A Collection Of My Favorite Eurorack
DIY Builds And Modifications
Remember... there's ALWAYS enough room for one more module in your rack! If not... buy another skiff  Smiley

A‑142‑4 Quad Decay  (Doepfer)

      Expander DIY

This low cost DIY adds eight toggle switches onto a separate 4HP panel which enables you to switch between self‑oscillating or trigger mode and/or time delay ranges of 2ms/2sec or 20ms/20sec. This add‑on increases the flexibility of this already versatile module

        EUROCRACK A‑142‑4 Quad Decay Expander DIY   (PDF)
Radio Music & Chord Organ  (Music Thing Modular)

      Review + *.WAV File Downloads

Radio Music is without a doubt one of the most creative modules in my setup. I have four of them now. The updated firmware allows the use of standard *.WAV files which makes it much easier to work with sample data

This module is an easy build because all of the components are through‑hole. It is EXTREMELY cost effective when sourcing your own parts from As a bonus, new firmware now enables you to turn the Radio Music module into a completely different module... the Chord Organ. Instead of playing samples from the MicroSD card, it synthesizes chords

If you are looking for some very weird and strange *.WAV files for your Radio Music module, there are more than 10GB of free samples w/cheatsheets available at these links:

         EUROCRACK Radio Music Weird Samples #1 (Fits on an 8GB MicroSD card)

         EUROCRACK Radio Music Weird Samples #2 (Fits on a 4GB MicroSD card)

         EUROCRACK Radio Music Weird Samples #3 (Fits on a 4GB MicroSD card)

         EUROCRACK Radio Music Weird Samples #4 (Fits on a 1GB MicroSD card)

(You can preview the samples here at SoundCloud)

Update October 2019:
With some power skiffs, Radio Music and Chord Organ modules will only power on about 50% of the time. After searching some forums, I discovered a workaround which is to remove the microSD card before turning the power on and then plugging the microSD card back in for normal operation

The Full Parts Kit or the PCB/Panel Kit from are the best values I've found anywhere. The PCB/Panel set also includes the required MicroSD card adapter for free
Discrete SV‑VCF  (Manhattan Analog)

      Panel/PCB Build Notes & Review

This module is similar to Oberheim's SEM filter and the mixer is inspired by Moog's CP3 module... also built with transistors which gives it a distinct sound. Although this is a labor intensive build, the end results are worth all of your efforts. My best advice for this build is to take a little time and do some research before you start building. If you focus too much on some of the earlier posts for the build discussions at, you will be thoroughly confused because they deal with several different PCB versions. I definitely got lost because of "too many" suggestions. I found only a few posts which were actually relevant for my build (v1.4/Main Board + v1.3/Jack Board)
  • I used Tayda Electronics 16mm pots with solder lugs as suggested by one Muff Wiggler. Big huge mistake. I was trying to save $$$ by using what I had in my parts kit. The amount of extra time I spent soldering these using solid wire was a giant hassle. Be sure to use right angle PCB mount pots which look like this (they are the same price as pots with solder lugs and will save you an enormous amount of assembly time so... it's a no‑brainer)
  • As suggested by the designer, I opted to use a 1K Tempco resistor at PCB silkscreen location R44*. This special resistor is available from Modular Addict. From what I've read about this, after being powered up for 2+ hours in the case, components tend to heat up and this Tempco is there to prevent temperature drift for that part of the circuit

  • I was unable to find a BOM or build docs at the Manhattan Analog website but I did find a good BOM at this link for reference There is also a Mouser Cart BOM at the Muff Wiggler link above but use that one with caution! Some of the transistors and other parts listed there are quite expensive. The BOM total $$$ was much higher than the parts I was able to source from Modular Addict and Tayda Electronics. With the exception of the Styrene Caps (P/N: 23PS210), Ferrite Beads (P/N: BL01RN1A1F1J) and the LM377 (P/N: LM337LZ/NOPB), I was able to source all components from Modular Addict and Tayda Electronics

  • There are 13 SMD components. Two on the Main Board and eleven on the Jack Board. For the PCB versions listed above, the components are placed as follows:
    • Jack Board (Back)
      • (2) 0.1uf Caps @ Pad Locations Marked ".1"
      • (2) 22pF Caps @ Pad Locations Marked "C"
      • (2) 330R Resistor @ Pad Locations Marked "3"
      • (4) 47K Resistor @ Pad Locations Marked "4"
      • (1) TL072CDR IC @ Pad Location Marked "072"

    • Main Board (Back)
      • (2) 0.1uf Caps

    Note that if you use a 1K resistor on the front of this board at PCB silkscreen location R44*, there will be two pairs of SMT pads which are not used and left unpopulated. One pair of pads is used for a 1K SMD mounted resistor (I used a Tempco through hole resistor on the front instead) and the the other pair of pads have large holes in them and are used only as test points. Compared to these test pads, the pads I populated with the 0.1uf capacitors have very, very small holes drilled in them. Much smaller than the test pads. I don't like working with SMD stuff but found all of these components were very easy to solder by hand using a fine tip iron

  • Some of the BOM's floating around are showing expensive bipolar transistors. The designer pretty much says not to bother using expensive transistors. Standard 2N3904 and 2N3906 transistors will work just fine. Quote from the designer - "I couldn't justify $6 for 4 transistors - x4 per board - when 2N390x at 2¢ each work and sound just as nice. As far as matching goes, I've built them with matched and unmatched transistors and couldn't really tell any difference. I recommend loosely matching them as a matter of best practice but it's not something you should worry about."

  • I socketed the resistor at PCB silkscreen location R13* on the Main Board. The designer mentions this value can be experimented with to fine tune the mixer/filter sections. I am currently using a 330K resistor here (the default value is 390K) and it sounds great. As another builder mentioned, this 330K value slightly tames the resonance. I will experiment with other values later on. Suggested values to tinker with here are between 270K and 470K
For calibration, you will definitely need to check out the info at this thread posted by user "negativspace" (Manhattan Analog Designer)
         Search for the phrase "Holy crap, this isn't hard"  Smiley

I'm really digging this module. I built two and am happy to report these make a good substitution for the Oberheim synth sound I've always craved but never owned. Here are some links with a good collection of demos:

This video demonstrates a very cool effect similar to a track titled "905" on The Who's LP "Who Are You?". That track was played on one of the first multiphonic Polymoog synths way back in 1978. Another synth I've heard which comes close to this great effect is the Roland Super JX‑10/MKS‑70 - Patch G‑3: ROBODROID DELUXE 39 47

A very detailed overview and demo by DivKid

A collection of audio demo clips. Check out "Bendy Bandpass"... oh yeah!

The PCB/Panel set is usually out of stock everywhere but you can still buy a PCB/Panel set (or a fully assembled module) direct from the designer at
Chaotica v1.1  (Elby Designs)

      Panel/PCB Build Notes & Review

Of all the modules I own, Chaotica instantly moved to the #3 spot on my "Top 10 List" after building and hearing it. A phenomenal CV generator for complete mayhem!

The one major drawback you need to be aware of is that if you purchase an older version v1.1, it will not fit in a majority of enclosed skiffs. The PCB is incredibly deep at a whopping 101mm (4 inches). The newer v2.0 models have been redesigned at only 60mm deep and will and fit in most enclosed skiffs. To accommodate the depth, I had to build my own open‑back case. Other than this major flaw on the older versions, this one is a Highly Recommended Build!
  • My kit had eight PCB's to assemble. Yes... that's not a misprint. EIGHT. There is one large square main PCB. Mine was labeled as ED120 v1.1. Three of the rectangular PCB's are used for a majority of the pots and jacks. The other four PCB's are very small and are used to attach the Y, Z and RESET/INHIBIT Jacks and also the EYES Switch. I was a little confused about the four small PCB's because three were blue and labeled "Carrier" and one was green and labeled "Carrier V1.2". I sent an eMail to Elby Designs and was told that the solitary green one labeled "Carrier V1.2" is used for the EYES Switch. The A5K Pot is installed on the Main PCB at silkscreen location P101 (Labeled ML DRIVE on the front panel)

    This is how I populated my PCB's with components
    • Board Revision(PCB Type): Components(Silkscreen Location)
    • ED120 v1.1(Main PCB): A5K Pot(P101), X Jack(J103) and TAME/WILD Switch(S101)
    • Carrier(Small Blue PCB): Y(J102), Z(J101) and RESET/INHIBIT(J204) Jack
    • Carrier V1.2(Small Green PCB): EYES Switch(S102)
    • Panther - Jack-Switch Board Rev 3.1(Rectangular PCB): Blue Jacks - CV RATE(J1), CV DAMPING(J2), CV OFFSET(J3) & CV GAIN(J4)
    • Panther - Pot-Carrier Board Rev 1.4(Rectangular PCB): A100K Log Pots - RATE(P1), DAMPING(P2), OFFSET(P3) & GAIN(P4)
    • Panther - Pot-Carrier Board Rev 1.5(Rectangular PCB): B100K Linear Pots (P1, P2, P3 & P4 - Attenuators labeled w/Right Arrow⟶)

  • Connections for the 16‑pin ribbon cables
    • J201 on Main PCB   ➟ ➟  J6 on Pot-Carrier Board Rev 1.4 (Note: Don't confuse this with J6 on Pot-Carrier Board Rev 1.5)
    • J202 on Main PCB   ➟ ➟  J6 on Pot-Carrier Board Rev 1.5 (Note: Don't confuse this with J6 on Pot-Carrier Board Rev 1.4)
    • J203 on Main PCB   ➟ ➟  J5 on Jack-Switch Board Rev 3.1
    • J301 on Main PCB   ➟ ➟  Case Power

  • If you have PCB revisions different from the ones I've presented here, I recommend that you eMail Elby Designs to get additional info for correct component placement. Elby Designs was friendly and also very fast to respond with technical help

  • One of the best descriptions about this module and how is works is at Ian Fritz's website, the Chaotica designer. There are many audio clips here and also an in‑depth video

This module is somewhat difficult to purchase online. Elby Designs almost always has the full kit in stock but it's extremely expensive to ship from Australia to other countries these days. Modular Addict used to keep this one in stock on a regular basis but I've not seen it around since early 2019
CGS10 Keyboard & Transposer (Tear Apart Tapes)

      Panel/PCB Build Notes & Review

I find this to be a very useful module for my music style (Tangerine Dream, Vangelis, Ambient, etc...). Using the CV Out Jack and pressing buttons on the front panel during active sequences will transpose the riff up or down in a 16‑semitone range (one octave plus four‑semitones). This module also doubles as a keyboard which enables the operator to play one note at a time... great for sending triggers or percussive notes on the fly

This is a very easy build with a low cost, low parts count. It has a combination of through‑hole and SMD parts, all of which are easy to solder in place because everything is spread out on the PCB. The only part I had trouble finding was the specialty Matrix Keyboard Scanner IC made by Fairchild - P/N: MM74C922. This IC is available at Jameco Electronics but it is pricey at $11. This specialty IC is also available at Amazon and eBay in quantity at a lower cost. This IC is no longer made by Fairchild which is why it's so expensive these days. There are 16 Tact Switches required. I used 6mm x 6mm x 13mm tact switches available from Tayda Electronics (SKU: A‑5156). I also purchased the Jacks (SKU: A‑2563) and Potentiometer (SKU: A‑1851) from Tayda Electronics. I was able to source the remaining components from When you buy the PCB/Panel, a Xerox page is included with a Build Guide and BOM. Calibration was a breeze with the supplied instructions
  • I'm always curious about unused pads on DIY builds. I contacted the designer of this one and he explained the following about the unused pads as detailed in this image
    • The two unmarked pads on the front are for a bypass capacitor (100 nF) which isn't really necessary
    • The two pads with holes marked CV and Gate are for possible use if one wants to build the keyboard into some other device, say a real keyboard or some other keypad thing, like an old telephone pad or something else

I've put together a Mouser Cart BOM and also a detailed BOM in PDF format for downloading here*

      Mouser Cart                  BOM (PDF)

* SPECIAL NOTE: The Mouser Cart does not contain all required parts for this build. Refer to the BOM PDF for Jack, Tact Switch, IC & Potentiometer part numbers available from Tayda Electronics. The BOM PDF has a link to the eBay store where I purchased the 74C922 Matrix Keyboard Scanner IC. As always, when purchasing parts from Mouser, increase the quantities of resistors and capacitors to 10 or 100 for substantial savings

Some of the pitfalls you will need to watch out for when building this one are:
  • Make sure you install all of the tall components on the back of the PCB
    • These components are the two Trimmers, the Power Header and the electrolytic capacitors if you use part numbers other than ones shown on the BOM (i.e. taller than 9mm. Silkscreen outlines on the front of the PCB are misleading. If you install these tall components on the front, you won't be able to fit the front panel in place. You might be able to bend taller electrolytic capacitors downward at a 90 degree angle to make them fit but the two trimmers and power header will absolutely need to be installed on the back. For my build, I used two of these capacitors (Nichicon P/N: UST1H100MDD1TP) and one of these (Nichicon P/N: UST1H2R2MDD)

  • The standoffs and nuts I used to connect the front panel to the PCB were made of nylon. This is recommended in order to prevent any short‑circuits on the PCB close to where some of the tact switch pins are located. If you decide to use metal standoffs and metal nuts instead, use some plastic washers to raise the standoffs up & away from the PCB

  • There is a Xerox page included with each PCB/Panel kit. There are some misprints with the BOM quantities
    • Only four 200K resistors are shown but you will actually need five 200K resistors
    • Only nine 100K resistors are shown but you will actually need ten 100K resistors
The original design is by Ken Stone of Cat Girl Synth fame. You can find a detailed explanation with schematics of his original design at the Elby Designs website

As of July 2020, Modular Addict still had some of these PCB/Panel kits in stock
ChaQuO v2.0  (Elby Designs)

      Panel/PCB Build Notes & Review

This chaos generator is similar to Chaotica. I like Chaotica better than ChaQuO because there are more CV inputs which can make things extremely wild at times. ChaQuO is slightly different because it has a separate Quadrature Oscillator with extra outputs for Sin+ / Sin- / Cos+ / Cos- and these four signals can be used to supply a drive signal for the chaos generator section. The designer, Ian Fritz, sums up differences between the Chaotica and ChaQuO modules;
  • "Chaos requires three degrees of freedom, or variables. Chaotica has three VC opamp integrators that correspond to the three degrees of freedom, so it can oscillate on its own. ChaQuO is a second order system, and an external driving source is required to provide the third degree of freedom. The double-well chaos (EZ Chaos) board was the first board I designed, and it was intended to be the simplest way for folks to get into a DIY chaos generator. ChaQuO with its built-in driving source was its follow-on."
There is a YouTube demo showing the ChaQuO in action along with a good explanation of chaos modulation here

Thankfully, the new ChaQuO V2.0 PCB does not have the same issue as the V1.x Chaotica design... an extremely deep PCB. This one fits nicely into most cases and is only 55mm deep (compared to Chaotica which is 101mm). The clever design now being used on Elby V2.0 builds was somewhat tricky for me to figure out at first. Once I looked at all the documentation and the 3D PDF files, it started to make sense. There were no images of a completed module in the Build Guides anywhere so I've put together some notes and images which might make this build a little easier to complete
  • There is a jumper wire which needs to be soldered onto the Main PCB which runs from the Column 2 PCB 16-pin header over to the Column 3 PCB 20-pin header. The easiest way is to run this across the top of the PCB (Figure A and B)

  • Take care when plugging the Main PCB into the four rectangular PCB's. The 16-pin and 20-pin headers need to be aligned in the center. It's quite easy to accidentally shift these pin headers left or right and plug the Main PCB board off‑center. The male headers have notches but the female headers do not. Luckily, I discovered my mistake before I turned on the power (Figure C)

  • There are ten PCB's in this kit! Not a misprint. TEN! Lining up the four rectangular PCB's in the correct order is crucial. Refer to the image for the correct order (Figure D)
As of June 2020, Modular Addict still had some of these full kits in stock

Figure A
(Click For Larger Image)
Figure B
(Click For Larger Image)
Figure C
(Click For Larger Image)
Figure D
(Click For Larger Image)
Waveslicer  (Horstronic)

      Panel/PCB Build Notes & Review

I was absolutely blown away by all of the amazing sounds I'm getting out of this module!

Three IN's, four CV IN's, three OUT's and eleven knobs enable a large array of different "Waveslicing" audio options

A Highly Recommended Build for many reasons:
  • The designer really put some thought into the design of this PCB layout. He had the DIY people in mind. There are solder pads on my v2.3 PCB which are double duty... resistors can be either SMD or mounted through hole. I wish more designers would offer this as an option

  • Likewise, the 3.5mm jack holes are quite versatile because they will accept either PJ301BM or PJ398SM jacks. Very cool when searching your inventory for available parts!

  • The overall DIY cost was very low because of all the easy to find parts. With the exception of two dual‑color LEDs and one LM4040, I was able to find everything at Tayda Electronics. I hate builds which use SMD but this one was quite easy because none of the IC's are SMD. They're all through‑hole. There are 24 SMD components (all capacitors)... but don't let that prevent you from getting this PCB/Panel. It was an easy build and it sounds great

The PCB/Panel set is out of stock just about everywhere. Fully built modules show up on eBay from time to time for ~$150 (USD)
Suiseki Phase Shifter  (Old Crow Modular)

      [ Mid-1970's "Small Stone" Phase Shifter ]

      Panel/PCB Build Notes & Review

The sounds this Phase Shifter effect can produce are very rich and lush. Tangerine Dream and Pink Floyd are hovering nearby when this one is active. Immediately after building this one and hearing it, I ordered a 2nd one to use for stereo effects and/or additional CV's

All components were inexpensive and simple to source (total was under $24). This build was very easy. There was only one oddball resistor value I did not have in my parts kit (30K) which I sourced from Tayda Electronics. This is an inexpensive and feature packed effects module in a small 4HP space. At this low price you should grab a pair
  • I recommend mounting the 10K trimpot (R27) onto the component side of the PCB. I have no idea why the silkscreen for this component is printed on the back or why it's even mentioned as an option in the Build Docs. If you mount it on the back, it seems impossible to install or remove the module from the case!?!? Calibration is a breeze. While turning the trimmer, just listen to how "full" you want it to sound

  • I modified some standard 9mm Alpha pots by carefully bending the three pins straight which effectively turns them into right angle mounted pots

  • I opted to use standard 3.5mm jacks and not the ones on the BOM. With a little manipulation and some hookup wire, the Tip and Ring connectors can be wired onto the PCB. The ground pin is then soldered directly onto the PCB for stability

  • As noted in the Build Docs, it is also possible to change this module over to have a "Uni‑Vibe" effect. If you plan to do this, you might want to socket the capacitors at C13, C14, C23 and C24. A toggle switch or some jumpers would have been a nice addition but unfortunately... there's no room

  • The 3mm RedOrange/Green Dual‑Color LED I used was a Lite‑On brand P/N: LTL‑10CHJ

  • Except for the Dual‑Color LED, I found all of the parts at and Using the standard 3.5mm jacks and Alpha pots I already had in my parts kit saved me some extra $$$

    Audio examples available at the Old Crow Website

    The PCB/Panel set is usually available for purchase at
4046 Shaper  (Barton)

      Panel/PCB Build Notes & Review

I was able to easily source all the components from Tayda Electronics at a minimal cost of only $8 for everything. The PCB is extremely well made and easy to solder. The build guide is easy to follow and there are no surprises. As usual, the panel made by Oscillosaurus looks fantastic

The things I would have changed with my build is to add sockets for the 1uF and 10uF electrolytic caps (Slew Control) and also for the 10K resistor. The build guide mentions that you can substitute different values at the 10K resistor location and I think it would also be interesting to alter the two electrolytic caps for experimentation

I wish I had discovered the Barton DIY PCB's and Panels a long time ago. Barton DIY modules are some incredible value priced gadgets and the 4046 Waveshaper is no exception. The demo video made by Barton is OK but... I encourage you to watch this one made by MidiverseTV instead. It gets into some better sound details and shows the output on an oscilloscope


The PCB/Panel set is available for purchase at
Pure Noise  (GMSN!)

      Panel/PCB Build Notes & Review

This one is a great value‑priced, multi‑NOISE module with less than 45 components

The four different noise sources (Blue, White, Pink & Brown) are quite interesting when used with a Sample & Hold module. They each produce unique random glitches. For years, I've been using the PGH Toolbox module to generate noise. It's nice to have these four different noise sources for a wider variety of randomness. Some of these noise sources are MUCH brighter than the solitary PGH Toolbox noise source
  • Except for the DMMT3904W 6-pin Matched Bipolar Transistor in a !!!Microscopic!!! SOT-363 package, all of the SMT parts were very easy to solder in place. As stated by the module designer in one of his calibration videos, not all DMMT3904W IC's will work because the modern day tolerances of these IC's are "too precise". In a batch of ten, maybe eight will work correctly with this design. After building, you may need to remove the DMMT3904W and try another one if no noise is generated. My first build did not work. Lucky me! After replacing the DMMT3904W with another one from the same batch, it worked perfectly. I'm glad I watched the designer's calibration video first. So... moral of the story... buy two or three DMMT3904W IC's in case you need to replace one. They're inexpensive

  • There is a helpful trimmer calibration video on YouTube here
The PCB/Panel set is available for purchase at
Rampage  (Befaco)

      Panel/PCB Build Notes & Review

With more than 800+ solder connections and 300+ components, the Rampage PCB/Panel is a VERY labor intensive build. However, the payoff is totally worth the effort. The number of new features this single module can add to your rack is staggering... Burst Generator, Polyrythmic Gate Generator, Ping‑Pong LFO, Dual Low Pass Filter, Voltage Controlled Trigger Delay, Peak Voltage Follower and Dual Slope Detector... just to name a few

I've built more than 25+ different PCB/Panel kits but the Rampage is my first BEFACO project. I was really impressed with the quality double sided PCB's and the accurate/easy to follow assembly guide and BOM. Everything worked the first time when I powered‑up and I'm looking forward to building more BEFACO modules

If you plan to source components yourself such as mini‑toggle switches, resistors, pots and LED's... be aware of the following for PCB v1.3.2 (and other PCB versions)
  • Standard mini‑toggle switches from Tayda Electronics and eBay will NOT work because the through‑hole lugs are too wide for the PCB. Use the exact part number as shown in the BOM

  • Likewise, standard pots from Tayda Electronics will not work because BEFACO pots have a unique footprint and some are the dual‑gang variety with six "through‑hole" solder pins. These special pots are available at the PARTS webpage

  • Resistor spaces on the PCB's are designed for use with smaller 1/8W resistors having a body length of 3.25mm. I always use 1/4W resistors for my builds because I currently have a bazillion of these in my parts inventory. I populated the entire board with the larger 1/4W variety instead which have a body length of 6mm. They worked but I had to insert each one at a 45 degree angle which led to spacing problems while trying to sandwich the two PCB's together. Using longer header socket pins solved this issue

  • If you plan on using IC sockets, be aware that there is virtually no clearance between the two circuit boards. I had to use some longer than normal header socket pins when joining the two PCB's together. If you plan to solder the IC's directly onto the PCB instead, this is a non‑issue

  • Because of the low clearance between PCB's, you may need to mount the two electrolytic caps horizontally if they are not the "low profile" variety

  • The BOM calls for 2mm LED's. I only keep 3mm LED's in my inventory. Although these are too big to fit completely into the front panel holes, they still worked when recessed. However, there is a slight bleed‑through to adjacent LED's when they are lit. I opted not to purchase the 2mm variety LED's because they are priced 10x higher than more commonly found 3mm LED's. If you are picky about LED bleed‑through, you may want to source expensive 2mm LED's instead

    Currently out of stock but the PCB/Panel Set and the Full Kit are sometimes available at

      Panel/PCB Build Notes & Review

I'm crazy about this PØwr utility module from I think every Eurorack DIY'er needs one of these. This is very convenient when testing and calibrating new builds. Sure... you could have a ribbon cable sticking out the side of your rack instead but this module looks classy *PLUS* safety‑wise, the mini‑toggle switch keeps the 16‑pin header connector powered off when you're not using it

This is a super easy build, a low‑cost PCB/Panel and requires less than $2 in parts!!! The oddball connector sandwiched in the middle was supplied with my panel. As mentioned in the build thread at Muff Wiggler, some inexpensive mini‑toggle switches with solder lugs are too big. For my inexpensive mini‑toggle switch, I had to use a Dremel tool and carefully file down the solder lugs and some red plastic before the oddball connector would mate flush with both panels. I would recommend buying the correct sized mini‑toggle switch with PCB pins to avoid the hassle. This module has been working overtime in my rack lately. Incredibly useful!!!

As of June 2020, The PCB/Panel set is available for purchase at
Burst  (Befaco)

      Kit Build Notes & Review

Another Unique And Feature Packed Module From Befaco!

(+Fast ▻▻▻ Slow Down) / (+Slow ▻▻▻ Speed Up) / 64 Triggers / Probability Knob... oh yeaaah! This one is a definite winner!!! I was really looking forward to getting this one built and in the rack. It produces some incredible patterns unlike any other modules I own. There are a couple of IN's and OUT's for a wide variety of control to sync other modules and/or receive CV's for mode changes

  • All my other Befaco builds used the PCB/Panel while sourcing my own parts. This is the first Befaco "Full Kit" I've assembled and I was quite happy to use the smaller 1/8W resistors. In the past I've used 1/4W resistors and the lack of space was nearly unmanageable. Like all the other Befaco PCB's, everything is crowded so pay close attention to the resistor silkscreen locations

  • When attaching the two PCB's, ensure that one of the flat sides of the brass standoff is parallel and flush with the edge of the nearby IC socket. Otherwise the PCB's won't align properly

  • If I don't recognize the brand‑name of caps in a "Full Kit", I always replace them with high quality caps from a manufacturer like Nichicon, TDK, Panasonic or WIMA. Luckily there were only fifteen caps for this build. The ones in the kit were Huang(?) so they went straight into the trashcan. If you decide to use different brand caps, be aware that the electrolytics used here are low profile so they can fit between the layered PCB's. If using taller caps, you will need to shield and bend the leads at a right angle

  • Assembly time was quick and easy with no surprises. Compared to a Crush Delay or other "non‑Rampage" Befaco build, this one has a low parts count. Calibration was a breeze. Just hold down some buttons during power‑up
DivKid has a great overview at this link

Currently out of stock but this PCB/Panel set is sometimes available for purchase at
Jupiter Storm  (HexInverter)

      Panel/PCB Build Notes & Review

This module can really crank out some crazy noise and random outer‑space sound effects

This is one of the more interesting noise generators I own and it's definitely a keeper. There are some extremely unique sound effects you can achieve once you start toying with the outputs on the I, IV, VIII and XI Noise Channels. The IC's and other components were inexpensive and easy to source. All IC's are priced less than 50¢ each. Note that for best results, the designer recommends using only Texas Instruments brand IC's for IC2, IC4, IC6, IC7 and IC8. Also, be aware that no additional parts are included for mounting the PCB onto the panel. You're on your own

The through hole build and off‑board wiring was very easy except for a few annoying hurdles with my Version 1.1 PCB:
  • Mounting the crazy oversized PCB onto the panel is an all‑afternoon event. If mounted to the panel at a right angle, the depth measures 90mm (about 3 1/2 inches) and it's impossible to fit into some Eurorack cases which are enclosed (ones with a backplate like the PGH Case[90]). I ended up following some suggestions at a Muff Wiggler thread and used some sheet metal bent at right angles to mount it parallel to the panel. However, this still presents a major issue because it overlaps each side of the panel by 11mm (about 1/2 inch). The PCB is much wider than the panel. I'm only able to install it into my case as long as there is a blank space on either side of it or if it is installed next to a module which has a lot of clearance on one side (however, no modules like that exist in my rack)

  • Standard sized SPDT mini toggle switches will not fit into the panel holes. I had to drill the panel holes slightly larger before a Tayda SKU: A‑4567 would fit

    Despite the many hassles needed to mount the PCB onto the panel and then make it fit into a standard Eurorack case, I highly recommend this DIY module. During the mounting and installation phase you will absolutely be cursing it the entire time but hey... I think all modules receive threats and curses during a build. This one will get a double dose of four‑letters thrown at it

    The PCB/Panel set is available for purchase at
4013 Dual Flip‑Flop  (Omiindustriies)

      Panel/PCB Build Notes & Review

I had one professor during my Electrical Engineering studies who spent three weeks of a Digital Microcircuits course explaining the logic of JK Flip‑Flops. After three weeks, the only person in the class who really understood how it worked was the professor! I feel like I'm back in school trying to wrap my head around this one. It's an excellent module for creating random, glitchy behavior. Using it with my Noise Reap VFD+ produces some amazing psychedelic cacophony and SciFi turbulence I've never heard before. This one is a definite keeper!

  • I really like the PCB the designer used for this one!!! The solder pads are very large and because of that, it was the easiest SMT module I've built to date. Like all PCB's with four‑point‑cross GROUND pads, you will want to turn up the soldering iron to a higher setting when soldering any GROUND pads

  • The holes in the panel for 3mm LED's are better suited for 2mm LED's. If you use 3mm LED's, they will be recessed. Not really a major issue unless you like to have your LED's stick out the front panel. I used Tayda Electronics 3mm super bright LED's and replaced all twelve 4.7K resistors with 10K resistors (Blue/White/UV/Red/Green/Orange). The six different colors make a mesmerizing lightshow when it's a poppin'

  • The PCB silkscreen shows values and IC part#'s for easy placement of all components except R1. I had to pause in the middle of soldering and find a schematic to determine that R1 = 47 Ohms

  • The part count is small (less than 60 SMT) and all components are priced low, low, low. The most expensive component was the TL074IDR IC at 82¢ each... only three are needed

    The PCB/Panel set is available for purchase at
Eurobuffer  (Barton)

      Panel/PCB Build Notes & Review

This is a very useful 4‑Channel 1‑to‑3 Buffer. It also allows you to take a single input and replicate its output to 12 individual jacks. Since this is an "Active" buffer, it has the advantage over a "Passive" buffer because there is no signal degradation. The circuit uses a TL074 Op‑Amp wired as a unity buffer

There are only 36 components to solder in place which makes this a quick, easy and very inexpensive build

Currently out of stock at most places but the PCB is always available from Barton Musical. The super‑cool noir repanel made by Oscillosaurus is usually in stock at
ZeroScope  (VPME.DE)

      Panel/PCB Build Notes & Review

I had this mini‑oscilloscope in my rack for more than a year. It never worked 100% after building it because there was a flat line for all readings less than 100ms. There was also a "T?" error showing at the bottom left of the screen. As suggested by some members at the Forum, I resoldered R2, R4, D2 and checked for short circuits around the OpAmp. No results

I finally got it working after cleaning the entire board with IPA to remove extremely small amounts of flux in‑between all components which are packed closely together (which is pretty much the entire board). I don't use extra flux for my builds but the flux core in the solder leaves very small traces and was apparently causing random short circuits. I had no idea. This certainly changes the way I will build my modules from now on

Even though this build uses 80% SMD components, I was able to solder everything by hand using a fine tip iron and had no issues (other than the flux problem)

Currently out of stock most places but this PCB/Panel set is sometimes available for purchase at
Quad Trapezoidal LFO  (Barton)

      Panel/PCB Build Notes & Review

The Barton QTLFO is a very interesting module the way it feeds itself different envelope timing sequences. It's not what one would typically call a "random" setting but it certainly adds unpredictable patterns into the beat. It outputs four trapezoidal waveforms which are synchronized with each other. One envelope begins to rise when the previous envelope falls and reaches zero. After the fourth envelope reaches zero, the entire sequence cycles again and again. Each output has a separate knob to control the envelope rise and fall time

This one is a low‑cost, low‑count component build. The components used are very common and excluding the PCB/Panel, the cost was less than $12 (USD). The most expensive components are the four anti‑log potentiometers at 50¢ each! The build time took only a few hours and it's very simple

The PCB/Panel set is available for purchase at
÷N COM  (Random*Source)

      Panel/PCB Review

I won't dwell on the Random*Source line of DIY modules for very long. My advice is to buy ALL of them because each one is high quality, feature packed and an easy build. This line is slightly more expensive than other DIY modules because a majority of their newer builds have all of the SMT/SMD components pre‑soldered on the PCB's. My favorite is the ÷N COM

PCB/Panel sets are available for purchase at

Honeyeater  (ST Modular)

      Panel/PCB Build Notes & Review

Rich sounds are made possible by using the FM and Sub‑Octave switches which really take advantage of the Curtis Oscillator. There are also plenty of CV inputs to mangle the sounds (FM, PWM, V/OCT). The Noise toggle switch adds a very nice option to give you that 1970's Synth/Mallet/Percussive combo feel (i.e. "Autobahn" by Kraftwork). I like to set the jumper on the back to "Hard Sync" and feed a complex audio signal into the SYNC input. This can create some interesting "Moog" style sounds. As the main ST‑Modular webpage states, you can get some "very rich sounding analog synth sounds" from this module

This one is a 90% SMD/SMT build. The only through‑hole components on the PCB are the pots, jacks, trimmers, polystyrene capacitor and the custom CEM3340 Curtis VCO IC. Original CEM3340 IC's are difficult to find these days. When you do find them, they can be pricey. A company called Cool Audio makes the equivalent AS3340‑DIL 16‑pin DIP IC for only $6 (USD). I used this Cool Audio IC and the sound is phenomenal! This build was slightly challenging for me because I'm lousy at working with those miniature 0603 sized SMD/SMT components. I prefer 0805 sized components instead so it did take longer than my usual builds

Special Assembly Notes:

1) Polystyrene Capacitor - The 1.5nF polystyrene capacitor I used was a Xicon P/N: 23PS215. When soldering this component in place, I recommend using a slightly lower temperature than you normally would. This component is extremely sensitive to heat damage. The soldering temperature should remain below 260º Celsius (500º Fahrenheit) with a touch time limited to a maximum of only three seconds per leg. I always use a heat sink when soldering polystyrene capacitors, thermal fuses and other heat sensitive components. If you don't have one, it's a recommended and inexpensive item to keep in your toolkit. You can find them at Jameco and eBay

2) Calibration - Use a MIDI to CV converter and a tuner, set the Tune and/or Fine pot to reach C, play C1 and C2 alternately and check if it stays on C. Adjust the v/Oct trim pot on the front if it's off a bit. Repeat that for C2 and C3 and so on. Adjust high freq trim if you can't get higher octaves right. Adjust v/octoffset to reach the correct note. You may also use an oscilloscope or a multimeter in audio frequency mode and using a quantizer in octave mode to adjust frequencies of 100hz, 200hz etc. There are some YouTube videos about the calibration of DIY oscillators. Its always the same basically. Keep in mind to calibrate only after heating the oscillator up for about 20 minutes

Sources are few for this one but PCB/Panel sets are currently available for purchase at Pusherman

Analog Drum  (Barton)

      Panel/PCB Build Notes & Review
Figure 1
(Click For Larger Image)

This one has a myriad of sounds and is one of my favorite "go‑to" modules for percussion. It is a very easy through‑hole build

The build docs do not say much about one of the cool ways to wire it correctly and there are no diagrams showing how. The CV jack can be normalized to the OUT jack for some extra sounds & effects. The TIP lug on the OUT jack connects to OUT on the PCB and also to the SWITCH lug on the CV jack. This effectively turns the CV attenuator knob into a self‑frequency modulation control and adds interesting sounds & effects when no cable is plugged into the CV jack. The image in the build docs for the wiring is somewhat misleading. The OUT jack is actually shown in the wrong position on the panel as compared to all the panels, builds and demos I've seen on YouTube. The OUT jack always appears on the panel in the middle position but it is shown in the build docs on the bottom so be careful when you are wiring this one

The image in Figure 1 shows proper wiring for how the CV jack is normalized to the OUT jack to achieve the extra sounds & effects  

MidiverseTV has a video demo at this link
             Note: It skips 3 minutes of the build process

The PCB/Panel set is always available from Barton Musical and it shows up in‑stock from time to time at
4R  (Transient Modules)

      Panel/PCB Build Notes & Review

One of my favorite CV generators. An extremely compact quad random voltage generator in only 2HP. It generates two different random stepped voltages per input each time a rising edge is sensed at TRIG1 or TRIG2. The inputs are independent so they can work at different clock speeds. TRIG2 is normalized to TRIG1 making it possible to get four random values with just one trigger. The voltage range of each pair of outputs can be set as unipolar (0V to +5V) or bipolar (-5V to +5V) by using jumper blocks on back of the PCB. You can set these jumpers so that two outputs are unipolar and two outputs are bipolar or make all four outputs the same. I have all the jumpers on mine set to bipolar so it will output the widest range of CV signals

There are only four SMD components you need to solder and the rest are all through hole (there are another twelve SMD components with small footprints but these are pre‑soldered in place at the factory). This one is a very easy build. All components are inexpensive and easy to source. The exception would be the four oddball 24.9K resistors. I'm just guessing that you don't have this value in your parts kit  Smiley

When this was first released back in 2019, I was lucky to find a new PCB/Panel set for only $29 (USD)!!! Unfortunately, the only ones to be found these days are pre‑assembled modules for $110 (USD). PCB/Panel sets were available for a very short time at the Pusherman website. You can check the Transient Modules website for other vendors who will (hopefully) restock this PCB/Panel DIY set someday

January 2021 Update: Pusherman has recently re‑stocked this PCB/Panel DIY set. The price has increased slightly to $39 (USD) because this is a new Version 2 PCB but... it's still a bargain for this versatile build. So far, the only major difference I can see is a new Calibration SMD pad which is used to set the LED's at optimum levels. Get the new Version 2 PCB/Panel set while it lasts here
Shelves  (Mutated)

      Panel/PCB Build Notes & Review

If this PCB/Panel set is buried deep down in your build queue... do yourself a favor and move it near the top right now!

I should never have waited so long to build my Shelves. It was last in my build queue forever because the description of a "4‑Band Parametric EQ" never really appealed to me. It sounded boring. I figured if I wanted to have any EQ that it would be added downstream in the mixing phase. Holy Cow... was I ever wrong. This module is extremely versatile! The sonic palette is vast. There are no STM IC's and there is no firmware to install so it's a very straightforward build. However, there are several SMD IC's which can be intimidating because of their small footprints. Some 0603 SMD soldering skills are definitely required. The PCB is quite crowded and I found myself taking several breaks and spaced things out over two days

Two things to make note of when ordering components are
  • There are sixty-three 100K Ohm metal film resistors and the specs for these require a tolerance of 0.1%. Not 1% like most other builds. This bumps up the build price considerably

  • There are some oddball IC's you won't find at Mouser, DigiKey or other big‑name suppliers. Three CoolAudio V2164M Quad VCA SOIC‑16 IC's are needed and you can find them at CabinTech Global for a good price with quick, low‑cost shipping

Pusherman has two high‑quality panels to choose from. Be aware that panels I've seen from other vendors do not have the six extra Bandpass OUT jacks to accomodate this extra PCB

               Link Arrow Black Anodized Aluminum Panel
               Link Arrow Pusherman Glossy Black Panel
               Link Arrow PCB + Expansion PCB

Two Nine Five  (MMI)

      Panel/PCB Build Notes & Review

This is an adaptation of the Buchla Model 295 10‑Channel Comb Filter

Looks are deceiving. At first glance it looks like an ordinary Equalizer but it's much more than that. This Comb Filter adds a delayed version of a signal to itself causing constructive and destructive interference. The crazy sound filtering you can get out of this module is impressive!
  • About 90% of all components are 0603 SMT/SMD so it takes longer than a through‑hole build. It is absolutely imperative that you solder R13, R39, R17, R37, R19, R35, R25, and R33 in place before mounting the trimpots as they will be very difficult to reach once all components are in place

  • There are eight trimpots on the back which allow individual tuning of each Band Frequency, Q's, and Amplitude. Mouser was out of stock of the red sliders at the time of my build so I opted to go with orange and it looks great sporting the 10 LED sliders. This Bourns slider pot is available in three colors
              Red: (P/N: 652-PTL20-10R0-103B2)
            Green: (P/N: 652-PTL20-10G0-103B2)
           Orange: (P/N: 652-PTL20-10O0-103B2)
  • If you purchased the Modular Addict v3 PCB (text in the upper right corner of the PCB says Modular Addict) you will notice there are no markings to show correct orientation of the diodes (D1D2) and the IC's (U1 thru U5). You can view the correct orientations for the v3 PCB using this PCB image or reference the PCB image shown at the MMI Modular Github webpage

  • The BOM shows a pricey SMT 10‑Pin Power Header. I'm notorious for being a cheapskate so whenever possible, I try to use inexpensive parts at hand and modify. I took a 20¢ Double Row Pin Header and used small needle‑nose pliers and bent the pins at opposite right angles. It worked great but soldering that part was a slight challenge because of the tight quarters. Even if you use the expensive part, this component will be a tricky soldering job


You can listen to some Two Nine Five demos here
         EUROCRACK MMI Modular Webpage

The PCB/Panel set is available for purchase at Pusherman and also at

LFOR  (ST Modular)

      Panel/PCB Build Notes

This is a module in my setup which gets a LOT of use. After using it for several songs, I found it was so versatile that I ended up buying two more. It is very compact at only 4HP but offers many features for such a small module. It sends out three voltages in Pulse, Triangle and Random shapes. It generates random patterns and random triggers and it's easy to manipulate using the three CV inputs of RATE, RESET & RANDOM. The Random Lock toggle switch adds a nice touch for creating repetitive random patterns. An oxymoron? Not really!

This build was inexpensive and extremely easy with a very low parts count. I paid less than $35 (USD) for the PCB, Panel and all components. Some of the components are very small 0603 SMD sized so it's recommended that you have some basic SMD soldering skills before attempting this build

The PCB has an EEPROM IC on‑board which needs to have firmware installed but this is a fairly simple procedure. I was completely unfamiliar with installing firmware on a Eurorack module but figured it out right away. I have posted a one page instruction "cheat sheet" below which is simple and easy to follow. You will need an AVR Hardware Programmer and some free software. Don't panic! This extra gear is not that expensive and you will no doubt get hooked and be using this same programming hardware for future Eurorack builds such as GRIDS, EURO KASTLE, BRANCHES & more

               GREEN_LINK_ARROW My Firmware Installation "Cheat Sheet"
               Link Arrow BOM + Firmware
               Link Arrow Mouser Cart

     SPECIAL NOTE: The Mouser Cart does not include these parts which you can source from or eBay
          (Quan: 6)  SKU: A-2563 - PJ-3001F 3.5mm Mono Phone Jack
          (Quan: 1)  SKU: A-1848 - 100K Ohm Linear Taper Potentiometer Round Shaft 9mm
          (Quan: 1)  SKU: A-1851 - 100K Ohm Linear Taper Potentiometer Knurled Plastic Shaft 9mm
          (Quan: 1)  Knob - Your Choice. I recommend one with a set‑screw such as the Davies 1900H SKU: A-4564
          (Quan: 1ON/OFF/ON Sub-Mini Toggle Switch (Note: Pin spacing for this switch is 2.54mm... much smaller than a normal toggle switch)

The PCB/Panel set is available for purchase at Pusherman

TRIPLE SLOTH  (Nonlinear Circuits)

      Modification: Changing It To A TORPOR x3 Module

The standard Triple Sloth module has three separate Sloth Chaos circuits and each one runs at a different rate to travel around 2 strange attractors

TORPOR:  15‑30 Seconds
APATHY:  60‑90 Seconds
INERTIA:  30‑40 Minutes

My style of music can't wait 30-40 minutes so I decided to turn my Triple Sloth module into three TORPORS. The modification is very easy by simply changing one potentiometer and some resistor and capacitor values. With help from Andrew at Nonlinear Circuits and member PnP Modular in the Nonlinearcircuits Builders Guild on Facebook, I have compiled a spreadsheet with the new quantities, component values and my build notes

               Link Arrow Triple Sloth BOM Modification for Torpor x3

The PCB/Panel set is available for purchase at Nonlinear Circuits

CVpal  (Mutable Instruments)

      Errors When Installing Firmware

I was unable to use the fancy commercial program ATMEL STUDIO to install firmware on my CVpal and the ATTINY84A EEPROM. I kept getting errors when trying to use the Mutable Instruments recommended settings for the Fuses and Lock Bits

                     EFuse: 0xFF              HFuse:0xD6              LFuse: 0xDE              Lock Bit: 0x2F

I eventually gave up trying to use ATMEL STUDIO and finally succeeded by using the command line program called avrdude

Here are my notes showing how I finally made everything work

               Link Arrow CVpal Firmware Installation Notes

The PCB/Panel set is available for purchase at Modular Addict and Pusherman

The next four modules (Grains / Mini Pops / Plancks MK2 / SPIN FV‑1) are included here so that others are able to get their builds working. Some of these were especially difficult to build and program with firmware. SPIN FV‑1 is up and running with FX but it's not quite there... almost
Grains  (GinkoSynthese)

      Repair Notes

I was unable to find any detailed documentation about installing the firmware for this module. This was way back in 2018 so I chucked it in a box and decided to work on it later. Two years later I finally got it working after finding a post on Facebook. After reading some posts from others who have never been able to make their module work, I decided to compile my notes which might help them

The main problem I had was with the Arduino Nano board which was bundled in the Full DIY kit. It was un‑configured, blank, broken, brain dead or all of the above and it needed to have a special bootloader reflashed/repaired/installed before it would work. I'm not sure if this is by design of if there was a bad batch of boards from the factory. Just to make sure we don't get confused here, there are actually two Arduino boards being used in this repair process. The Arduino Uno Board which is used to repair the Arduino Nano board and the Arduino Nano board which is part of the actual Grains module assembly

These are the steps I took to finally get my module up and running
  • Purchased an Arduino Uno board. The cost is about $10 (USD) and looks like the board in Figure 1
  • Purchased a Type‑A to Type‑B USB cable. Looks like this and is used with the Uno Board
  • Purchased a Type‑A to Mini‑B USB cable. Looks like this and was bundled with my Grains DIY kit
    • This is required for installing firmware on the Nano Board
  • Purchased a set of Dupont Female to Male jumper wires. Looks like this and are available at
  • Downloaded the free Arduino IDE software (Mac or Windows ‑
    • This software is needed to Reflash/Repair/Install the bootloader and install firmware into the EEPROM IC on the Nano Board
  • Reflashed/Repaired/Installed the bootloader on the Nano Board's EEPROM IC
  • Installed Grains firmware on the Nano Board's EEPROM IC via Type‑A to Mini‑B USB cable
Figure 1
Model# Arduino UNO R3 MEGA328P

No easy task. A lot of steps and some extra cost, for sure. The price of my $62 Full(?) DIY kit jumped way up

A broken bootloader on the Nano board is (I think) what some current Grains owners are having issues with. There is a very good video inside the link below which covers the procedure for reflashing/repairing/installing a broken bootloader. Basically, you are connecting wires from the Uno Board to the Nano Board, rebuilding/repairing a new bootloader for the hardware and installing new bootloader EEPROM code. I would recommend skipping the first three steps in the YouTube video and start at Step #4 - Missing Arduino Bootloader

After reflashing/repairing/installing the bootloader (as shown in the video link below), disconnect the Uno board from everything and plug a Type‑A to Mini‑B USB cable from your computer into the Nano Board on the Grains module. Run the Arduino IDE program and upload a new firmware file (there are several to choose from at the GinkoSynthese website)

The settings I used from the Arduino IDE drop‑down menu to load new firmware (these must be done in order)
  • Tools    Board    Arduino AVR Boards    Arduino Nano
  • Tools    Processor    ATmega328P
  • Tools    Port    (Your Serial Port)
    • On a Mac it shows up something similar to   /dev/cu.usbserial-1410
    • On a PC something similar to  COM4
  • Tools    Programmer    Arduino as ISP
  • File    Open    (Choose a new firmware file. This will be something similar to pwm-saw-vca-vcf.ino)
    • This firmware file must have the extension of *.ino
  • Sketch    Verify/Compile (returns with the message "Done Compiling")
  • Sketch    Upload (Returns with the message "Done Uploading")

  • If there are no errors returned, unplug USB cable from the Nano Board, plug the Grains module into your Eurorack case and test the new firmware

Note: If you are working on a Mac, you can probably ignore the section about USB drivers. Unless you are still working on a system with an older O/S, Mojave 10.14 or later (October 2018) already includes a CH34x USB driver by Apple. If both Apple's and the new OEM's drivers are installed, they will create conflicting non‑functional serial ports. If you are unable to select a valid serial port on a Mac or a PC then you may need to install these extra Serial Drivers after all (refer to the video link)

               Link Arrow Reflash/Repair/Install Bootloader Instructions (With Video)

Interesting side note: Someone ported Mini Pops firmware code and modified it to work with this Grains module. I have installed it on Grains and it sounds very cool. It's a little harder to manipulate than the original Mini Pops because there are no switches to turn individual instruments On/Off but it does have more advantages of being able to controll the instruments, patterns and tempos by CV Inputs and/or Pots. This alternative firmware for is available for download from the EMast42 GitHub  webpage
Mini Pops  (Old Crow Modular)

      Panel/PCB Build Notes

UPDATE - June 2021:  I have confirmed with someone else who has built this module that he is getting the same terrible muffled and lackluster sound as I am. Something with this module is definitely off. Bad design, bad firmware or both? Dunno. I don't recommend purchasing this module with the firmware that's available and ZERO support from the designer. If you already have the PCB/Panel, here's the scoop

The original Korg Mini Pops 7 is famous as one of the rhythm machines featured on Jean‑Michel Jarre LP's titled "OXYGENE", "EQUINOXE" and "THE CONCERTS IN CHINA". There is a detailed webpage about the original rhythm machine here

I finally found a copy of the firmware and BOM from a source and was able to build the module. There was no build documentation and no firmware posted online anywhere and I had some requests for info about it from other builders. My build sounds nothing like an original Korg Mini Pops 7. The Audio Out is muffled and unpronounced

I have assembled some images and text files with my build docs, bootloader + firmware files, Mouser Cart, BOM and firmware installation instructions using an AVRISP MKII Programmer with Atmel Studio v7 ‑or‑ a TL866CS EPROM Burner with TL866A/CS Application Software. Both are for use on a Windows PC

Abbreviations for instrument sounds on the panel might not be apparent at first glance. They are
   QU = Quijada
   CY = Cymbal
   MA = Maracas
   CW = Cow Bell
   CL = Claves
   BD = Bass Drum
  BG2 = Bongo
   GU = Guiro

I found this build to be extremely challenging because
  • There are no schematics, no build documentation and no BOM online for downloading
  • The designer (Old Crow Modular) has not answered any of my support eMails for any modules dating all the way back to 2017
  • And yes... I was stupid enough to buy it anyway. I do like challenges

All of these files and images will all be placed in one *.ZIP file for easy downloading. Someday. For now, easier for me to update

               GREEN_LINK_ARROW My Bootloader/Firmware Installation "Cheat Sheets" And Miscellaneous Build Notes
               Link Arrow Bootloader + Firmware + INO
               Link Arrow Populated PCB    
               Link Arrow Original Korg MP-7 Schematic
               Link Arrow BOM
               Link Arrow Mouser Cart   (Note: Nine Toggle Switches Three Mono Jacks, Two Pots & Two Knobs Are Not Included)                     

     SPECIAL NOTE: You can source these parts from
          (Quan: 3)  SKU: A-2563 - PJ-3001F 3.5mm Mono Phone Jack
          (Quan: 2)  SKU: A-1847 - 10K Ohm Linear Taper Potentiometer Round Shaft 9mm
          Search eBay for the sub-mini toggle switches and knobs

Interesting side note: Someone ported Mini Pops firmware code and modified it to work with the GinkoSynthese Grains module. I have installed it on Grains and it sounds very cool. It's a little harder to manipulate than the original Mini Pops because there are no switches to turn individual instruments On/Off but it does have more advantages of being able to control the instruments, patterns and tempos by CV Inputs and/or Pots. This alternative firmware for Grains is available to download at the EMast42 GitHub  webpage
Plancks MK2 8HP - a.k.a. Frames  (Jak Plugg)

      Firmware Installation Notes

I was a noob when I installed the firmware on this module so it wasn't very easy for me starting out from scratch. I have put together a one page instruction "cheat sheet" which should make installing firmware on this module easy for any beginner

               GREEN_LINK_ARROW My Bootloader/Firmware Installation "Cheat Sheet"
               YELLOW_LINK_ARROW STM32 ST-Link Utility (STW-Link004) (Windows Software)
               Link Arrow frames_bootloader.hex (Frames Bootloader Download)
               Link Arrow frames.hex (Frames Firmware Download)

The PCB/Panel set is available for purchase at Pusherman
SPIN FV-1  (mxmxmx)

      Firmware Installation Notes

The designer of this module has a minimal build guide for this one. What an understatement. This was a very difficult build due to lack of documentation. The BOM is missing some parts and there is virtually zero info re: how to install the firmware for the internal ATtiny85 EEPROM or the external 24LC32A EEPROM. If you like a challenge... buy this PCB/Panel set. You won't be disappointed. I'm posting this here for anyone else struggling to get it working. I've been able to get the eight internal programs on the SPIN FV-1 ROM working just fine but still have not been able to load any custom code into the external EEPROM. The code I was able to load on the internal EEPROM is very basic. The purpose of this code is to cycle through the eight FX programs contained on the SPIN FV-1 ROM. I will update this page If/When I figure out how to send custom user code to the external ERPOM someday. It's working as‑is using the PRG button and it can access these eight FX programs
     0 Chorus/Reverb
     1 Flange/Reverb
     2 Tremolo/reverb
     3 Pitch/Shift
     4 Pitch/Echo
     5 Test
     6 Reverb 1
     7 Reverb 2

The input jack labeled BL accepts CV signal inputs and will vary the amount of BLEND between a dry signal and the currently selected FX. The three CV inputs and three potentiometers labeled 1, 2 and 3 are non‑functional at the moment. My guess is these will only work if custom firmware is installed on the external EEPROM. Likewise, the BL CV input currently has no effect on any of the CV inputs 1, 2 or 3

Extra parts needed for this build not shown on the BOM are

     (1) 10uH Inductor - Mouser P/N: 810-MLF2012E100JTD25
     (1) Tact Switch Cap - Mouser P/N: 642-1SS00-15.0 (this P/N is blue but is also available in green, grey, yellow, white, red or black)
     (1) 32.768KHz Crystal - Mouser P/N: 732-C002RX32.76K-EPB

Items needed for installing firmware on the ATtiny85 EEPROM are
  • Arduino UNO board. It costs about $10 (USD) and looks like the board in Figure 1 (see the Grains module above)
  • Type‑A to Type‑B USB cable. Looks like this and is used with the Arduino Uno Board
  • Set of Dupont Male to Male jumper wires. Looks like this and are available at
  • Project Breadboard. Looks like this and is used to program the ATtiny85 IC
  • Free Arduino IDE software (Mac or Windows ‑
    • This software is needed to program the ATtiny85 IC
    • A one‑liner from the mxmxmx docs says this can also be used to load custom user EEPROM code. So far... no luck
I was unable to program the ATtiny85 IC while it was plugged into the SPIN FV-1 PCB. I had to remove it from the socket, place it on a project breadboard and wire it up to an Arduino UNO Board. I used the instructions at the website which were very precise and detailed. This method worked the first time without any issues. Instead of using the "Blink" example code, you will need to use the firmware file downloaded from the mxmxmx Spin FV-1 Github page called spin_attiny.ino. Once the ATtiny85 IC is programmed with this new code, pop it back in the socket on the SPIN FV-1 PCB. This code you just installed is what activates the PRG button so it can step through and access the eight internal FX programs

Figure A
Jumper "i" For Internal Patches
(click for larger image)

SPECIAL NOTE: Before you can use any of the internal programs in ROM, you will need to set a jumper for the 3-pin header on the backside of the PCB. This position is shown on the silkscreen as a lower case "i" (See Figure A)

               Link Arrow mxmxmx Spin FV-1 Github Page / Build Guide + Firmware

PCB's and Panels are available for purchase at Pusherman

               Link Arrow Spin FV-1 Panel
               Link Arrow Spin FV-1 PCB

Favorite DIY Tools And DIY Vendors

Tips For DIY Freaks Who Like To Save $$$. I picked this selection of gadgets and vendors because of the extremely LOW cost. I use everything shown here almost every day and highly recommend each one

               Link Arrow Favorite DIY Tools And DIY Vendors

Safety Precautions and Disclaimer
Modifications made to any factory stock equipment will always pose an element of risk. Sometimes mistakes are made which are irreversible. Improper soldering and handling of electricity can cause serious injury and damage the synthesizer. Use caution when handling static sensitive devices and the PCB. Make sure you are properly grounded, working on a static‑free workbench or table and wearing eye protection during any soldering tasks. The author is not responsible for any damage or injury resulting from this DIY info. Use this DIY information at your own risk. And, I can't stress enough, the importance of wearing eye protection while soldering. That stuff flies everywhere sometimes!

ANIMATED_STAR I think these two topics are important enough to place on all of my synth INFO webpages


1) I buy a lot of broken synths on eBay and I'm able to fix about 90% of everything I find. It's usually a simple fix. If you have a synth with no power or intermittent problems after it warms up, it's probably due to the fact that back in the 1980's Roland and other synth makers used sub‑par solder and/or not enough solder to hold components in place. After 30+ years, the solder begins to break down and hairline fractures appear. This occurs at a higher rate for components which generate a lot of heat like Bridge Rectifiers, Power Transistors, large Electrolytic Capacitors, power input jacks and audio sockets which get a lot of use. The best approach is to use a magnifying glass and carefully inspect the backside of the circuit board. If you spot any suspect areas, re‑flow a hefty amount of NEW solder

2) I receive a lot eMails and field many questions at synth related forums and also on Facebook. The most common question I get about problems with a synth has to do with errors when trying to load Patches and Tones. About 99.9% of the time, the problem always turns out to be a crappy MIDI interface. If you have a cheapo MIDI interface which looks similar to the one shown on the right... throw this piece of shit in the trash! Do It Now. Seriously! This thing is total junk and you get what you pay for. Inexpensive MIDI interfaces like this are unable to properly regulate the buffering of MIDI data. They will work fine with simple messages such as CC, Note On, Note Off, etc... however, when you try to send SysEx messages which are much longer, the SysEx data cuts off after only sending a few bytes. Investing in a higher quality MIDI interface will solve Load/Save errors and other communication problems

Other Synthesizer And Sampler Homepages I Maintain


If you find some of this DIY info useful, please consider donating a small amount. All donations are used for future DIY synth development. Thanks! SUPER-JX ZONE

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