Eurorack Synth Modules

Overview

• Land Boards Eurorack Modules
  • ER-ADSR-555-01 - Eurorack ADSR Module
  • ER-MIDI-CV4-02 - Eurorack 4X CV Module
  • ER-MIDI-THRU - Eurorack MIDI Thru
  • ER-MULTS-01 - Nicklas Rönnberg Passive Multiple
  • ER-MIXER5-01 - Eurorack 5 Channel Mixer
  • ER-PROTO-01 - 6HP Prototyping (6 pots, 4 jacks)
    • MOZZI on Arduino NANO on ER-PROTO-01
    • ER-CVPOTS4 - 4 CV pot controlled outputs on ER-PROTO-01
    • Noise Generator on ER-PROTO-01
    • Slew Rate Controller on ER-PROTO-01
  • ER-PROTO-02 - 6HP Prototyping (6 pots, 6 jacks)
    • ER-BEZIER-CV - HAGIWO Bezier Random CV Generator
    • ER-CV-AMP3 - Control Voltages Amplifier
    • ER-GATE-SEQ-01 - GATE Sequencer
    • ER-LEDS - Control a NeoPixel strip
    • ER-MOZZI-DB - Arduino NANO MOZZI: VCOs, Bezier CV Generator
    • ER-SCOPE-01 - Scope
    • CV SHIFT on ER-PROTO-02
    • ER-STIX - Mutable Instruments Branches
    • ER-USB-MIDI - USB MIDI to Serial MIDI on TRS
  • ER-VCA2-01 - 2 Channel Voltage Controlled Amplifier
  • ER-VCF-02 - Voltage Controlled Filter
  • ER-VCO-03 - Eurorack RP2040 VCO
  • Eurorack DIY Panel

ER-ADSR-555-01 - Eurorack ADSR Envelope Generator Module

ER-ADSR-555-01

• Attack-Delay-Sustain-Release Eurorack ADSR Module
• 555 Based design
• Benjie Jiao MiniADSR
  • Original was based on Barry Klein design
  • As built by schmitzbits design - "The Fastest Envelope in the West"
  • A, D, and R Pots should be log pots
• Pot silkscreen should show DECAY not DELAY

ER-CV-POTS-5 - Eurorack Control Voltage Pots

• Provides 5 Control Voltage Pots for manual control and testing of CV inputs
• Use SYNTH-MIXER6-01 card with rework
  • Do not install Opamp
  • Do not install any passives
  • Clip J2-J7 tip switch pins (edge of card) - verify grounds removed
  • Hacksaw off top of card - J1-J2, RV1-RV2
  • Cut etches from J3-J6 (tip) to RV3-RV6 (bottom pin)
  • Add wires J3-J7 (tips) to RV3-RV7 (center pins)
  • Add wire U1-7 to U1-2
  • Fill holes J8 pins 1,2
  • Install 2x4 header in J8 (pins 3-10)
  • P-Touch labels
    • Label over top 2 holes "CV-POTS-5"
    • Relabel next 5 holes as CV1-CV5
      • Blank label over bottom 2 holes
    • Label end of J8 "CV+"
• Re-build as 4 channels on ER-PROTO-01
  • Buffer outputs with Op Amps
• Could power from either 5V or +/-12V

ER-MIDI-CV4-02 - Eurorack 4X CV Module

ER-MIDI-CV4-02

• Eurorack 6HP, 3U module
• Adapted from HAGIWO's MIDI to CV module
  • Translate from Japanese to English using browser
  • Removes Digital Outputs
  • Has 4 Analog Outputs instead of 2
• Based also on SYNTH-MIDI-CV4-01
• Arduino Pro Mini
  • 16 MHz
  • 5V
  • Could cable using external FTDI USB to Serial to get USB MIDI
• MIDI In on TRS Type A jack
• (4) 0-5V Analog CV outs
  • MCP4822 12-bit D/A - SPI Interface
    • MCP4822 Datasheet
  • Use with ER-VCO-03
    • CV_1 = V/OCT
    • CV_2 = MOD
• GATE output
• CLK output
• TRIG output
• Standard EuroRack 16 pin header

ER-MIDI-THRU - Eurorack MIDI Thru

ER-MIDI-THRU

• MIDI In on DIN-5 or 3.5mm TRS Type A
• 4 Channel MIDI outputs on 3.5mm TRS Type A
• Activity LED
• 6 HP wide (30mm)
• 3U tall
• Eurorack power jack
  • Uses 5V

ER-MIXER5-01 - Eurorack 5 Channel Mixer

ER-MIXER5-01

• Eurorack 6HP
• Adapted from HAGIWO's 5 Channel Mixer Module
• Separate individual input pots and output pot
• Use A taper pots to mix audio signals
• Use B taper pots to mix control voltage signals
• Views: Front Panel, Front (controls), Parts side

ER-MIXER5-02 - Eurorack 5 Channel Mixer

ER-MIXER5-02

• Eurorack 6HP
• Same as ER-MIXER5-01 but has 6 pots at top, jacks on bottom
• Adapted from HAGIWO's 5 Channel Mixer Module
• Separate individual input pots and output pot
• Use A taper pots to mix audio signals
• Use B taper pots to mix control voltage signals
• Views: Front Panel, Front (controls), Parts side

ER-MULTS-01

ER-MULTS-01

ER-MULTS-02

ER-MULTS-02

ER-PWR-01

ER-PWR-01

ER-PROTO-01 - Eurorack Prototype card (6 pots, 4 jacks)

ER-PROTO-01

• Eurorack Prototyping card set
• 6 HP wide (30mm) front panel
• 3U tall
• 0-6 POTS
  • Series resistors on pot wiper
  • All 3 pot pins brought to top header
• 0-4 Jacks
• Tip/sleeve brought to header near middle/bottom
• Pots on top, jacks on bottom
  • Easier to adjust pots without bumping into pots
  • Pots more often accessed than jacks
• Large prototyping area
• +12V, -12V down board edges
• 5V/GND down center of card
• Bussed connections horizontally
• Front Panel with generic labels
  • Cover with White on Black P-Touch labels

ER-PROTO-01 - Examples

Arduino NANO MOZZI

Arduino NANO MOZZI on ER-PROTO-01

CV4 - 4 Control Voltages

ER-CVPOTS4

Noise Generator

Noise Generator on ER-PROTO-01

Slew Rate Controller

Slew Rate Controller on ER-PROTO-01

ER-PROTO-02 - Eurorack Prototype card (6 pots, 6 jacks)

ER-PROTO-02

• Eurorack Prototyping card set
• 6 HP wide (30mm) front panel
• 3U tall
• 0-6 POTS
  • Series resistors on pot wiper
  • All 3 pot pins brought to top header
• 0-6 Jacks
• Tip/ring brought to header near bottom
• Pots on top, jacks on bottom
  • Easier to adjust pots without bumping into pots
  • Pots more often accessed than jacks
• Large prototyping area
• +12V, -12V down board edges
• 5V/GND down center of card
• Bussed connections horizontally
• Front Panel with generic labels
  • Cover with White on Black P-Touch labels

ER-PROTO-02 - Examples

Cards built on the PROTO-02 card set

ER-BEZIER-CV

• ER-BEZIER-CV - Random Control Voltages (CVs)

ER-CV-AMP3

• ER-CV-AMP3 - Amplify CVs or GATES by 2

ER-DELAY-01

• ER-DELAY-01 - Echo

ER-DELAY-02

• ER-DELAY-02 - Echo

ER-GATE-SEQ-01

• ER-GATE-SEQ-01 - GATE Sequencer

ER-LEDS

• ER-LEDS - Control a NeoPixel strip

ER-MOZZI-DB - Arduino NANO running MOZZI

ER-MOZZI-DB

• Daughtercard to ER-PROTO-02 card
  • Uses Front Panel and Controls card
    • Controls card populated as required
      • 0-6 Jacks, 0-6 Pots
• Arduino NANO
• High Def Sound output
• Up to 6 Pots connected to A/D inputs
• Up to 4 input jacks connected to A/D inputs
• Options
  • 0-4 Pots, 0-4 Input Jacks
  • 5 Pots, 0-3 Input Jacks
  • 6 Pots, 0-2 Input Jacks

ER-MOZZI-DB-03 - Arduino NANO running MOZZI

ER-MOZZI-DB-03

ER-MOZZI-DRUMS

• ER-MOZZI-DRUMS - Drums module

ER-SCOPE-01

• ER-SCOPE-01 - Scope

ER-SH-02 - Dual Sample and Hold

ER-SH-02

CV SHIFT on ER-PROTO-02

CV SHIFT on ER-PROTO-02

ER-STIX

ER-STIX - Mutable Instruments Branches "like"

ER-USB-MIDI

ER-USB-MIDI - USB MIDI to TRS A

ER-VCA2-01 - 2 Channel Voltage Controlled Amplifier

ER-VCA2-01

• Dual VCA
• Adjust between VCA and Mod
• 3U tall
• 6HP wide
• 3 card set
• LM13700 based
• Eurorack
• +/- 12V Power, 10-pin power connector

ER-VCF-02 - Voltage Controlled Filter

ER-VCF-02

• 3U tall
• 6 HP (30mm) wide
• Uses ER-PROTO-02 controls cards
• Tommy Killander Design
  • Low pass only version of Moritz design
• Video

ER-VCO-03 - Eurorack VCO using RP2040 CPU

ER-VCO-03

• Eurorack 6HP
• (3) Card set
• Views: Control Panel rear side, Control Panel controls side, Logic card component side, Logic card rear side, Front Panel

Eurorack DIY Panel

• Front/Back View
• Left = top

• Based on HAGIWO design

• 6HP wide
• 3U tall
• Power and Ground bus on either side of the card
• Reduces wiring
• Slotted mounting holes
• 5mm Grid on rear side makes it easier to locate connectors for drilling

Eurorack +/- 12V Power Supply

• 115VAC in, 24V CT, 24 VA Transformer
  • 12*1.414 = ~17V
    • Leaves 5V for regulator headroom and ripple
• L7812CV, +12V, 1.5A Regulator
• L7912CV, -12V, 1.5A Regulator

HAGIWO Builds

• HAGIWO on Reddit
• Repository of HAGIWO's DIY Modular Synth Summary
• Mapping of Land Boards Synth cards to HAGIWO designs
  • Purpose is re-use of Land Boards card elements for HAGIWO designs

FUNCTION	3.5MM	POTS	TOGG	PBS	ROT	DIN5	PROCESSING	LINK
No. 59 CV Adder	12	0	0	0	0	0	NONE	https://note.com/solder_state/n/nd040f097cbc2
No. 58 Bezier CV	2	4	0	0	0	0	NANO	https://note.com/solder_state/n/n39aacefd73a3
No. 57 Strain CV								https://note.com/solder_state/n/n79cdb2c458a9
No.56 Sample Drum	3	1	1	0	0	0	ESP32C3	https://note.com/solder_state/n/n950ed088c3cb
No.55 V2164 Dual VCA	6	6	0	0	0	0	NONE	https://note.com/solder_state/n/nd82c027d0597
No.54 PT2399 clock sync delay	4	3	1	0	0	0	NANO	https://note.com/solder_state/n/nf6dc0a61e26d
No.52 Reverse step sequencer	4	8	2	0	0	0	CDT7350	https://note.com/solder_state/n/n13c49f08ca1f
No.50 LFO/VCO rebuild	2	3	1	0	0	0	NANO/AD9833	https://note.com/solder_state/n/nd2c22a73e8fe
No.49 Clock Divider	11	0	0	0	0	0	TC4040BP	https://note.com/solder_state/n/n7979cda44dcb
No. 47 Sample & hold	3	2	1	0	0	0	LF398	https://note.com/solder_state/n/n29b52f4f01f1
No.46 Dual Envelope generator	4	8	0	0	0	0	NANO	https://note.com/solder_state/n/n6fb73eb1d8b8
No.45 Diode clip Distortion	2	3	0	0	0	0	NONE	https://note.com/solder_state/n/n5f35e2e84a3e
No.44 Wave shaper & VCA	2	1	0	0	0	0	NONE	https://note.com/solder_state/n/nfdc2e198255a
No.43 Envelope Follower	4	3	0	0	0	0	NONE	https://note.com/solder_state/n/n110e9ba066b3
No.42 PCM drum	6	4	2	1	0	0	NSX-1/SAMD	https://note.com/solder_state/n/neabe7e014c11
No.40 Voltage controlled switch	8	1	0	1	0	0	NJU211	https://note.com/solder_state/n/n98883e71f814
No.39 Diode ladder VCF	3	3	0	0	0	0	NONE	https://note.com/solder_state/n/n598f23105ec4
No.38 Touch controller	5	1	1	4*	0	0	NANO/MPR121	https://note.com/solder_state/n/ncd42925f726b
No.37 Overflow folding VCO	4	3	0	1	0	0	XIAO	https://note.com/solder_state/n/nf01e7c92b010
No.36 LM13700 Dual VCA	6	2	0	0	0	0	LM13700	https://note.com/solder_state/n/n3357199504d8
No.35 CV to MIDI	6	1	0	0	0	1	NANO/SSD1306	https://note.com/solder_state/n/nb618127f37c9
No.33 Dual Quantizer	7	1	0	0	1	0	SAMD/SSD1306	https://note.com/solder_state/n/nb8b9a2f212a2
No.32 Spin FV-1 multi FX	5	5	0	0	0	0	NANO/FV-1	https://note.com/solder_state/n/n1c402a78a0fe
No.31 Ring modulator & wavefold	4	3	0	0	0	0	AD633	https://note.com/solder_state/n/n9d138d74b39d
No.30 Euclidean rhythm sequencer	7	0	0	1	1	0	NANO/SSD1306	https://note.com/solder_state/n/n433b32ea6dbc
No.29 SH-101 type sequencer	7	1 TRIM	0	1	1	0	SAMD/SSD1306	https://note.com/solder_state/n/n80f4baf81226
No.28 DSP multi effector	2	0	0	0	0	0	DSP	https://note.com/solder_state/n/nd9c984a9ab7a
No.27 5ch mixer	6	6	0	0	0	0	NONE	https://note.com/solder_state/n/nffc1a33053be
No.26 V2044 VCF	3	3	0	0	0	0	V2044 VCF	https://note.com/solder_state/n/n0fabdc23fe1e
No.25 Oscillo scope & Spectrum analyzer	3	1	1	0	1	0	NANO/SSD1306	https://note.com/solder_state/n/n6b4cc8d1c6b9
No.24 V2164 Dual VCA	6	2	0	0	0	0	V2164	https://note.com/solder_state/n/n14a8be5f7118
No.23 CHORD VCO	4	3	0	0	0	0	NANO	https://note.com/solder_state/n/n681d2e07e324
No.22 Additive VCO	4	3	0	0	0	0	NANO	https://note.com/solder_state/n/n30b3a8737b1e
No.20 CV/GATE 8step sequencer	3	8	1	0	0	0	CD4022BE /NE555	https://note.com/solder_state/n/n4da93d157f26
No.19 FM VCO	4	3	0	0	0	0	NANO	https://note.com/solder_state/n/n88317851a4c7
No.18 2OSC VCO	3	3	1	0	0	0	NANO	https://note.com/solder_state/n/n71c67b5aaeca
No.17 Multi mode Envelope generator	2	4	1	0	0	0	NANO	https://note.com/solder_state/n/n69643b792274
No.16 CV/Gate sequencer & Arpeggiator	5	0	0	1	1	0	NANO/SSD1306	https://note.com/solder_state/n/n7c2809976698
No.15 TR-808/909 sample player drum	5	0	0	1	0	0	SAMD/SSD1306	https://note.com/solder_state/n/n0209d16d0d08
No.14 KICK	3	4	0	0	0	0	NANO	https://note.com/solder_state/n/ne33e32660d50
No.13 Noise & Hi-hat	4	3	0	0	0	0	NANO	https://note.com/solder_state/n/nf65437f12790
No.12 Clock SYNC LFO	2	4	0	0	0	0	NANO	https://note.com/solder_state/n/n4c600f2431c3
No.11 MIDI to CV	4	1	0	0	0	1	NANO	https://note.com/solder_state/n/n17e028497eba
No.10 Gate Burst/Delay	4	2	1	1	0	0	NANO	https://note.com/solder_state/n/n28b5c43229af
No.9 6ch trigger sequencer	7	0	0	1	1	0	NANO/SSD1306	https://note.com/solder_state/n/n17c69afd484d
No.8 SX150 VCF	3	2	1	0	0	0	NANO/MCP4726	https://note.com/solder_state/n/n5136d98930a8
No.7 Quantizer	4	2	1	0	1	0	NANO/MCP4726	https://note.com/solder_state/n/nde97a0516f03
No.6 Clock multi divide	4	2	1	0	0	0	NANO	https://note.com/solder_state/n/n8907f2f6e8f5
No.5 Generative sequencer	3	2	1	0	0	0	NANO/MCP4911	https://note.com/solder_state/n/n8a489f0b857a
No.4 samplar	3	1	1	0	1	0	NANO/TF PLAYER	https://note.com/solder_state/n/n6057a5256042

Eurorack Reference Docs

• Doepfer Eurocard inventor/specs
  • Principles of Voltage Control
• MIDI Communication
• Creative Control Strategies: MIDI to CV
• EuroPi
• Eurorack Beginners Guide
• Eurorack Wiki page
• KiCad Audio Jack Symbols
• MidiSoft
  • EuroRack Dimensions
  • Panel Holes
• A simplified guide to TRS MIDI
• How to Make Your Own 3.5mm mini stereo TRS-to-MIDI 5 pin DIN cables
• Eurorack Power Connectors
• MIDI Electrical spec
• Eurorack Facebook group

Projects

• elkayem midi2cv GitHub page - Nano based project
  • Arduino MIDI library has not yet been ported to Pico so will need to use Python
  • Drives 4 CV outputs: Pitch Blend, Control, Note, Velocity
  • This card only drives Note (Voltes/Oct, Mod)
• PicoPicoSynth
• Deftaudio GitHub - KiCad footprints
• Turing Machine
• Simple DIY Electronic Music Projects - diyelectromusic
• DIY Hackable Arduino Drum Machine
  • vIDEO
• Build the Auduino Granular Synth
• Benjie's Synth DIY notes - Nice docs
  • Benjie Jiao - DIY Modular Synth Project - YouTube channel
• REDDIT Synth DIY
• tkilla64 Nice collection of Eurorack module designs - mostly Gerbers
• Scott Billingsley Philosophy of Noise - GitHub Repo
• Andrew Kilpatrick DINTREE GitHub
• Mutable Instruments Schematic PDFs
• Music From Outer Space
• Kristian Blåsol's Modular in a week]
  • Kristian Blåsol's Modular in a week - YouTube channel
  • Sourcery Studios Tindie Store
  • Sourcery Studios Discord channel

KiCad Libraries

• Ben Jiao Modular KiCad Libraries
• graybloomfield - Very nice Arduino based designs
• Winterbloom KiCad Library
• Using Python to vectorize artwork for PCBs

Daughterboard Heights

• From notes on How to Make Great Looking Modular Front Panels - Part 3 Module Circuit Board Layout
  • The absolute maximum of other boards I've seen is 111,5 mm and the TipTop Happy Ending Kit offers a space of 112,5 mm
• 114.8mm measured between 3U Synthrotek rails
  • 128.5mm - 114.8mm = 13.7mm both sides, 6.875mm per side
  • 111.5mm daughtercard, leaves 8.5mm clearances top/bottom

Part Orientations

• For pots with built-in pointers, pot pins go down for pointer to go up at center (up) point

Front Panel Jacks

• Eurorack Panel Jacks

Eurorack Vertical Pots

• Eurorack Pots

Op Amps

• From this site
  • The TL084 Op-Amp is very similar to TL074 but has high noise immunity and better offset characteristics.
  • The TL074 has lower noise figure, so is better for AC signals.
  • The TL084 has lower offset, so is better for DC signals.
  • The TL084 has better DC performance (low offset) and the TL074 has better noise/distortion performance.
  • You can use TL074s on the audio paths, TL084s on the control paths.
  • TL074 Datasheet
  • TL084 Datasheet
• The TL074 is $0.75 in qty 10 (on Mouser)
• The TL084 is $0.55 in qty 10 (on Mouser)
• The TL072 and TL082 are both about the same price as each other, but are more expensive than the quad parts

Module Kits

• Erica Synths
  • Erica Synths DIY GitHub
• SyntherJack - DIY Synths
• BEFACO - Kits
• Kassutronics DIY Store
  • Kassutronics DIY GitHub
• synthCube MFOS PCBs
• Thonk Shop - in UK
• synthrotek
• TuringMachine Mark 2

Erica Synths EDU DIY Sequencer Build Notes

• EDU DIY Sequencer
• Assembly drawing unreadable line weights when printed out
  • Needed to zoom way in on PC to PDF
• Ref des of parts not in any particular order
  • A break-out drawing pointing to Find Numbers would help a lot
• No real PL
  • What is called a PL does not list ref des
• BC548 in design. BC547 was shipped
  • BC547 is a better spec part (same function, higher voltage version)
• Transistors pad sizes way too small
• Resistor holes are very big compared to 1/4W lead diameters
• Getting to the legs of the LEDs was challenging
  • Soldering was not trivial but was the least of the challenges
  • Trimming the legs near the transistor was scary
  • Could not cut one low due to nearby parts
• Toggle switch has very large holes that make alignment of the switches very difficult
• Clock In voltage needs to meet CD4000 expected level ~70% of Vcc or about 8V
  • My 5V clock didn't work
    • Replacing the clock unity gain with a comparator might be a good choice, but would create a 12V clock out from a 5V in clock
• Trimmer 2K was 2K5
• Unable to get trim all the way to 5V or 2.5V
  • Video has same issue but just w/ 5V
  • Probably not a big issue and might just be "safer"
  • Got closer to the 2.5V position
• Switches don't turn off the CV, they just shut off the gate
  • Need an Envelope Generator to test
• Holes to mount in rack are round - slotted would be better possibly
• All in all, good value for the money

Braids Throughhole version of the Mutable Instruments Braids

• Through-hole Braids

Sorcery Studios Beaks, a throughhole PWM version of MI Peaks

• Beaks Through Hole Peaks

Sorcery Studios POW - Power Module

• POW - Modular Power Panel - Tindie page

Sorcery Studios GRIS - Drum Controller

• GRIS - Through-hole GRIDS

Software

• adafruit_midi CircuitPython API
  • Example code
• MIDI Controller in Python
• USB to Serial MIDI
• MidiEditor
• Convert binary files to C data arrays (Arduino) - In Japanese
• Binary to C Array
• Arduino Mozzi Library
• esp32_basic_synth
• esp32_usb_midi
• arduino_midi_library
• Pico MIDI Host to MIDI UART Adapter

Hardware/Parts

• Synthrotek Store
• THONKICONN – 3.5MM JACK SOCKETS
• Potentiometers are usually marked with an "A" for logarithmic taper or a "B" for linear taper;
• RV09AF vertical mount is Alpha pot part number
• 9mm Pots
• Tayda 3.5mm Jacks and stuff

Samples

• Drum Samples

Box Build

Box Version 2

Eurorack Box Build V2

• 104 HP
• Two 3U rows
• 1/2" Cherry
• Spar varnish finish

Box Version 1

Eurorack Box Build

• 3/4" Red Oak plywood
• Spar varnish finish (no finished in photo)
• 84HP
• Single 3U

Videos

• Hooking together modules