User manual

Amplitude and Brightness
DYNAMICS
A short gold wire indicates the wired connection from the BALANCE to the
DYNAMICS circuit (Figure 46). The DYNAMICS circuit provides simultaneous control
over the Amplitude and Frequency content of the signal coming from the BALANCE
circuit. It is in essence, a Low Pass Voltage Controlled Filter-Amplier. One way to
listen to the eect of the DYNAMICS circuit, is to set up the Drone Patch (Figure 9,
Page 10). Set the DYNAMICS Panel Control to Full CCW. Set the BALANCE Combo
Pot to 3 o’ Clock. Set OVERTONE Panel Control to EVEN and MULTIPLY Panel control
to NOON. You should hear no sound. Now, slowly sweep the DYNAMICS Panel
Control to Full Clockwise. As you do so, the sound gets both louder and brighter
while the DYNAMICS Activity Window [Lights Orange].
As you further increase the level of the DYNAMICS circuit, the sound becomes both
louder and brighter, functioning in a way that is similar to that of the Buchla 292 Low
Pass Gate: a fundamental element in the sound of West Coast Synthesis. However,
rather than using the Vactrol component that gave the Buchla 292 its characteristic
“slow” sound, the DYNAMICS circuit utilizes transistors in a topology that has more in
common with East Coast instruments and perhaps even Far East Coast instruments :)
This combination of West Coast technique and East Coast circuitry is 0-Coast
synthesis at its nest, allowing the Low Pass Gate to be used in tandem with an
extremely-important East-Coast synthesis circuit: the 4-stage Envelope we call
CONTOUR.
CONTOUR
In order to really understand the eect and
use of the DYNAMICS circuit, you must also
get to know the CONTOUR circuit, which is
Normalled to the DYNAMICS CV INput, as
indicated by the gold wire connecting the
CONTOUR Signal OUT to the DYNAMICS CV
IN Figure 47. You may recall that the
CONTOUR circuit has the Gate INput
Normalled to the MIDI A Gate OUT, so striking
any key on your MIDI controlleror running a
MIDI sequence generates a Gate that initiates
the CONTOUR circuit. If you are not using
MIDI, you can patch up Default Percussion
Sound (Figure 52). You should hear a
percussive sound and you should see the
CONTOUR function window and the DYNAM-
ICS Activity Window <lights> to indicate
activity as these Gates are generated.
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Figure 47:
CONTOUR Normalization
Figure 46:
DYNAMICS Normalizations
What is a VCA?
A VCA uses one signal to control the amplitude of
another.
Figure 48:
VCA Response to Unipolar Control Voltage
The Control Signal is an Envelope (0-8V), the Audio Signal a Triangle Wave
(+/-10Vpp). The result at the output is a Triangle Wave whose amplitude is
controlled by the envelope.
+5V
-5V
+5V
-5V
The Control Signal is now a low-frequency Sine wave (+/-10Vpp), the Audio
Signal is a Triangle Wave (+/-10Vpp). Note: the Negative portion of the Control
Signal has no eect, as the amplitude of the signal cannot go below zero.
Time
Figure 49:
VCA Response to Bipolar Control Voltage
Time