#505 Rakit Baby8 Sequencer
Building the Rakit Baby8, an 8 step sequencer with CV and Gate outputs and a clock input.
Here’s a quick demo..
The Rakit Baby8 sequencer kit is a simple 8 step sequencer with CV and Gate outputs and a clock input.
Each step has an associated CV potentiometer, LED and switch. The CV potentiometers can be adjusted to emit anywhere between 0-5 Volts from the CV out jack when the step is active.
The Baby8 belongs to a rich tradition of CD4017-based sequencers. The design goes back to the 70’s and most people quote a column called “Captain’s Analog” that introduced a simple 10-step design called the Baby10 (I haven’t been abled to discover where this column was published or the author’s name beyond it being be a guy called Mark).
|Component||Qty||Checked & Installed|
|Stand-offs and nuts||4||√|
|10u Electrolytic Capacitor||2||√|
|4u7 Electrolytic Capacitor||1||√|
|100n Ceramic Capacitor||3||√|
|SPDT Switch - right-angle connector||1||√|
|SPDT Switch||8||√ (missing 1 in kit)|
|78L05 5V Regulator||1||√|
Rakit have a very clear assembly guide online. Recommended build sequence:
- resistors (except for 4093 bodge)
- battery clip
- mono jacks
- power switch
- 4093 bodge resistor
After an hour or two - the finished kit…
How It Works
The core of the sequencer is the CD4017 decade counter. This is nothing earth-shattering however - it simply uses the CD4017 as a designed as a decade counter. Each output has a potentiometer to set a specific output level, and diodes are used to steer the outputs to a common CV output.
The Baby8 embellishes the idea with:
- a switch on each output that will either cause the sequence to reset at that output, or skip the output (depending on a master reset/skip selector switch)
- optional external clock source
- 5v regulated power from a 9V+ external supply
A CD4093 Quad 2-Input NAND Schmitt Trigger is used for:
- a NAND oscillator to provide built-in clock source (with adjustable frequency and duty cycle)
- buffer the clock for a few different uses: driving a clock LED; triggering the Gate output
An LM324 low-power quad operational amplifieris used for
- clock duty cycle control (as a comparator)
- output buffering and amplification
Test: Sequencing the Rakit Drum Synth
Some tips published on the Rakit blog: Baby You Can Bang My Drum: linking the baby8 & drum synth
- CV Out ⇨ Pitch - the CV out for each step is set with the corresponding pot. Feeding this into the pitch input will change the pitch at each step.
- Gate ⇨ Trigger - the gate triggers the drum synth at each step.
Here’s a quick demo of the Baby8 driving the Rakit Drum Synth..