1.2.
Jacks
– Apply a positive-going rectangular wave to this jack to trigger the module. A +5V
signal is best but the module will trigger at lower voltages.
– A control-voltage input for varying the loudness of the module. Positive voltages
increase the loudness; negative voltages decrease it.
– A positive-going rectangular pulse applied to this input will cut off (choke) the output of
the module.
– Plugging a signal into this jack will bypass the module’s noise source, passing
the signal through the filter.
—hopefully this one needs no explanation.
There are also five control-voltage jacks associated with some of the knobs. Applying a positive
voltage to these jacks has the same effect as turning the associated knob clockwise; applying a
negative voltage has the opposite effect.
2.
Detailed Description
Traditionally, drum and percussion sounds are thought of as having two distinct sonic
components. The first is a perceivable pitch, created by a resonant body such as the air within
the shell of a bass drum or tom, or the resonant frequency of a metal bar as found on a
xylophone. The second component lacks a distinct pitch and is produced by events such as the
initial contact between a drum stick and the drum head or the rattle of the wires on a snare
drum. In this vein, BoomTschak has two sources of sound signals: an oscillator and a filtered
noise generator. These two signals are mixed together to produce BoomTschak’s output.
2.1.
Oscillator
The oscillator, known as a voltage-controlled oscillator or VCO for short, generates a periodic
signal with a frequency of less than 10Hz up to about 1.3KHz. The initial pitch of the VCO is set
with a panel knob but can also be modulated with an envelope generator and/or controlled by
an external voltage. The VCO has a switch which selects one of two wave shapes: a nearly
sinusoidal shape producing a clear but soft tone, and a triangle wave which produces a brighter
tone.
2.1.1.
Wave Shaper
The selected oscillator signal is sent through a wave shaper which alters the tone or timbre of
the wave. The wave shaper works by folding the peaks of the wave. Turning up the knob
produces more folding, as shown in this illustration for the triangle wave:
