Description - model 218e Touch Activated Voltage Source
The 218e is capacitive keyboard modeled after the original 218 built in 1973,
but adding an arpeggiator, fourth preset voltage source, and MIDI capabilities.
First, the keyboard surface and its outputs:
Tactile keyboard
Surface
The surface consists of 29 individual keys comprising 2-1/3 octaves. Each
touch of the keyboard generates a pulse, a pressure CV, and a main pitch CV.
These outputs are placed in the upper left of the 218, expecting to be plugged
directly into the nearby the pulse, pressure, and pitch CV inputs of a 208.
The
pulse
output is red banana on the upper left. A
red LED will indicate every pulse output. The
pressure CV
output correlates to the detected
amount of finger contact on the keys. The blue LEDs
next to the pressure output will get brighter as the
voltage gets higher.
The “
main
” output corresponds to the pitch of the key.
At the Buchla standard of 1.2v/per octave, that means that the pitch C will be
0v,1.2v, 2.4v, 4.8v or 6.0v depending on the octave being played. (Notice how
conveniently that relates the MIDI “C” notes 0, 12, 24, 48 and 60.) Every
½
step higher will be .1v higher.
To the right of these outputs is
Portamento
control.
Adding portamento will make the pitches slide from one to
the next like a violinist sliding a finger to the next pitch. It is
an endearing musical affect. To control the speed of the
slide, turn the knob higher. At 0, it does not slide; At 10 it
may take several seconds to reach the next pitch. The input banana is
another way to control this parameter with a CV. The CV input will add to the
portamento time set by the knob.
To the right of portamento is the
Arpeggiator
.
The 218 will arpeggiate based on the keys
that are sustained with the fingers or sustain
pedal. The rate can be controlled by the knob
or the CV input. The switch determines
whether the arpeggiation is active or whether it plays an ascending or a
random pattern.
(Note: pulse outputs during arpeggiation are 10v pulses with sustain, and
therefore the voltage drops to 5v and does not drop down to 0v.)
