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Four-Step Octaved Sequencer

As featured in the blog post "Prototype Post-Mortem: Four-Step Octaved Sequencer", these are the prototype PCB designs for a (yet to be totally finished) fun little noise toy.

Four-Step Octaved Sequencer PCB assembled

The PCB and its electronics are possibly available as a DIY electronics kit. This repo serves as the assembly guide for the kit, as well as the EAGLE project so you can fabricate your own from scratch, should you want to!

Demo video:

Assembly guide


Four Step Octaved Sequencer

Annotated BOM

Part Value Device Marking Purpose
C1 10uF Polarized, electrolytic capacitor Tempo timer
C2 .1uF Ceramic capacitor 104 556 IC bypass
C3 10nF Ceramic capacitor 103 Pitch timer
C4 .1uF Ceramic capacitor 104 4017 IC bypass
C5 .1uF Ceramic capacitor 104 4040 IC bypass
C6 220uF Polarized, electrolytic capacitor Amplifier
D1 Diode Step 1 output
D2 LED Step 1 indicator
D3 Diode Step 2 output
D4 LED Step 2 indicator
D5 Diode Step 3 output
D6 LED Step 3 indicator
D7 Diode Step 4 output
D8 LED Step 4 indicator
IC1 556 556 Dual 555 timer Timers for tempo (on left) and pitch (on right)
IC2 4017 4017 counter/divider Decade counter for steps
IC3 4040 CD4040 or MC14040, 12-stage binary/ripple counter Divides pitch frequency into octaves
IC4 386 LM386, low voltage audio power amplifier Amplifier
J1 ON/OFF Header connection For external switch (not included)
J2 - 9V + Header connection 9v battery snap
J3 - SPK + Header connection To 8ohm speaker
R1 680 Resistor Blue Grey Brown Max tempo
R2 220 Resistor Red Red Brown Tempo timer
R3 5.6k Resistor Green Blue Red Pitch timer
R4 10k Resistor Brown Black Orange Counter pulldown
R5 1K Resistor Brown Black Red For step 1 LED
R6 1K Resistor Brown Black Red For step 2 LED
R7 1K Resistor Brown Black Red For step 3 LED
R8 1K Resistor Brown Black Red For step 4 LED
R9 10k Resistor Brown Black Orange Mixer for octave 1
R10 10k Resistor Brown Black Orange Mixer for octave 2
R11 10k Resistor Brown Black Orange Mixer for octave 3
R12 10k Resistor Brown Black Orange Mixer for octave 4
SW1 4 position SPST DIP Switch Octave mutes
VR1 50K Variable resistor 503 Tempo
VR2 50K Variable resistor 503 Step 1 pitch
VR3 50K Variable resistor 503 Step 2 pitch
VR4 50K Variable resistor 503 Step 3 pitch
VR5 50K Variable resistor 503 Step 4 pitch
VR6 1K Variable resistor 102 Volume


  • Be sure to match polarity on electrolytic caps, diodes, and LEDs! The longer leg of the LED is positive
  • The four ICs don't solder directly to the PCB. Instead, solder the included sockets, then insert ICs.
  • IC3 may be marked as either CD4040 or MC14040. The two models are pin-for-pin compatible.
  • The J1 (on/off) header is included for convenience if you have a switch you'd like to use. If not, short the two pads together.


All done? Try these ideas:

  • Swap out for a bigger speaker to really hear the bass
  • Increase gain on the 386 with a 10uF cap between pins 1 and 8
  • Try bigger pots for the step tuners
  • Increase R1 for reaaalllly looongggg steeeppsssssssss
  • Swap R9-12 with pots to get individual volume controls for each octave as they mix together
  • The 4040 has 12 "octave" outputs but we're only using four...

Known issues

This PCB was last updated April 2018. In addition to the issues from the post-mortem:

  • Some footprints are slightly mis-sized and require bending leads
  • Volume control is linear instead of logarithmic, so range sweep isn't great
  • Battery and speaker wires need relief holes to prevent breakage over time

Version log

  • 1.1.2: Adds IC, header, and polarity labels; reorders octaves
  • 1.1.1: Adds mounting screw holes and a header for on/off switch (not included)
  • 1.1: Initial version featured in the blog post


Designed by Oskitone. Please support future synth projects by purchasing from Oskitone.

Creative Commons Attribution/Share-Alike, all text above must be included in any redistribution. See license.txt for additional details.