One design goal was to keep the control voltage outputs 100% analog (no DACs);
another was to include every cool feature ever present on every sequencer ever designed<g>. Note that this is a
classic step sequencer system, not a more elaborate pattern sequencer. A pattern sequencer
is a different animal, and would make a great complement to this step sequencer
system. However, I think I'll leave the pattern
sequencer design to Synthesis Technologies.
I spent many months designing an "all in one 10 units wide do everything" step
sequencer. It had voltage control or clock selection of the sequencer stage, 16
trigger switches, and could be switched from 8x4 to 16x2 modes. It pushed the
very edge of complexity in terms of being practical to attempt to build it using
discrete logic. The panel was huge and crammed full of
controls. Then I made another survey of all the sequencers I could find
both past and present, found 2 more
features I wanted to add, and the whole thing came crashing down under its own
So I went back to the drawing board, and repackaged everything in a more modular
fashion. When I did this, the whole thing fell into place. I got all the features I wanted by
designing several complementary sequencer components, and got the complexity per
unit down to where I feel I can still build them using mostly discrete logic. It revives the
E-MU system of
separating the address generation from the voltage and gate sources, with binary address
outputs and inputs to connect the different modules (often normalled behind the panel). The pot
matrices are spaced slightly closer than standard MOTM spacing - 1 1/2" vs. 1 5/8" - but do not feel noticeably more cramped to use. The extra real estate
is necessary to add LEDs, etc.
The sequencer system's modules can be divided into 3 categories:
- Address generation (stage select) modules - these
modules accept either clock pulses or control voltages as
inputs, and provide binary addresses as outputs on several
- Control voltage, gate, and pulse generation modules -
these modules accept binary addresses as inputs, and select a
stage to connect control voltage, gate or pulse signals to one or
more outputs. Multiple modules can be chained from the same
- Sequence timing modules
This is the basic module for generating up to 16
addresses. It is nothing more than a 4 bit counter
with all the control inputs and outputs exposed. Multiple units can be
cascaded by plugging CARRY and BORROW outputs to UP CLK and DN CLK inputs. In addition, the preset
input is available on the pcb for external control
from the DAB-1018.
Inputs - UP CLK, DN CLK, HOLD, and RESET. A red
LED indicates HOLD status.
Outputs - ADDRESS 0 - 3, BORROW and CARRY
(indicates underflow and overflow). Amber LEDs indicate the
current binary count.
DAB-1018A Address Generator Interface
This 8U module was designed to provide flexible real- time live performance capabilities
the sequencer. It connects to a DAB-1016
behind the panel and takes over control of the
counter. Notice that the jacks are at the top of
this module - it is designed to be mounted in a
smaller performance enclosure close to the
Each of the 8 stages contains two rotary
switches, a pushbutton, and an amber indicator LED.
The next stage to be selected is determined by
the settings of the mode knob for the current stage.
Reversal of direction and stage skipping are supported as well as
stopping and selection by control voltage. The
pushbutton overrides other settings to force stage
selection immediately. An onboard analog to digital
converter allows stage selection by control voltage.
The CV input may be set to immediately override
everything, or to select the next stage only if
desired. A pulse/gate buss allows two outputs for
driving other modules, and can provide gates or
The second rotary switch selects a fixed control
voltage to be output from the 1018's DURATION jack.
These are used to control a 1V/Octave VC Clock
in musical terms of quarter note, eighth note,
eighth note triplet, etc.
Inputs - CV IN, SET 9-16, pushbutton SET 9-16.
Outputs - POSITION
9-16, PULSE 1, PULSE 2, DURATION CV. Amber LEDs
indicate the current stage.
Connections behind the panel - ADDR 0-3, PRESET
0-3, LOAD, RESET (from DAB-1016 Counter); STOP, UP,
DOWN (from DAB-1017 Clock Controller); CV, STOP,
RESET, SKIP, REV buss, ADDR 0-3, SET 1-8 (from
DAB-1018B Address Generator Interface
This module is a slave expander to the DAB-1018A and
provides control over the other 8 stages. It is 7U
Inputs - SET 1-8, pushbutton SET 1-8.
Outputs - POSITION 1-8. Amber LEDs indicate the
Control voltage, gate, and pulse generation modules:
DAB-1084 Control Voltage Generator
This is an 8U wide, addressable control voltage source consisting of 8 columns of 4 pots.
It has built in capability of supplying simultaneous 8x4, 16x2, or 32x1 outputs without
mode switching or external patching! This is similar to the Serge TKB ABCD output, but taken a couple steps further. The 8 'D IN' jacks allow for CV or audio signal
injection into the D row, for simple wave sequencing
or special CV effects.
Inputs - X0 - X2 (horizontal address), Y0 - Y1 (vertical address), OUTPUT INHIBIT (positive logic), OUTPUT INHIBIT (negative
logic), 1D IN - 8D IN.
Outputs - A, B, C, D OUT (8x4 outputs), AB, CD OUT (16x2 outputs), ABCD OUT (32x1 output). 8
amber LEDs for column position. 4 green LEDs for 32x1 row position. 4 green
LEDs for 16x2 row position. 1 red LED for output inhibit status.
DAB-1017 Clock Controller
This module turns a free running clock or LFO
into a controlled clock. It contains both inputs,
switches, and pushbuttons for starting and stopping
the clock outputs. The outputs appear at either the
UP CLK or DN CLK jacks depending on the direction,
which is set by inputs or a switch. Both the run and
direction states are controlled in the same manner -
for instance, if the RUN switch is in the middle
INPUT SET position, a pulse on the START jack causes
the clock to run until the STOP button is pressed or
a pulse is sent to the STOP jack. If the switch is
set to START, the clock runs unless a logic level
high is present at the STOP input, and starts again
when the high is removed. Setting the switch to STOP
works similarly - the clock is stopped unless gated
on by a logic level high at the START input.
Inputs - CLK IN, START, STOP, UP, DOWN, START,
STEP, and STOP pushbuttons.
Outputs - CLK OUT, UP CLK, DN CLK, RUN OUT
(provides a pulse when run state starts). Two
bicolor LEDs for direction and run states.
DAB-1000 Dual VC Clock
This module has two LFOs, optimized as clocks
with 1V per octave inputs. Each has a PULSE only
output, and a PWM input. When no PWM input is
present, the output is square. When the DUR output
of the DAB-1016 controls the frequency, rhythmically
accurate variations may be obtained on the fly by
switching the durations to different
Inputs: 1V/OCT A, 1V/OCT B, PWM A, PWM B.
Outputs: OUT A, OUT B. Two red LEDs indicate
So how can I use all this stuff, you ask?
Well, it's a MODULAR sequencer system! It can take up as much or as little panel space as you desire. The pieces are all designed to work together, and you can do many, many useful things with just a
couple modules. Some possible configurations: