Doepfer A-155 Analog/Trigger Sequencer - Manual

doepfer System A - 100
Analog / Trigger Sequencer
A-155
1
1. Introduction
Module A-155 (Analog / Trigger Sequencer) is a com-
bined 8-step analog and trigger sequencer: it can
simultaneously produce sequences of analog voltages
and trigger and/or gate signals.
Module A-155 works very much like the Clock Sequen-
cer module, A-161, but includes many extra (and
expensive to implement!) functions.
The control section includes switches for Start, Stop,
Step and Reset - which can be operated by push-
button as well as digital signals. Above the top row,
eight LEDs show the progress of the sequence, with
each step’s LED lighting in turn.
The A-155 has two analog rows, each with eight
knobs, with which to set the control voltage for each
step. The upper row is particularly designed for pitch
control of a VCO, with a range switch giving the ability
to set pitches precisely.
The lower row of eight knobs has the ability to accept
an external signal for each step, in which case the
knobs act as attenuators for this voltage.
The variable voltages from the analog rows can either
be output direct, or can go through a sample-and-
hold section and a slew limiter (‘glide’). Using the
S&H and glide control inputs, it’s possible to select
‘hold’ (S&H) or portamento (glide) for whichever step
or steps you want.
Three rows of triggers and one row of gates are
available. For each step, a three-way mini-switch lets
you decide whether one or the other (or neither) of the
two triggers works. Each row has an LED which lights
whenever a trigger or gate is active at any particular
step.