of Microprocessors

VOLTAGE-CONTROL METHODS 79
drive multiple inputs by having pins at multiple column positions along the
row corresponding to the output. Multiple outputs may also be connected
together for equal mixing without the use of Y adaptors simply by inserting
pins at multiple row positions along a single column. A complex pinboard
matrix patch is, of course, much neater than the equivalent using patch
cords. Furthermore, documentation of the patch is much easier. However,
pinboard synthesizers tend to be less easily expanded due to the subpanel
wiring between the modules and the pinboard. Also, if the row or column
capacity of the pinboard should be exceeded, either another matrix will have
co be added (and provisions for patching from one matrix to the other) or the
entire matrix will have to be replaced with a larger one. Thus, pinboards are
usually only found in "standard" models of prepackaged synthesizers.
/ AUDIO SIGNALS~
VOLTAGE- 'VVV' VOLTAGE:- VOlTAGE- ...-
CONTROLLED CONTROLLED CONTROLLED 1-------IIoot
OSCILLATOR FILTER AMPLIFIER
FREQUENCV CONTROL
INPUT
CUTOfF FREQUENCY
CONTROL INPUT
GAIN CONTROL
INPUT
POWER
AMPLIFIER
AND
SPEAKER
CONTROL VOLTAGE
OUTPUT
CONTROL VOLTAGE
OUTPUT
CONTROL VOLTAGE
OUTPUT
ENVELOPE
GENERATOR
ENVELOPE
GENERATOR
Fig. 3-2. A simple voltage-controlled module patch
A Simple Patch
Regardless of the method of patching, the important point is that the
user thinks in terms of the basic parameters of sound when a patch is being
designed. Figure 3-2 shows a very simple patch for producing individual
notes under the control of an organ-type keyboard. One of the keyboard
outputs is a voltage level proportional to the key last struck. This voltage
determines the frequency of the voltage-controlled oscillator. The trigger and
gate outputs from the keyboard then enter the first envelope generator,
which produces a voltage contour in response to these timing signals. This
voltage enters the control input of the voltage-controlled amplifier) where it
impresses the contour shape onto the amplitude of the output signal from the
oscillator, thus giving it an envelope. Finally, the second envelope generator