the A-119 and VCA causes the
ring modulator to shut down completely (‘squelch’) if
there is no input present.
The A-170 slew limiter smooths out the gate signal
generated by the A-119 a little, to avoid clicks in the
VCA.
P Instead of gate signals, you can use the
envelope generated by the A-119 to control
the VCA, and thus maintain the loudness
pattern of the original sound.
VCO
X IN
A-114
Y IN
X • Y OUT
RING MOD.
VCA
ext.
Audio Asym.
In
Over-
Load
Gate
Out Threshold
Gain
A-119
Ext. In.
Symm . In
Envelope
Out
Audio
Out
Gain = 0
A-170