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Modular Synth (Eurorack) - DIY Modules

DIY Modules

I decided to build a number of DIY modules: (As of 11/04/21, I have built 200 DIY modules).

Mutable Instruments CVPal (USB Midi to CV)

22/04/17 Based on cost and simplicity I built a Mutable Instruments CVpal. This has some limitations - only 5V CV and no MIDI clock. It also has latency issued under Windows but is fine on Mac and iOS. But it was cheap and will get me started!

Works really well and tracks well.

16/01/21 Built another one (changed the name in the code so I could use it on the same machine as the first).

No issues with the build.

Three Frequency Central VCOs (Roland System 100 clone)

15/08/17 I built two FC VCOs with the heater boards

16/08/17 I also bought (dirt cheap) a non-functioning VCO from a forum that I will fix (it was cheaper than the faceplate on its own! One of the transistors was soldered in the wrong orientation. A quick swap and it worked fine.

Looking at the schematic it looks really similar to the Doepfer a110-1 (it sounds really similar).

Great sound. They track well over four octaves and seem stable on long sessions. They also go very low so double up as LFOs.

Frequency Central ADSR (Roland System 100 clone)


Worked straight away at power up. Great envelope generator - may have to build another one !

25/10/18 I did build another one ! (Very painless and easy build - no issues).

NLC Double LFO

E:\My Documents\Andy\WWW\Luthiery\site5\modular\images 16/08/17

Had a few issues with this build - one of the jacks was shorting a resistor (which was located underneath the jack !) One of the LFOs was giving a mix of both LFOs. Also the LED wouldnt light up - worked when I reversed it (although that meant inserting it on the PCB opposite to the polarity marked on the PCB !) All working now though.

Frequency Central Vogue Filter (Moog Rogue clone)


Really nice sound - very vintage. Love it !

Frequency Central Sample and Hold / Noise


Really impressive module - quite deep and you can do an awful lot with it.

Two NLC Sloths (chaotic slowly evolving modulation)

24/08/17 I decided to build two of these for modulating slowly evolving patches.

The x-y scope demonstrates the strange attractors. I tried using toner-transfer to make the front panels - needs a little practice!

Passive Multiple


Simple passive multiple. Bought the panel for 1.75 (!) from the pusherman group. I wired it as either 2x one-to-three or 1x one-to-seven (depending on whether the jack into the fifth socket is inserted or not). 22/01/20 Built three more.

MI Ripples Filter

10/02/18 Scary small pitch SMT (0603) - resistors the size of about 2 grains of sugar! I spent ages summoning the courage to start soldering SMT. I decided to get lots of magnification and try soldering with a normal iron. After trying different tips, I settled on the tip I usually use for through-hole as it got lots of heat to the soldering point in a very short space of time. Using really fine tips took too long to heat up the pads. I did use very fine solder though (0.4mm diameter). I used lots of flux which really helped.

I bought one board from and one from the pusherman facebook group (much cheaper !). I wanted to check if there were any quality differences before soldering more complex boards. They both seemed equally good.

The silver panel is a Greyscale panel (bought secondhand from the muffwiggler board) and the black panel is from pusherman.

The boards were surprisingly easy to build. Initially neither worked. The purple board had a cold solder joint on one of the opamps. A quick reflow and it was working perfectly. The black board was a pain to debug. It needed lots of probing with an oscilloscope and multimeter and hours of poring over the schematic ! In the end one of the resistors in the filter cascading circuit was open circuit ! (I hadn't heated it much at all so I have no idea why it was dead). After swapping it out the filter worked perfectly.

The following photos show the build process (the oscilloscope is showing the VCA working correctly).

23/08/19 Built another two!

No issues with builds - nice and straight forward.

O+C CV Utility Module

24/02/18 Ornament and Crime is a multipurpose module for generating CV. It only exists as a DIY module. It uses a more managable size SMT (0805). It is based on a Teensy 3.2 Arduino board and runs firmware inspired and adapted from multiple sources (quantiser, Turing Machine, various Mutable Instruments modules).

It was a fairly straight forward build and worked on power up. The image below shows the AD generator (Piques, adapted from the Peaks firmware) running in the oscilloscope trace.

09/01/19 I built another o_C

Easy build with no issues, other than the upper switch had an issue in that the upper connectors should have been in continuity but weren't so I just quickly jumpered them.

19/11/19 Built another one - a micro version, this time.

No issues with the build.

4xVCA (0603 Conversion of Mutable Instruments Veils)

01/03/18 Built two 4xVCA modules

These were 0603 conversions of the original 0402 Mutable Instruments Veils module. PCBs and panels bought from the facebook group, Pusherman. These were quite tricky to build - 0603 SMT with tiny opamp packages. The PCB was quite compact! Surprisingly the first one worked first time after a few false starts due to potentiometer pins not making a good contact (when only pushed in, not soldered in order to test it). The second one was much more of a pain: a few cold solder joints around the opamps were quickly sorted. The real difficulty was tracing a bridge to the ground plane from one of the pads of a resistor (that shouldnt have been in contact with ground !)

Passive Attenuators

08/03/18 Panel cut from aluminium blank and wired point-to-point.

Mutable Instruments Braids

21/03/18 First attempt at soldering STM32 microcontrollers (tiny pitch SMT). It all went pretty well. Only one hiccup on the build - I soldered a capacitor in at 90 degrees on both boards - spotted it straight away and removed them with hot air. The flashing was painless. On startup one board worked perfectly first time - all tests ok. On the other board the display was screwy - I had a cold solder joint on one leg of one of the shift registers - very quick fix.

The encoders I used send a reversed signal compared to the factory encoders (Bourns vs Panasonic), so I needed to modify the source code and recompile the firmware to enable the correct direction of the encoders. (The releavant file is drivers/encoder.h and four lines need changing).

Sounds amazing and surprisingly painless builds !

23/04/18 It's so good, I built another one! (Partly so I could set up drums easily).

Very straight dorward build. Power section had no problems. Flashed immediately within the Mutable dev environment. Fired up fine. The only issue was no audio. A quick trace with the oscilloscope showed signals going from the STM to the DAC but no onward audio. A quick look at the schematic and it showed pins 3 and 4 should be bridged. Tapping both with the scope probe produced audio. A closer inspection showed pin 4 to be slightly raised off the pcb and not making contact. A quick bend with the tweezers and a dab with the solder and it was up and running.

Ken Stone's CGS60 Stomp Box Adapter

02/04/18 Eurorack modular synths have a much higher voltage than typical guitar effects pedals so they need attenuation before feeding a signal into a pedal and then amplification of the resulting signal back up to modular levels. The CGS60 Stomp box adapter has 20x attenuation and then 20x amplification. I had enough spare parts for a stripboard build. I could fit two channels into 8hp. It worked perfectly straight away.

Mutable Instruments Peaks

12/04/18 PCB and panel bought x3. Initially I built two of them. I built and tested the power section first. One of them had a cold solder joint on the 2.5v voltage regulator. I then soldered the STM32s and flashed them. One wouldn't verify. On inspection there was a tiny bridge which was quickly sorted. It then flashed fine, using the Mutable Instruments dev environment on a Mac. The rest of the build was straight forward with no other errors.

I have another board and panel to build another one at some point in the future!

The only issues with the builds was setting the zero offset in firmware. This is a hidden mode entered by pressing one button on boot up. I just could no enter it at all. I set up the debug client and server and peeked around in gdb. It all looked good, just wasn't registering the button. I think it was the debounce code not registering it. In the end I just set a breakpoint after the check and poked the right bit so that the check passed. Continuing on with the code meant I could easily calibrate both modules fine.

To calibrate using openocd, run the openocd/gdb code - in one window run the openocd debug server; in another window run the debug client. Set a breakpoint on or about line 74 in Do a reset and init ("monitor reset init"). Set the "calibrating_" variable to "true" after the check and then continue. The module will enter the calibration routine and for each channel, one pot controls coarse offset and the other controls fine offset.

28/05/18 A month later I built another one. I flashed this with a hacked version of Dead Man's Catch alternative firmware, modified to include the latest factory Peaks code, along with software calibration. I needed to use openocd again in order to calibrate the zero offset.

12/09/19 Built another one to use as a testbed for some firmware ideas I am playing with.

Easy build. I added a Lorenz attractor and a Rossler attractor to Dead Man's Catch firmware. In due course I'll add more chaotic functions.

07/08/20 Built two more.

No issues with the builds.

Mutable Instruments Branches

22/04/18 Built two MI Branches. (PCB and panel bought x3).

Very easy builds. No issues at all.

It's worth making a note for the future about flashing them. I used an Olimex AVR-ISP-MkII. I had a real pain trying to get it to work on a Mac with avrdude in the Mutable dev environment. I tried it on a PC using Atmel Studio and it worked fine. I know I had to change the firmware for it to work with avrdude so I used Atmel Flip to do that which was straight forward. However avrdude still wouldn't read it. I saw that some people had had problems with avrdude 6 (used in the mutable dev environment), so I downloaded the avrdude 5.9 sources, installed the dependencies (usblib, yacc, etc) and compiled it. Hooray, it worked. Unfortunately avrdude 5 config file didn't have the m88p config. So I copied it from the avrdude 6 config and pasted it into the v5 config file. After that, it all worked trivially easily. To flash using the dev environment then use make as usual but pass the variable AVRDUDE with its location, eg "make -f branches/makefile AVRDUDE= bootstrap_all"

27/12/18 Built another MI Branches - using up spare parts !

Quick and easy build with no issues.

Mutable Instruments Grids

04/05/18 Built two MI Grids.

This would have been a nice straight forward build if I hadn't decided to try to program one late at night after going to the pub ! I think I bricked one of the MCUs when programming it from Atmel studio (I decided it would be a good idea to use this software for some reason !) I think I must have set the wrong fuses. I tried reflowing the crystal (removed it to check for bridges/problems) and it was fine. In the end (probably a bad beer-influenced decision) I removed the MCU with hot air. This meant I needed to buy another one on my next Mouser order. This time there were no issues programming it from the Mutable Dev Environment. There were also no soldering issues and it worked first time.

06/01/19 Completed another Grids - I had all the spare parts apart from two opamps so decided to build another Grids.

No issues with the build. Worked first time.

Mutable Instruments Module Tester


Flashed and built the firmware from within the Mutable Dev Environment. Very painless and straight forward build.

Mutable Instruments Links

04/05/18 Built two MI Links.

Both were quite fiddly builds with all the passives and ICs quite close together. However, they both worked perfectly first time with no errors.

Mutable Instruments Tides

07/05/18 Built two MI Tides.

Above photos: panels and pcbs, large pile of components, power section complete and tested, STM32 MCU and associated decoupling caps installed and connecting the STLink2 programmer, flashing the MCU, jacks and pots inserted but not soldered, testing, completed.

Both worked perfectly first time, with no issues.

Mutable Instruments Elements

30/05/18 Built an MI Elements.

The above images show the: bare pcb and panel, the power section built, the microprocessor soldered, flashing the microprocessor, finished soldering the surface mount components, testing all the inputs and outputs before soldering the through hole components, and the completed module.

It was a surprisingly easy build with lots of space and it all worked first time on power up with no issues. It sounds very nice !

Mutable Instruments Shades

01/06/18 Built two MI Shades.

Very quick and straight forward builds. One worked perfectly straight away. On the other one the second and third channels weren't working initially. I had a couple of dry joints on two opamps that was a pretty much instant fix. (Initially the iron wasn't heating the joints well - the tip wasn't well-tinned and I think that was the problem with those op-amps).

Very useful modules - offset/attenuator/attenuverter/mixer.

Mutable Instruments Ears

05/06/18 Built three MI Ears.

I ordered an 0603 version of Ears with matching panels from (The factory Mutable Instruments version is 0402).

The images above show: the bare boards and panels, surface mount parts soldered, the completed module, testing the gate output with external audio, testing the contact mic and finally the three modules completed.

Straight forward builds. I substituted 1n5819 diodes for PMEG2010AEBs as I didn't have any. I had to stack two 0603 470n caps in parallel as I didn't have any 1uF caps of suitable voltage. Would have worked first time if I wasn't such a numpty and used 6v "special" lm324 opamps instead of general purpose ones !! (Who needs LEDs when ferrite beads glow so pretily). A quick hot air rework and they were swapped out. They then worked fine with no issues.

22/10/18 I thought I'd build one more so I can have one on each channel of a four channel polyphonic voice:

Passive Attenuator

05/06/18 Built two Pusherman Levels: 4-way, 4hp passive attenuator.

Not much to say. Trivial builds. Makes things quieter !

27/09/18 I built another one. This had an error on the pcb. One of the tracks from the input of channel 2 was shorted to the pot of channel 4. I broke the track and jumpered it with a cut off piece of a through hole passive.

Mutable Instruments Warps

15/06/18 Built an MI Warps.

Straight forward build with no issues. Images show: bare pcb and panel, power section built and tested, MCU and associated components soldered, flashing the MCU, module completed apart from control hardware, control hardware placed but not soldered, testing the module, the finished module.

15/12/18 Built another MI Warps.

Straight forward build with no issues (worked perfectly straight away). I used the parasite alternative firmware for this module. The firmware doesn't have the normalization probe calibration code, so I added this to the parasite firmware, which works well. The files can be found on my parasites github.

27/10/19 Built yet another MI Warps!

This was a module that had most of the SMT parts already assembled - a friend did a run of pcba (pcb assembled) pcbs - I was ofered this at a ridiculously cheap price (thanks!) Way too good to refuse - I needed to swap a few capacitors and then it was working with no issues.

20/06/20 Built yet more MI Warps!

No issues with the builds.

Mutable Instruments Kinks

17/08/18 Built three MI Kinks.

Images show: bare pcbs, 0402 resistor size, populated boards, testing and then the completed builds.

These modules use teeny, tiny 0402 surface mount parts (see photo above of a resistor with my manky thumb for reference ! I was quite nervous before starting these as they are very closely populated boards with tiny parts - the diodes are really fiddly and very tricky to see the stripe which marks polarity. For these builds I still hand-soldered them with a soldering iron and solder. I did consider using solder paste and reflowing with either skillet or hot air but decided to stick with a soldering iron, which I'm glad I did.

Apart from the eye-strain, these were reasonably straight-forward builds in the end. All three had issues in testing: the tl074 opamps all had dry joints on some of the legs (strangely the opa4171s were all ok). These were pretty easy to sort out - just touching up the opamp legs. After that they worked fine.

Mutable Instruments Yarns

21/08/18 Built two MI Yarns.

Images show: bare pcbs, pcbs with the pile of parts, power section of the boards populated, MCU and associated parts installed - front, MCU installed - rear, flashing the MCU, completed build - front with no face plate, completed build - rear, completed build, calibration (more than 1/1000 cent accuracy in this image!).

Straight forward builds. Only one issue - on one of the modules the display didn't fire up initially (I had wondered if I had a questionable short on the MCU but it looked ok visually so I had left it - it was on the display data pins of the MCU so I quickly reflowed that pin and it worked perfectly straight afterwards. I had bought encoders that were reversed (compared to the factory modules) - intentionally as that was what was available. I needed to make some changes to the source code to change the direction of the encoders which was trivial (and indeed I had made those changes before startiung the build).

Mutable Instruments Streams

01/09/18 Built an MI Streams.

Images show: bare pcbs, power section populated, MCU and associated parts installed, flashing the MCU, completed build - all surface mount parts placed, completed build - all through hole parts placed as well as the led level metering sub-board, testing the module, completed module.

Fiddly but straight forward build. The main hassle was cutting down the surface mount socket mount to fit the sub-board assembly. The module worked first time with no remedial work needed.

22/12/19 Built another one

No issues with the build. Worked first time.

Mutable Instruments Frames

08/09/18 Built an MI Frames.

Images show: bare pcbs, power section populated, MCU and associated parts installed, flashing the MCU, completed build - all surface mount parts placed, completed build - all through hole parts placed, testing the module, completed module.

Pretty straight forward build. I had two issues: I missed a bridge on the DAC (that was simple to fix) but there was an issue with the addition of the keyframes - the frame light stayed on a long time and seemed inconsistent. I worked out it was a dry joint on the ADC pin of the frame pot. It took at least an hour to work out if it was not working correctly and then what the problem was! After that it worked perfectly.

22/08/19 Built another one !

No issues with the build - easy and worked straight away.

Minx - Buffered Multiple (Based on Mutable Instruments Links Buffered Multiple Circuit)

11/09/18 Built an own-design buffered multiple.

PCB and panel bought. However, looking at the schematic, there was an error. The output resistor is included in the feedback loop, leading to the possibility of opamp oscillation in the presence of a capacitive load (eg with long patch cables). For peace of mind, I decided not to build it and used the parts to build two Links modules instead.

I came back to this (28th August 2018) and spent a few hours laying out a circuit and pcb based directly on the buffered multiple part of Links (with normalled connections between groups). I sent the pcb off to (a Chinese pcb manufacturer) and am awaiting 5 test boards. I have enough parts to build three of them if I want.

On the first run of pcbs, I made a mistake in Eagle and didn't create vias to join the ground planes front and rear, so needed to join up three islands of ground. Works perfectly when that is done. (The image showing the module being tested with the oscilloscope has a 'Y' offset on the scope to see both traces clearly - it's not a voltage offset !)

02/10/18 Built another two own-design buffered multiple. I corrected the Eagle files and have bought some more test boards.

Modules work perfectly - very straight-forward builds. The files can be found on my github.

Mutable Instruments Clouds

22/09/18 Built two MI Clouds.

Images show: bare pcbs, power section populated, MCU and associated parts installed, flashing the MCU, completed build - all surface mount parts placed, completed build - all through hole parts placed, testing the module, completed module.

Both worked immediately with no issues.

Buranelectrix Dredrum

27/09/18 Built three Buranelectrix Dredrums.

After testing one of them, I built the other two:

Worked perfectly first time. To compile the firmware I needed to change the source code change as well as change to the avr-gcc flags to enable compatability with latest avr toolchain.

Mutable Instruments Rings

07/10/18 Built two MI Rings.

Images show: bare pcbs, power section populated, MCU and associated parts installed, flashing the MCU, completed build - all surface mount parts placed, completed build - all through hole parts placed, testing the module, completed module.

Both worked immediately with no issues.

07/08/20 Built two more.

No issues with the builds.

Mutable Instruments Marbles

22/10/18 Built two MI Marbles. PCBs bought x6 from allpcb as well as the parts to build two of them. I also made my own panels for the first time!

On the newer modules (plaits, stages, marbles so far as of Oct 2018) MI ow use SWD to program the MCUs rather than jtag. I jumper the pins of the STLink V2 to the SWD pins on the board. With the STLinkV2 pin 1 (target voltage) needs to be jumpered to pin 19 (3.3v *from* the programmer. Here is how I wired the jumpers to flash marbles:

In order to calibrate the dac, edited the source code to output 1v and 3v. I then measured the 4 dac outputs for both 1v and 3v. From knowing the dac scale and offset as well as the calculated dac code to output a desired voltage I derived the scale and offset for each channel. I then hard-coded this into the firmware.

To calibrate the adc, long-press the rate and spread buttons. Feed 1v into rate input, press one of the two buttons, feed in 3v, press button, feed 1v into spread cv, press button and then feed 3v into spread cv, press button and the calibration is done.

No issues with the builds - both worked first time. It's an awesome module!

The calibration files and detailed instructions, along with the gerber files for the panel, can be found on my marbles github.

12/01/19 Built another Marbles as I had all the parts spare.

No issues with the build - worked with no problems immediately.

14/02/21 Built another Marbles as I had most of the parts spare.

Mutable Instruments Shelves

28/10/18 Built an MI Shelves.

No issues with the build - worked first time. Wishing I had built one ages ago!

I wanted another one (to use in stereo) and was going to build another (I had all the parts) but a friend did a 5-pcb pcba run and it worked out cheaper to buy a pcba module from him than to buy all the parts!

Mutable Instruments Plaits

02/11/18 PCB x4 and panel x3 bought as well as the parts to build three of them.

Straight-forward builds, no issues, worked immediately with no problems.

30/11/18 completed the last of the four.

No issues with the build - worked fine first time.

14/11/21 Built another

05/04/21 Built another four

These were from pcba boards from China - I ordered them with all the passives soldered (except two resistors). The quality wasn't great - there were a few poorly soldered resistors (dry joints) and one was tomb-stoned. I didnt spot all of the issues from inspection but they were pretty trivial to fix when testing the module. I'm not going to complain too much - the cost was about 5 per pcb assembled! (I had most of the parts spare to build them). I was going to pass on a few of the boards at cost but as there were errors I kept them for myself - I had spare MCUs for a project I am working on anyway and had all the other parts spare. Not sure what I am going to do with so many plaits though! (I can have a polysynth and drum machine just with all the plaits modules ! That's just ridiculous !)

Frequency Central Amplifier (VCA)

06/11/18 Built a Frequency Central System X Amplifier (VCA) from a PCB and I made a panel from sheet aluminium as FC no longer sell the panels.

I built my own panel (and didn't do a very neat job ! Trying toner transfer technique - I think I need to try more glossy paper next time). Straight forward build. The only issue was me being a numpty and installed the two power rail filtering electrolytics in reverse - bang! First time I've installed electrolytics the wrong way and first time I've blown up electrolytic caps! Other than that, it worked well!

Mutable Instruments Stages

10/11/18 Built two MI Stages. (PCBs and panels bought x6 from

Straight-forward builds. (Quite long and tedious though). No issues. Worked straight away with no problems.

Whilst I was working out how the firmware worked, I found the Easter Egg - a harmonic oscillator. I couldn't believe no-one else had found it before ! It sounds really good and is easy to access - just patch the two serial ports with a three pin plug. Multiple units can be chained. Needs to be power-cycled to change modes.

I have changed the firmware to allow easy mode changing for a single module but not yet added it for multiple modules in a chain.

The calibration files and instructions, along with the gerber files for the panel, can be found on my stages github.

A chap on one of the forums had built two Stages - both had multiple problems and he could not get them working. He offered me one of the modules if I fixed both. I agreed, thinking I may have to replace opamps and a DAC. In the end after copious cleaning of thick flux), one of the opamps needed taking off and repositioning, several resistors were unsoldered, several opamp legs were unsoldered and there were several solder bridges on opamps and the DAC. It took a couple of hours to fix them both and then I calibrated them. Both were working perfectly afterwards.

After a favour to a friend - he gave me a partially built Stages. It needed a bit of work (fixing cold solder joints, removing bridges, resoldering some passives as well as removing all the sliders) but after a couple of hours of work it worked perfectly!

808 Kick Drum

12/11/18 Built an 808 Kick Drum.

I bought 10 pcbs from and also ordered 10 panels from

Boom!!! Simple build. Just needed to adjust the value of the pull-up resistor on the accent to allow a nice "thump". Now responds nicely to low (eurorack levels) trigger voltage and low voltage accent (with impedance of ~1k) as well as nice and loud when no accent plugged in. I used a tl072 in the end (just used a jrc4558d initially as I had no spare tl072s at the time. I'll probably build a couple more.

Mutable Instruments Blinds

20/11/18 Built two MI Blinds.

Straight-forward builds with no issues (just a lot of passives !) Both worked fine first time.

Mutable Instruments Edges

24/11/18 Built an MI Edges.

Straight-forward build with no issues - worked fine first time. The only issue was flashing - it was a little different to most MI AVR builds. It used the PDI interface (rather than ICSP). It also didn't need the fuses setting explicitly. (Worth noting that there are two revisions of the board with different ADCs which require different versions of the firmware).

DSO150 Shell Oscilloscope

02/12/18 Built a DSO150 oscilloscope kit from Banggood with a conversion kit (panel and pcb) to mount in a eurorack case.

Painless build. No issues. Works really well - a lot better than I expected and a lot more usable than the DSO138 I built a while ago. (The green sticky tape is to hold the screen stable whilst building. In the last photo the screen is crooked - it was straightened up before putting in the rack !)

Mini Temps Utile Clock Utility Module

23/12/18 Built a mini Temps Utile clock utility module.

Easy build with no issues. Fantastically useful module - I didn't know how much I needed one until I built it! Wish I'd built one ages ago.

19/11/19 Built another one.

No issues with the build.

This Is Not Rocket Science Tuesday

24/12/18 built a TINRS Tuesday.

I bought a number of parts from aliexpress - the jacks, switches and a cheap jlink clone. I made a board to allow connection to the mini-jtag from either 20-pin or 4-pin (SWD), but in the end just used jumpers.

To flash the boards, I used the mutable dev environment and a cheap Chinese J-Link clone from aliexpress. I used openocd with the following commands:

sudo openocd -f /usr/local/share/openocd/scripts/interface/jlink.cfg -c "transport select swd" -c "set WORKAREASIZE 2048" -f /usr/local/share/openocd/scripts/target/klx.cfg

In other window:

telnet localhost 4444

In the openocd session I used the following commands:

kinetis mdm mass_erase
reset halt
flash probe 0
flash write_image erase /vagrant/AJH_Tuesday/AJHTues.hex 0x00000000 ihex
verify_image /vagrant/AJH_Tuesday/AJHTues.hex

(where /vagrant/AJH_Tuesday/AJHTues.hex is the combined bootloader and firmware).

Overall, a pretty painless build. Lots of fun to play with!

06/01/19 Completed the second one:

Initially it didn't run straight away. On close inspection there was a dry joint on the QFN MCU - it worked perfectly after touching it up with a soldering iron.

Mutable Instruments Veils

24/01/19 built three Mutable Instruments Veils (original 0402 pcbs)

No issues with the builds - all three worked first time with no problems.

Motivation Radio

02/02/19 built a Motivation Radio module (esp32-based module to communicate via MIDI and OSC via BLE or WIFI).

Straight-forward build. Working out how to set up the build environment and compile the code to target the module was more involved though !

Westlicht Per|former Eurorack Sequencer

08/02/19 built a Westlicht Per|former Sequencer.

It's a straight-forward build, well-spaced out 0603 parts but there is a high part count and the parts are pretty expensive - it's not a module to want to fail on ! The build had no issues and worked perfectly straight away. It's a really cool eurorack sequencer - very deep and impressive but still easy to use. For more information, see Performer Sequencer. When building it, it's worth using the test firmware to check all the functions are correct.

I had some issues on different power supplies (due to the slew rate of the rise of the power rails) that meant the module wouldn't immediately boot - it needed to be powered on and then off again. After trying firmware hacks to play with the brown out reset and it not helping, I added a supervisor (mic803) to hold the stm32 in reset until the power was stable.

This fixed all my problems and was pretty trivial to add (along with a 100nF cap from GND to RST).

gBiz Dervish

08/04/19 built a gBiz Dervish (Spin FV-1 DSP module)

Straight-forward quick build with no issues.

Antumbra 6MIX

09/04/19 Completed an Antumbra 6MIX

I started this module months previously. It was the only module I hadn't been able to get working correctly. I was getting high frequency oscillation at the opamps. The switches (when off) left the opamp inputs floating so any stray noise in the system caused oscillation. I had stupidly soldered all the parts so getting at it to sort it out was a pain. I had put it aside to look at later. I found a bit of time eventually to look at it properly. I ended up soldering the open poles of the switch to ground via a 100k resistor along with some feedback caps in the opamp loops, as well as adding decoupling caps from the rails to ground. This solved my problems nicely.

Mutable Instruments Tides 2

12/04/19 Built two Mutable Instruments Tides 2s

I ordered pcbs and panels the day the module was released. The parts came the next week and I built them the same day.

I edited the pcb to move the Recom DC-DC converter onto the back of the board as it is too high to fit on the front without a recess in the panel. It needed shifting over as it was quite close to the edge of the board.

0402, straight-forward build. No issues or errors with the build.

I have calibrated them, similarly to Stages.

All the files, including the panel, pcb and calibration code can be found on my Tides 2 github.

Sin Phi Miasma

13/04/19 Built a Sin Phi Miasma (clone of the Befaco Rampage dual function generator - similar to Make Noise Maths).

Straight forward build, 0805 parts. No errors or issues with the build.

4ms SMR

09/05/19 Built a 4ms SMR. I bought the pcb with the smt parts already soldered. This was a group buy with the blessing and approval of the designer.

To flash it, I compiled the latest version (5.1b2). I added the code to correctly display colours on the Kingbright LEDs used in this build (which give different colours to the factory SMR). I also built firmware to allow use of a 24 PPR encoder as well as a 12 PPR encoder.

I connected the pins as follows (see image above as well):

  • stlink v2 pin 1 to smr pin 1
  • stlink v2 pin 9 to smr pin 2
  • stlink v2 pin 20 to smr pin 3
  • stlink v2 pin 7 to smr pin 4

    Then using openocd I used:

    openocd -f interface/stlink-v2.cfg -f target/stm32f4x.cfg -c "program combo.hex verify reset exit"

    No issues with the build and it works well!

    Jinx - 4hp triple S&H

    09/05/19 Built a 4hp triple S&H 0603 module (based on the S&H section of Kinks) - own design

    I'd fancied a S&H based on Kinks for a while, similar to the buffered multiple I built, based on Links. So I knocked one up in Eagle. I decided to convert it to 0603 and mount the parts on the back to make it easier to diy and debug. It works well.

    12/08/19 Built another one!

    The files can be found on my Jinx github.

    Flight of Harmony Plague Bearer

    14/08/19 Built two Plague Bearers from pcbs and panels.

    Noise machines/filters/manglers! Easy 0805 builds with no issues.

    TINRS Wobbler

    23/08/19 Built two TINRS Wobblers

    Straight forward builds with no issues. Flashed in the same way as TINRS Tuesday.

    Fitzgreye 100m-ish Audio Delay

    30/08/19 Built a Fitzgreye 100m-ish Audio Delay.

    Cool, classic Roland, short audio delay (I used an MN3007).

    4ms SWN

    05/09/19 Built a 4ms SWN. I bought the pcb with the smt parts already soldered. This was a group buy with the blessing and approval of the designer.

    Building the firmware was non-trivial. There was a trivial bug in the bootloader that required a one-line fix. Getting a build environment that built a fully functioning firmware was tricky (some environments built a firmware that did not function correctly). I used a mac in the end. After the bootloader I needed to build one firmware (changes to lines 32 and 34 in globals.h) to write the wavetables to flash. This resulted in a slow bootup (~20 seconds). So I flashed a second main firmware that did not include the wavetables (as they were now stored).

    The pcba process was entertaining - there was a bit of guess work as to the correct parts to use - led encoders and rgb-switches. These required a large minimum order quantity.

    The quality of the pcb was pretty poor - one guy had broken traces. I had a missing resistor (R80 - see above). The boards had a lot of flux left on them and some of the holes were almost completely closed and needed opening up.

    After all this I have a lovely working module - and it's really awesome !

    CTAG Strampler

    19/09/19 Built a Ctag Strampler.

    No issues with the build. Works well for streaming and playing samples.

    MI Shruthi

    24/09/19 Built a MI Shruthi to use with my OP-Z

    No issues with the build. Works well. I definitely prefer SMT though - through hole feels so painful and slow!

    TINRS Rectangular Thing

    29/09/19 Built a TINRS Rectangular Thing to use with my OP-Z

    No issues with the build. I took my time soldering the pots and jacks - I soldered in groups by function and then tested carefully as the pots and jacks were too loose to test the module properly whilst they were only push fitted. Sorting out a soldering error on the pcb would be tricky once the pots and jacks were soldered as it was quite a tight layout for the user interface!

    This module was designed to play with the new Curtis reissue chips by Alfa and contains two as3340, two as3310, two as3320 and an as3360 (oscillator, envelope, filter, vca).

    I've got a couple of through hole as3340 and an as3320 to experiment with as well in future projects :-) (I'm currently trying to get through-zero fm working with the as3340 using analog switches).

    What an awesome module - sounds amazing! Can go from very sweet and delicate to really nasty ! The two filters are great fun to modulate together and can make some very cool acid bass lines. I'm pretty impressed with it!

    20/06/20 As I liked it so much, I decided to build another one:

    No issues with the build.

    TINRS Edgecutter

    02/10/19 Built a TINRS Edgecutter and 08/10/19 built a second one.

    I changed the board to use thonkiconn jacks, a different LED switch and the e-switches used in MI modules. I have the parts to build another one, but only built one at a time in order to test the new layout!

    It was a pretty straight forward build and worked perfectly straight away. Useful module !

    The files can be found on my TINRS Panels.


    11/10/19 Built a Benjolin.

    I used a schematic posted on the electro-music forum and laid out a SMT pcb. The first try unfortunately revealed errors in the pcb when used on a bipolar psu. The voltage regulators can start regulating their rails at very slightly different times, depending on the speed of the psu rails coming up. This can lead to one regulator essentially having its output shorted to ground which stops that regulator starting. If this is the -ve rail then it can kill the v2164 chip. I added protection diodes so that the regulators would always start as well as a diode to protect the v2164. I also added a lot more filtering caps - eg decoupling caps on all the ics as well as filtering on the psu. It (by design) has quite a low output volume and, if I ever revise the pcb, I'll add an output gain cell.

    It sounds very clean and absolutely bat-sh*t crazy in the best possible way! Really useful as a cv modulation source as well as a crazy sound source - I suspect I'll build another one !

    22/12/19 Built a revised version

    This one has normalling of T1 to Osc2 cv input, T2 to Osc1 cv input and T2 to the filter cv input. I also added an opamp to boost the gain of the output to approximately 10v peak-to-peak (i.e. eurorack levels). However, I stupidly connected the power supply of the opamp incorrectly so jumpered it on this pcb. The version on the github is correct!

    I have very kindly had permission from the original designer of the Benjolin, Rob Hordijk, to post the design files on my github. Please note and respect that these are for non-commercial use only.

    The files can be found on my Benjolin github.

    Fates - DIY Monome Norns

    24/10/19 Built a DIY Norns

    Not really modular, but I'll use it to sequence the modular! This is really hard to describe! It's a raspberry pi with a wm8371 codec and a screen essentially. The magic happens in software - it runs lua as well as puredata on a linux kernel. There are loads of scripts on the monome site to download - some are sequencers, some sound processors and others are sound sources. It has a headphone jack, audio in and out as well as midi usb in and out.

    As well as Norns it can run Orac (hence the fourth encoder). Switching between them is very easy in software.

    It really is amazingly good fun!

    It was a trivially easy build. I 3d-printed a nice case.


    05/11/19 Built a Swirls (Lamb) module which is a smaller version of Mutable Instruments Tides.

    One of the trickiest builds - I was very kindly given the mostly built module by a friend. One of the opamps needed taking off and moving and the stm32 needed a number of pins reflowing. This was a really hard build due to the fact that unleaded solder and plumber's flux had been used. This meant that many of the pads were heavily corroded and needed scrubbing to expose bare copper. Also, reflowing the lead free solder was very tricky due to the corrosion. Fortunately it worked first time and sounds amazing with the Sheep wavetable firmware.

    MI Midipal

    24/11/19 Built a MI Midipal

    No issues with the build.

    8 Bit Pig GMO

    18/11/19 Built an 8-Bit Pig GMO I was given a pcb and panel for the 8-Bit Pig GMO - Thanks Jens ! I

    3320-based LPF

    26/11/19 Built an LPF

    Sounds great! There a couple of issues in the design - need to refine the resonance resistor, the tuning trimmer and set the correct bias - all trivial to do on this board but will be fully fixed when I next order some pcbs! The inspiration came from the TiNRS Rectangular Thing but I lifted ideas from many places, including the digisound 80, the as3320 datasheet and the cem3320 datasheet.

    30/12/19 Built another LPF, with corrected pcb.

    22/01/20 Built two more - this time I used jlcpcb for pcb assembly (!)

    The files can be found on my Analog Voice github.

    3340-based VCO

    3/12/19 Built a VCO Own-design 3340-based VCO (with ideas from multiple sources)

    Again, the inspiration came from the TiNRS Rectangular Thing with ideas from the datasheet and Digisound 80 added. It works really well and sounds amazing - I'm really happy with it.

    30/12/19 Built another one with revised pcb to correct errors.

    22/01/20 Built two more - this time I used jlcpcb for pcb assembly (!)

    The files can be found on my Analog Voice github.


    6/12/19 Built a Frankinkstides

    A friend sent me the board and panel mostly assembled (pcba). This is two Swirls (shrunken MI Tides + the max/min section of Kinks). It's a really cool module with a lot of complexity!

    Trivial build. No issues.


    15/01/20 Built a Typhoon.

    This is an adaptation of Clouds that uses a different MCU that has a larger flash size so it can accomodate alternative firmwares. It also has VCAs on the input and output.

    No issues with the build. Worked first time. Is great fun !!! To build the firmware, I needed to install an alternative version of the toolchain but there were no issues building the firmware.

    Headphone Amp

    15/01/20 Built a headphone amp. Own-design NJM4556-based headphone amp. This was based on the NWAVGUY standalone headphone amp. We had a local diy modular meetup and I wanted to demo some modules so designed this for the meet.

    It sounds really good. It has a 1 Ohm output impedance so can drive low impedance headphones with no problem. The NJM4556 opamps are used in parallel so it can also drive high-current demand headphones eg those with 600 ohm impedance.

    06/09/20 Built another one:

    14/10/20 Built yet another one:

    The files can be found on my Analog Voice github.

    Vactrol LPG

    19/01/20 Built an own-design LPG

    This is essentially a Buchla LPG with an analog switch to save the need to use a 3pdt switch which adds mechanical complexity and cost. Instead you can use a spdt on-off-on.

    Sounds great. No issues with the build.

    12/09/20 Built another one

    The files can be found on my Analog Voice github.

    3320-based HPF

    22/01/20 Built an own-design HPF

    Sounds great. No issues with the build.

    The files can be found on my Analog Voice github.

    x0x Heart

    02/03/20 Built an x0x heart along with pacemaker. (In truth this build took months as I kept doing a bit and then putting it off :-) )

    Not a particularly hard build - the SMT was pretty easy - but soldering the offboard connections and calibrating was not very enjoyable - not hard but just a bit tedious. For some reason I just didnt really enjoy this build - it felt more like a drag than an enjoyable experience. I'd definitely recommend the SMT pacemaker board as you can calibrate without having to use lots of jumper cables. There were no issues with the build and it works well.

    3310-based Dual ASR

    02/03/20 Built an own-design dual ASR based on the as3310 chip with normalled Gate 1 to Gate 2.

    Works well. I made a silly mistake in reading the datasheet and needed to hack in a couple of resistors, which is fixed in the next (final?) revision of the pcb.

    05/03/21 Built another one, from the corrected pcbs.

    No issues.

    The files can be found on my Analog Voice github.

    2164-based dual VCA

    19/03/20 Built an own-design dual VCA based on MI Veils.

    No issues with the build and it works well. You can chain an unlimited number together to form a large vc-mixer/vca.

    The files can be found on my Analog Voice github.

    06/02/21 Built three more:

    Monome Teletype

    08/04/20 Built a Monome Teletype

    Would have been an easy build except I got cocky and built it all in one go.... then found out the pcb had errors leading to a short from +5v to GND and it was a 4-layer board - the short was on internal layers so no easy way to fix it with jumpers. So I just desoldered everything (0402 passives) and moved it all to another board. The new board worked perfectly with no errors.

    I'd always fancied a Teletype but never tried one and wasn't willing to pay to buy one as I really wasn't sure if I would get on with it. So diying one made complete sense - and I really love it !

    Monome Grid Clone

    05/05/20 Built a Monome Grid clone

    Trivial build - this uses the adafruit trellis boards (eight of them) along with a Teensy 3.6 and a 3d-printed case to emulate a Monome Grid. The project is described on the Lines forum. It works so well, I've built a second one !

    4hp Wasp

    20/06/20 Own design.

    My prototypes had a stupid error - the resonance knob is backwards so I just swapped the pins on the pot. I have corrected the schematic and board on my github though! Sounds great - really really nasty but can clean up nicely. I much prefer it to my Doepfer one.

    To build them, the switch is a bit of a hack. As I couldn't find small 4-throw switches that were raised high enough off the pcbs I needed to extend the pins. I also used turn pin sockets to seat the chassis ends of the switch (I removed the plastic and soldered the switch to them for extra stability):

    21/09/20 Built another one from pcb assembled pcbs:

    16/10/20 Built three more from pcb assembled pcbs to have a polyphonic Wasp !:

    4hp ssi2144 LPF

    20/06/20 Own design.

    Sounds lovely - I absolutely love it!

    05/03/21 Built another one with the corrected pcbs.

    4hp ADSR

    20/06/20 Own design.

    Lovely ADSR - I made a stupid mistake though - the A,D and R pots are reversed. In my prototype I just swapped the pins on the pots. I'll correct the schematic and board files on my github though!

    21/09/20 Built another one from pcb assembled pcbs:

    Module Tester Module

    Own design (from MI module tester) I have the parts to build one.

    Worked perfectly first time. However, the footprints for some of the electrolytic caps were a bit small for convenience so I increased those as well as added some 0 ohm resistors for fine tuning the range of the trimmers for the precision voltage outputs.

    2164-based dual polarising VCA

    19/09/20 Built an own-design dual VCA based on MI Blinds.

    I really like MI Blinds but I usually only use two sections. As I wanted to use this in a small skiff I decided to build a 4hp version.

    This was quite a hard module to route - I ended up using 0402 sized passives. Because it is 4hp and there are a lot of ics and passives there are a consequently large number of control signals. Routing these traces in a 2-layer small board was entertaining!

    No issues with the build and it works well. You can chain an unlimited number together to form a large vc-mixer/vca.

    The files can be found on my Analog Voice github.

    Matrix Mixer

    20/09/20 Built an own-design matrix mixer.

    The switches allow selection of unipolar (attenuation) or bipolar (attenuversion) for each of the columns. Another switch allows normalisation to input 4 of either 5v or 10v (selectable via a jumper). It works really well and the knobs are very usable.

    I made a stupid mistake when designing it and cutting and pasting on the schematic (hence the fixes with the red kynar wire). All fixed on the latest version. Files are on my github.

    02/03/21 Built a revised version of my own-design matrix mixer. This is the revised board (all working - I removed the jumper to select 5v/10v as I only used the 5v. If I wanted 10v all I need to do is change the precision voltage reference.

    Ryk M185 Sequencer

    23/09/20 Built a Ryk M185 sequencer.

    I'd been watching this sequencer for ages (the Metropolis is based on it). It is really great fun and inspirational. The kit is *really* expensive though - I ummed and ahhed for ages, then a friend bought one and so I succumbed one evening after a few beers!

    The kit is really nicely put together and makes it a really trivial build unless you are a complete numpty and having a bad day (like I was). I made a few stupid errors - I blame it on building after stressful days at work (but really I was just being crap!) I soldered a diode too high off the board so thought I'd just take it out, clean the hole and replace it. I pulled off the top part of the pad! Oops. Easily fixed with a bit of kynar. Then, I read the pot values, checked three times where they should go, then soldered them in the wrong place so had to take a couple out and swap their positions. How tedious!

    I had some issues in calibrating it - the output scaling was easy to set but I had a 22mv offset in both channels. Ryk kindly provided a beta firmware which reduced the offset to 5mv offset in both channels (less than 1mv scaling error though). This makes it fine for v/oct on analog oscillators - not so great for digital without re-tuning or as a cv source for eg a vca, unless you use a precision added with offset.

    It's great fun and really inspirational to jam with...

    Oh, yeah - I remembered how much I hate through-hole!

    NLC Plague Of Daemons

    12/10/20 Built a NLC Plague Of Demons

    I was sent these in a pcb swap. Easy build. No issues. Brilliant fun and great sounds - love it!

    NLC Dual Timbre

    12/10/20 Built a NLC Dual Timbre

    I was sent these in a pcb swap. Easy build. No issues.

    Timo Rosendal SDSV+

    13/10/20 Built a Timo Rosendal SDSV+ drum voice

    Timo kindly sent me these pcbs. Easy build. Great online instructions. No issues. Really great fun - love it!

    Jakplugg Dust Of Time

    15/10/20 Built a Jakplugg Dust of Time

    Soldering was pretty easy (large 0805 passives) but I had issues with getting it to run. Initially the Teensy wouldn't boot - I was seeing a cyclic pattern on the reset pin. I took off the mic803 etc but it still persisted (but was working fine out of the module, powered by USB). It turned out there was an odd intermittent connection if the Teensy was pushed all the way down on the headers. Leaving it slightly proud on the headers by half a mm meant it would work fine.

    Monome Norns Shield

    16/10/20 Built a Monome Norns Shield

    Trivially easy build. No issues.

    I liked the Fates (Norns clone) and Grid clone that I built another Grid and also a Norns to go with it so that I can chain the two together to generate and process sounds.

    I 3d-printed a case....

    I may well build at least one more (I have a spare Raspberry Pi 3b - so would just need a display and dac).

    PreenFM2 and PreenFM3

    29/11/20 Built a PreenFM2 and PreenFM3

    Awesome sounds - the PreenFM3 is very new and firmware is alpha/beta so quite buggy but the UI is great!


    17/01/21 Building Tina

    Working on the code - got some basic code working....

    Analog TZFM VCO

    22/02/21 Built an own-design TZFM VCO.

    I'm really happy with this - the board worked straight away - I tested a lot of the ideas in LTSpice simulations and left a lot of jumpers on the board to try out different ideas. I also added a few extra resistor dividers to allow me to play with different values if I wasn't happy with the design. It works well and no need to revise it to get it to work. It tracks within a cent over 7 octaves (that I tested) and is very temperature stable. It's based on the ssi2130 analog vco chip.

    21/03/21 Built two more

    10/04/21 Built two more

    Analog TZFM VCO Expander

    27/03/21 Built an own-design TZFM VCO Expander. This adds cv-controlled mixing of the three main waveforms - it's great fun!

    ST Modular Good+Evil

    15/03/21 Built two ST Modular Good+Evil modules

    A friend (who sells modules commercially) had a number of these constructed in China but couldn't get it to work so asked me to help debug it (and keep the module). He also sent a pcb and panel to help debug it as no design files were available. It only took an hour or so to build and I had all the parts on hand. The issue turned out to be that he was using bipolar LEDs instead of unipolar. It looked really good, the issue is that, in the design, the LEDs are used as a unipolar diode so it didnt work correctly with two-lead bi-colour LEDs. Not sure how I will use them - seems like a fun but slighty odd module ! (I'm sure I will find a way !)

    Mutable Instruments Veils 2 (2020)

    22/03/21 built a Mutable Instruments Veils 2 (2020 version)

    Mutable Instruments Ripples 2 (2020)

    22/03/21 built a Mutable Instruments Ripples 2 (2020 version)

    Antumbra Knit

    05/04/21 built an Antumbra Knit (6hp MI Plaits clone).

    A friend gave me the boards along with a load of the parts - it seemed rude not to build it on a morning where there was sleety-hail. I had all the rest of the parts and it's such a trivially quick easy build... (the funny thing is that most of the parts I had spare were in 0402 and this is an 0603 conversion so quite a lot of the passives look tiny on the 0603 footprint :-) )

    Monome Arc Clone

    11/04/21 built a Monome Arc clone

    I 3d-printed a case for it. Straight forward build. For some reason it took me ages - I did all the soldering and then I didn't get around to putting it together for almost a year! It all worked with no isses.

    Instructions are on github: TheSlowGrowth's Monome Arc Clone.

    Module Tester

    I have an extra pcb and most of the needed parts. Mostly completed. This is a test-bed for some ideas I have.