DOEPFER System A-100 Synthesizer Voice A-111-5
9
3. In- / Outputs
1 VCO Frequency Control Input (1V/Octave)
This input is used to control VCO frequency from the socket
at the front panel. It works in addition to the control voltage
that is applied to the CV line of the A-100 bus – provided
that the corresponding jumper JP2 is set (details in the
appendix) – and the internal frequency settings and
modulations (controls 1, 2, 3a and 3b). Both CV inputs can
be used simultaneously (e.g. bus CV controlled by the Midi
interface A-190-2, front panel CV connected to the output of
a A-155 sequencer or vice versa). For precise 1V/octave
characteristic a buffered CV source is recommended (e.g.
A-185-1, A-185-2, A-190-2).
Both CV inputs can be used to "play" the VCO by means of
a control voltage that uses the 1V/octave standard or to
modulate the VCO e.g. by an LFO or another VCO. To
adjust the level of an external frequency modulation an
attenuator (e.g. A-183-1) or amplifier (Ae.g. -183-3) can be
used.
2 VCO Pulsewidth Control Input
This is an external input that can be used to control the
pulsewidth of the rectangle by an external control voltage. It
works in addition to the manual control of the pulsewidth
(control 5) and the internal PWM source (controls 6a and
6b). The external PW voltage is not processed by the
attenuator 6b. A voltage difference of about 5V is required to
cover the complete pulsewidth range (e.g. 0…+5V or –
2.5…+2.5V according to the setting of the manual
pulsewidth control 5). If a smaller range is required an
external attenuator module has to be used (e.g. A-183-1).
3 VCF Frequency Control Input (1V/Octave)
This input is used to control VCF frequency from the socket
at the front panel. It works in addition to the internal
frequency settings and modulations (controls 7, 8, 9a and
9b). The socket can be normalled to the bus CV line
provided that the corresponding socket JP12 is installed
(details in the appendix). For precise 1V/octave
characteristic a buffered CV source is recommended (e.g.
A-185-1, A-185-2, A-190-2). The external VCF control
voltage is not processed by the attenuator 9b. To reduce the
sensitivity of this CV input an external attenuator module
has to be used (e.g. A-183-1).
4 VCA Amplification Control Input
This input is used to control VCA amplification (or loudness)
from the socket at the front panel. It works in addition to the
internal amplification settings and modulations (controls 12,
13a and 13b). The external VCA control voltage is not
processed by the attenuator 13b. A voltage of about +5V is
required to obtain the maximum amplification (provided that
