Friday, July 14, 2017

An Unofficial Build Guide for a MIDIBox Seq V4

Disclaimer: I am in no way affiliated with MIDIBOX.ORG, and I do NOT profess to know all there is to know about the MIDIBox Hardware Platform. To the best of my knowledge, all the information contained herein is accurate.  My own SeqV4 is not complete, and this page will be updated as I make progress.  Email questions, comments, and corrections to

This is a DIY project. If DIY is not for you, join the MIDIBox Forum (find link below), visit the Flea-Market, and find a pre-built unit for sale that will fit your needs. 

Updated 17 July 2017 - added female IDC connectors to relevant parts lists and added link to connections diagram in Line Driver section

Updated 23 July 2017 - changed electrolytic capacitors in AOUT_NG kit to better fit layout and lead spacing

Updated 08 August 2017 - MODULAR ADDICT NEW SOURCE FOR MIDIBOX PCBS INCLUDING CS BOARD PCBS!!! SEE BELOW....  plus a suggestion added to Core Board build if adding a Quad_IIc_MIDI board

Updated 02 October 2017 - Modular Addict now also carries "Waldorf" knobs and data wheel (see below), and I've added notes to the CS Board section with regards to bottom-mounting the Data Encoder

Building a MIDIBox Seq v4 requires a bit of research…. All the information is available on the internet, but it can be confusing and overwhelming when you first approach the project, especially as there is no ONE WAY to build.  “MIDIBox (or MBHP)” is the name of the hardware platform, “SeqV4” is the name of the application, and there are many possible hardware configurations and parts selections available so every device can be uniquely customized.  The goal of this guide is not to examine every possible option, but to simply help others get a head start if they are considering building a MIDIBox SeqV4, whether that be a minimal, midi step sequencer or one like mine which has a few more options.  I do not intend to create guides for any peripherals which I have not built (and tested) myself.  This document compiles relevant links and information from multiple sites in an effort to make it easier to understand and navigate the process of designing and building your own MIDIBox SeqV4.    

(One of the hurdles that I cannot remove is the availability of PCBs.)  
Player 2 has joined the game! has started stocking a near full range of MIDIBox pcbs!  Prices there are basically the same as they have always been at MIDIBox Shop (they all look to be $.01 cheaper, except the Core which is $1 more).  Most have been sporadically available from the MIDIBox shop (, but some (like the Line Driver Tx and Rx boards used to boost signals sent to an optional breakout unit for CV/Gate, etc) you may need to have fabricated at OSH Park (, or you may be lucky enough to find someone on the MIDIBox Forum ( who has a few extra to offload.  You could also make your own circuit boards if you are inclined and determined as schematics are available for each board!  Some older boards are still available at Mike's Midishop (

The MIDIBox shop also offers some parts kits, some ICs (some can be purchased pre-programmed), and has offered connectors in the past (I don't see any available on the site as I write this, but I did purchase DIN connectors there when I bought some PCBs in 2016).  These kits are good value, however if they are not available, I have links to Project Files at Mouser for each module which will save you from finding all the parts you need yourself.  (Mouser has several ways to save lists of parts for different projects: BOM, shared carts, project files, etc, but I will me using the Project File level. These allow you to load a project, click "order project" to send those parts to a cart, then load another project to purchase more in the same order. Sharing BOM would still require you to select individual parts, and sharing carts makes it difficult to purchase more than one project in one order. So if I use the term Project File or Kit, I am referring to the Project File level of saved files in my Mouser account.) Of course, some parts may be unavailable or out of stock at Mouser, cheaper from other distributors, or not the highest quality available, so if you want to shop around, you will at least have the specs about each part in my project file. For example, the Switchcraft brand midi sockets in my Mouser carts are $2.93 each, but you can get CUI,Inc. brand midi sockets from Digi-Key for $1.02 each.  As my build uses 12 sockets, that's a difference of $22.91, but you'll want to compare the savings you will get to the cost of additional shipping fees.  Obviously it made sense for me to place two orders from different distributors, but for the sake of simplicity, I have created carts that source all parts from a single distributor (per MBHP module).  Honestly, Digi-Key has better prices on DIN (midi) connectors and IDC headers/connectors, so if you are on a tight budget, it may be worth the effort to make a list of these parts from each module of your planned build, remove them from the Mouser Project Files, and order them all at one time from Digi-Key.  

There are some parts that are customizable in the sense that you might want a specific knob style, LCD color combination (or even OLED or VFD), LED shape, etc., so keep this in mind when reviewing my BOMs or project files and when deciding on a front panel or enclosure design (my build uses rectangular LEDs, but my kits contain the more common round LEDs instead).  Check the forum for a post about a new Seq V4+ control surface PCB, panel, and software before committing to a case, panel, or control surface (CS) board. 

The main page for everything MIDIBox related is  Admittedly, this page can be a bit overwhelming if you are just starting your build, but almost everything you need to know (and a ton more) is on this site.  Much of what I am doing in this write-up is taking links from this site (and a few others like that are relevant to building my Seq V4 and introducing them in a way that might have made more immediate sense to me when I started my build.  Also check out 

What Do I Need?

Anyone building a Seq V4 will need at the least:

-        a “Core” module…. This is the center of the MBHP, or MIDIBox Hardware Platform, which hosts the CPU board (purchased separately) and links to all the optional peripherals.
-        a CPU (referred to often as the “discovery board” or by the model number, like STM32f4)
-        a MIDI IN and/or OUT interface (most likely, and often more than one)
-        a control surface (Wilba’s CS, the future V4+, or DIY)
-        displays
-        a case or front panel
-        USB cables and SD Card (the SeqV4 can be powered via USB, but cables are also needed for programming and firmware)
-        a computer running freeware to flash and update MIOS (MIDIBox operating system)
-        soldering equipment and various tools

You, like me, may opt to include other peripherals:

-        an analog output board for CV outputs
-        a “digital” output board for gates, clocks, triggers, etc.
-        a set of boards to transmit and receive signals from the MIDIBox enclosure to a breakout box or panel
-     external power supply

And you may choose to add other options which I have not built:

-        4x16 X0X-style button array
-        Tempo display
-        Track position display
-        And more….see the left-hand column on under “MB Hardware Platform”…but keep in mind that not all peripherals are necessary with every Core variant

 My build includes the following:

-        STM32F4 based Core with STM32F407G* Discovery Board CPU
* it is essential that your discovery board have the suffix 07G
-        ST-Link, MIOS32, and SEQ v4.092 software
-     Wilba CS Board 
-        MIDI I/O module (x2)
-        Quad_MIDI_IIc module
-        DOUT digital output module
-        AOUT_NG analog output module
-        Line Driver transmit and receive module
-        LCDs 
-        Custom laser cut case (modified design based on the Mongbox)
-        Breakout box with custom output PCBs
-        Power receptacle, switch for AC adapter, and internal 5V regulator (Adafruit)

STM32F4 based Core

I chose to use the STM32F4 Core mainly for its availability, although it seemed like the best choice at the time of writing.   An STM32F407G Discovery Board (the CPU) mounts to the Core PCB and is programmed using freeware (this is much easier than it might sound).  Be sure to purchase the 07G version of the STM32F4!

I bought the Core PCB from MIDIBox Shop, and a parts kit is often available there as well.  At time of writing, the Board alone is $9, while the Kit + Board is $34 (neither include shipping, all ROHS compliant).  My MBHP_Core_STM32F4 project file at Mouser totals about $52 plus shipping, includes all parts from the Shop’s Kit plus the STM32F407G Discovery Board ($19+) and 5’ of 16-conductor ribbon cable, but some parts may not be ROHS compliant.  Some parts in my kit are currently cheaper from other distributors: the IC sockets, shrouded IDE headers, and 2x25 female headers.  If you order the MIDIBox Shop Kit + Board, you will still need to order the STM32F407G and ribbon cable!  However, these item can be added to a future order, you don't need them to build the Core.

Neither the Midibox Shop kit nor my Mouser cart contain the required SD card (2GB) or USB cables as they are far too expensive when sourced from distributors like Mouser.  The cables can probably be purchased locally, and the SD card from eBay or Amazon. 

Diagrams of connections and assembly/programming instructions are available on the main page for the STM32f4 Core, scroll down to the relevant section: 

Note the need to update firmware on discovery boards marked with MB997D

The discovery board can be programmed before the Core Module is built.  The bootloader and application software current at time of writing is also linked below.  Once your Core is built and the discovery board is coupled to it, you may want to connect your chosen display screens (see below) so you can verify that the software is correctly installed and that the SD Card is recognized. 

Until you decide on how your boards will be mounted and the style of your enclosure, I suggest you leave the mounting lugs off the board.  You may find later on that the legs are too long or that they obstruct the holes on the PCB should you choose to use stand-offs.  Also, I don’t know if the older STM32 boards had the same dimensions, but my STM32F407G hangs over the edge of the Core board, so the lugs would not fit flush against the inside of the case.  You would need to include a washer/spacer between the case and the lug to prevent putting stress on the discovery board.

NOTE:  If you plan to use the Quad_IIc_MIDI module as your MIDI output, you may want to use a different connector on the Core at location J4A or J4B. The Quad_IIc only requires four pins to connect to the Core, and a 10-pin header does not fit well on the Quad_IIc board.  Had I known I wanted to add a Quad_IIc to my project when I built my Core, I would have ordered something like this to connect the two boards:

This part is not included in the parts kits!!


My FULL Mouser Kit

Adafruit Power and USB parts : 

  - USB cables :
  - 5V DC/DC convertor :
  - DC Power Connector :
  - DC Power Extension :

Schematic/Dimensions/Image/Software/Parts List

Display Screens

At this point, you may want to connect some displays so you can verify that things are working properly.  As this is my first SEQv4 build, I'm choosing to keep things simple with regards to the display screens to start with, so I am just using backlit LCDs.  As I'm using the Wilba CS board and a Wilba-based panel design, I'm also using the standard 40x2 character displays.  The 40x2 LCDs must be Hitachi HD44780 compatible as MIOS supports this format internally.  When searching for LCDs, its easiest if HD44780 is mentioned in the specs (but there is a list of possible compatible drivers on the wiki page,  I ordered mine from a Chinese source on eBay, and while they were quite cheap, they took about 6 weeks to arrive!  As of writing this, Mouser and Digi-Key do not have an affordable screen on the compatibility list. 

In addition to the screens themselves, you will need two 2x8 male IDE headers which you will solder to the PCBs that the LCDs come mounted on, and four 16-pin female IDC connectors to connect the LCDs to the Core Board.  You should have all these if you ordered my FULL cart for the Core or the Discovery and Ribbon cart above, but if not, add those to your next Mouser order.  

NOTE: If you are making a custom enclosure (or building a Mongbox or my variation of the Mongbox), you may find it necessary to use "right angle" headers on the LCD units to reduce the depth from the front panel, or perhaps even to solderi the ribbon cable directly to the LCD PCBs.  Using straight headers and connectors in a shallow enclosure will likely interfere with your "rear panel" modules like MIDI connectors, serial connectors, etc.  Of course, if you only plan to have one MIDI_IO module and a Line Driver, you can probably place those modules under the LCDs in such a way that they have plenty of clearance.

Some people have chosen to use OLED or VFD displays which may take a bit more work to get going, so search the MIDIBox Forum for posts about these options if you are leaning that way.  I will say, they look fantastic!  You can always change the type or color of display anytime.  

More info on MBHP LCDs here, but only read this if you are really interested in using something other than a 40x2 screen:

eBay search result for HD44780 40x2 LCD


The MIDI_IO module is a 2In/2Out midi interface that can be chained to include up to 4 modules giving you 8 MIDI in ports and 8 MIDI Out ports!  Of course, you’ll need a pretty large panel to accommodate four of these modules.  There are some other MIDI I/O options, like the IIc (1 in, 1 out) and the Quad_IIc (4 outs, space for a DIN Sync socket, and the 8-pin DIN socket and circuitry for the BLM).  My build includes two MIDI_IO modules and one Quad_IIc for a total of 4 Ins, 8 Outs (I’m not using the BLM at this point). The MIDIBox Shop PCB alone is $7, the Kit & Board is $27, and my Mouser cart is $22.47 today. Again, the MIDIBox Shop kit includes the mounting lugs, as does my mouser cart, but I suggest you leave these off the PCB until you have decided on a case design. 


Schematic/Dimensions/Image/Parts List

Dimensions: 102.8mm x 43.9mm

Shown without BLM and Aux DIN options installed

As mentioned above, the Quad_IIc_MIDI board adds four more MIDI outputs as well as the BLM port and a place to mount another 5-pin DIN connector for DIN Sync (I’ve seen this described as an Input, but I’m not sure, need to find more info).  I've never seen a kit available at the MIDIBox Shop (although the link below goes to a page that suggests otherwise), only a PCB and the programmed PIC16F88 chips, but I have put together a Mouser cart for the rest of the parts which you can order or just use as a reference.  You may decide to search for a different DIN socket (these have a silver face), but keep in mind that not all sockets are built the same.  The all-black sockets I considered had a different measurement from face to front leg which would have set my Quad_IIc PCB back further into my case causing it to collide with my Core PCB.  The DIN socket is one of the parts that I found to have a wide range of costs depending on the distributor, from $1/each to $4/each!  You may want to check the MIDIBox Shop to see if he still has some sockets available when you order your PCB.  The BLM/DIN section of the PCB could actually be cut off and separated from the MIDI port section as the circuits are fully independent, but the mounting holes on the PCB aren’t designed for this, you may need to modify.  The Quad_IIc PCB from MIDIBox Shop is $9, the programmed ICs are $3.95 each (total of 4 required), and my Mouser cart is $27.61 (I have not yet decided how I will connect the Quad_IIc to the Core's J4 header, so these connectors are not yet included in the kit).  Of course, if you don't plan to populate and use the BLM and "Aux DIN" part of the board, you can omit the parts listed as "optional BLM connection parts" on the following page:


Schematic/Dimensions/Image/Parts List

Quick View -


Parts List from MIDIBOX Shop:  

| IC1x  | IC-Socket for 16F88                |  4  |
| LEDx  | 3mm LED red                        |  4  |
| Q1x   | 20mhz crystal                      |  4  |
| C3    | 10µF Electrolytic capacitor        |  1  |
|C1x,C2x| 15pF Ceramic capacitor "33"        |  8  |
| C4x   | 100nF=.1µF Ceramic capacitor "104" |  4  |
| R2x   | 220Ω resistor               |  4  |
| R9x | 220Ω resistor               |  4  | 
| R10x  | 220Ω resistor               |  4  |
| --    | 5 pin DIN connector                |  4  |
| J4    | 1x4 pinheader                      |  1  |
|-------|---optional BLM connection parts----|-----|
| IC2   | 6N138 optocoupler                  |  1  |
| IC2   | IC-Socket for 6N138                |  1  |
| R6    | 1KΩ resistor               |  1  |
| R7    | 4.7KΩ resistor                     |  1  |
|R8-R10 | 220Ω resistor               |  3  |
| D1    | 1N4148 diode                       |  1  |
| --    | 8 pin DIN connector                |  1  |
| --    | Box Header 2x5                     |  1 

Dimensions: 135mm x 46mm

SEQ CS (control surface)

Note: shown with data encoder top-mounted!

The Seq CS Board is the user interface for the SeqV4 application. (and also the largest and most difficult board to acquire for the SeqV4 project.  I don't check the MIDIBox Shop everyday, but I do quite regularly, and I have only found the board to be in-stock ONCE.) There is some talk of the development of a V4+ on the MIDIBox Forum, so you may want to follow the discussion there for progress and availablitiy.  You could create your own control surface on perf-board or by designing your own PCB for fabrication, but unless you also plan to design your own panel, waiting for a Wilba CS board from the shop or from the Forum's marketplace is your only option. Building the CS Board requires a handful of ICs, dozens of push-button switches, diodes, and LEDs, 17 rotary encoders, and a few other parts.  The MIDIBox Shop offers (when available) the CS Board PCB for $35 and a parts kit for $120 (sold separately) which includes all the parts necessary including P401 knobs except the data wheel. However, this kit has not been in stock for quite some time, I believe due to the lack of availability of one of the parts. Rather than wait for the kit to be in stock and then have to spend $120 in one go, I chose to source the parts myself, buy a little bit at a time to spread the payments out, and change some of the parts to fit my case design. 

For my own build, I chose to use 2mm x 5mm rectangular LEDs rather than the more common 3mm round LEDs, which required a modification to Wilba's front panel design. However, my cart for this module will contain 3mm round, so keep that in mind when looking at photos of my finished build (whenever that happens) or if you should decide to use my case redesign (a variation of the Mongbox design by forum user Mongrol).  You will either have to modify my case for 3mm round, or order rectangular LEDs instead.  

Even with 3mm round LEDs, there is some room for customization.  I imagine most people use the typical, dome-topped LEDs which is what I have included in the kit, but I would prefer to have flat-topped LEDs mounted flush with the faceplate.  

The Wilba panel is designed for a certain type of button cap, the type included in this cart, but if you plan to design a custom front panel, you can use whatever type of button or cap that you like.  I have seen round, square, and even illuminated while checking out other people's builds on the forum.  The current CS board has multiple hole patterns for each button/tact switch so a variety of models can be used.  The tact switches I used were relatively affordable, but you can probably get some fancier and more rugged switches if you want to search for advice on the forum.  As this is my first build and I am on somewhat of a strict budget, I decided to use a cheaper alternative. I can always upgrade at a later date.  

The encoders are another part that is not limited to only one model.  There are a few brands to choose from, some with push-button function and some without. Some users have commented about more reliability with certain models, so check the forum for the latest reports. The encoders should have 24 detents, but the push-button feature is optional.  You can adjust settings later somewhat to accommodate the encoders you choose and how they perform (I am not at this stage yet, so am not speaking from experience).  

NOTE: I realized once I received my prototype case and data wheel that I should have mounted the encoder UNDERNEATH the PCB instead of soldering to the top-side like the other encoders!  If you want to use a regular knob for your data encoder, then this isn't a problem. But I wanted to use the "jog/alpha/scrub wheel"-style knob like on my Waldorf MWxt!  As I'm always in a rush to do things and couldn't settle for ordering a replacement encoder, I disassembled the installed encoder and desoldered it from the PCB.  After reassembling, I found two nuts on some other pots I had laying around and mounted the encoder to the board using one nut as a spacer and one to secure the encoder in place.  I added a short piece of insulated wire to help hold the encoder in place and together and added some clipped LED legs (removed from the bicolor LEDs which didn't need them) to connect the terminals back to the solder pads.  Now the data wheel sits at a perfect height and still allows room for the push-button function. 

ALBS DK38 data wheel
Finally, the knobs and data wheel that you choose are a matter of taste.  Of course, they need to match the shaft style of the encoders you choose, knurled encoders won't accept a D-Shaft knob.  At this point, I have yet to purchase knobs as the ones I want are still out of stock, but Modular Addict now offers some knobs that might suit some builders.  They also offer a data wheel (ALBS DK38) which I have chosen to use for my sequencer.  It is taller than some others I've seen (like the one from Adafruit which is very short).  You can find the Modular Addict option here.  

My Mouser kit for this module includes the rotary encoders (Bourns 20mm with switch), the tact switches (E-Switch brand), switch caps (see additional part numbers below for some optional gray and red caps for the transport controls), a flat-top 5mm "Beat" LED, all caps, resistors and arrays, 3mm LEDs, diodes, sockets, chips, and headers.....but no knobs or wheel.  I figured that the selection of knob style should up to the individual builder.  You'll need to select a 6mm D-shaft knob with no indicator, but the color, material, and shape is up to you.  Likewise, the data wheel you choose should be for 6mm D-shaft, but the color and diameter is a matter of taste. Note that some data wheels will sit high on the shaft of these encoders, so some modification may be required.  All the 3mm LEDs in my kit are bi-color, so you will need to remove one leg and bend the remaining two slightly to align with the panel.  Follow this datasheet for the bi-color LED for proper installation:

I made my LED cutouts very tight, only about 0.1-0.2mm clearance, so I beveled the underside of the top panel around each LED hole to help the LEDs realign properly when I have to remove the panel using a Dremel-type rotary tool.

More Info :


My Mouser Kit

Mouser part numbers
Gray Cap  -  611-PEGY
Red Cap  -  611-PERD
2x5mm Rectangular Bicolor LED - 604-WP119EGWT


Panel / Enclosure

Forum member Mongrol designed an acrylic case called MONGBOX for the STM32F4-based SeqV4 and made the files available for others to use to make their own if they or someone they know have access to a laser cutter or if they want to order from a company like Ponoko.  This is the design that I adapted to build my case, but there was an issue with the scale.  See the "scale fixed" version of the file.  I advise that you have whoever will cut your case verify that the measurements are correct when they load the file on their machines! Neither Mongrol nor I assume responsibility for any mistakes!

Mongbox enclosure thread :

Mongbox build thread :

Mongbox files :

Original panel style

The original MIDIBox SeqV4 used an older Core which did not have built-in USB, SD reader, etc, so this design does not work properly with an STM32F4-based V4, but here's a link to a set of panels for that case style:

There are DXF and FPD files available on the Wiki page if you'd like to have aluminum panels made, either the 17" panels like used in "the beast" case above, or a 19" panel for use with a 3U rack case. Double check that the design has all the mounting holes you need for fastening to your case of choice. 

Wiki page :

DXF Files :

FPD Files :

I made my own case based on the Mongbox design above, but I had to modify it quite a bit to accommodate all the modules I wanted to squeeze in.  It's currently STILL in the beta phase, but I've had several prototypes cut from wood and acrylic, and I will am close to ordering the final version.  I will make my fabrication files available when they are proven in case anyone else would like to copy my build or use it as a template.

Finally, search the forum for the latest posts about cases, enclosures, and panels if none of these suggestions fit your needs

Line Driver

The Line Driver is the module used to buffer signals sent from the MIDIBox Seq enclosure to a breakout box or auxiliary panel which typically contains the analog outputs for CV and Gate (and similar).  If your build does not require an external CV/Gate Interface, then you probably won't need the Line Driver.  It may have some uses in other custom applications, but if you are just making a sequencer with MIDI in/out, you can probably do without it. 

This module actually consists of two parts: a transmitter PCB and a receiver PCB, or Tx and Rx. Unfortunately, neither is available to order from the MIDIBox Shop nor Mike's, so you'll either have to get them fabricated or find some for sale on the Forum's Flea-market. The Tx board mounts inside the Seq enclosure and the Rx board mounts in your breakout box or aux panel.  The Line Driver allows the two to be connected using a 25-pin serial cable with length up to "5M at 1Mbit/s", maybe even longer.  Perhaps if you build the CV/Gate expansions into the same enclosure as your SeqV4, you may not need the Line Driver as the connections would be comparatively short.  Search the Forum for answers to this if you prefer to build an all-inclusive device. 

I had my Tx and Rx boards made at OSH Park as recommended on the Ucapps page.  The awkward part is that OSH Park requires you to accept and pay for three copies of any board you order.  If you have them fabricated there, you end up paying almost $50US and receive 6 PCBs.    So check the Flea-market first to see if anyone already ordered and have extras to sell, and if you end up having to order from OSH, you can offer your extras for sale there (or give/sell them to your friends when they start their OWN SeqV4 build), or you could organize a group buy on the forum.

Images that depict different hardware configurations and how to connect them are shown on the Ucapps page, but if you are building the SeqV4 and using the Line Driver Boards to add an analog expansion, you'll probably just need to see this one :

Full page :

The files you need for fabrication are available on the Ucapps page, but I've already uploaded the .BRD files and shared the project and those are linked below under "Purchase"



Order from OSH Park
Transmitter PCB
Order from OSH Park
Receiver PCB

Schematics/Images/Files/Parts List

Tx Image :

Rx Image :

Tx Schematic :

Rx Schematic :

Tx .BRD File :

Rx .BRD File :

Ucapps Parts List :

AOUT_NG Module

In order to add control voltage (or CV) outputs to the MIDIBox SeqV4, you will need to add one of the three AOUT modules (analog out). These are the AOUT, the AOUT_NG, and the AOUT_LC.  

 - AOUT provides eight 12-bit CV outputs and two gate outputs

 - AOUT_NG provides eight 12-bit CV outputs with bi-polar option

 - AOUT_LC provides two CV outputs at either 12/4-bit or both at 8-bit

For a well worded comparison and more information, see the AOUT_NG wiki page here :

I opted to build the AOUT_NG to start with, but if I find that the precision is not accurate enough for VCOs, I will switch to the AOUT module instead.  My build is not finalized, so I am still debating with myself as to whether my breakout will be a separate enclosure or a modular panel.  The AOUT_NG requires -/+12V for power, so it makes sense to build it all into a Euro-rack panel and take power from the modular PSU.  But, I my modular is too large to transport, and I have other, more portable analog synths that I could use with my SeqV4, so it also makes sense to make a breakout box that is not tied to the modular cabinet and is easy to take on location. I will update this section when I have decided and fully built my expansion.  
I've also designed and had fabricated some additional PCBs for mounting the output sockets, LEDs, and IDC headers for connecting to the AOUT_NG and DOUT (see below) boards, so there should be a very small amount of hand-wiring to do, if any, when building the output expansion. This board is designed to be compatible with the DOUT expansion layout so I can use one of the three AOUT_NG output boards as the fourth DOUT output board. 

The AOUT_NG board and a parts kit are often available at the MIDIBox Shop, and I have assembled a Mouser cart which includes all the necessary parts (correction: I have not decided how I will connect J1 to my Line Driver Receiver, so these connectors are absent until further notice).  If you don't require the bi-polar option, see the wiki page above for what parts can be removed from the order. Also, you may choose to add a set of switches instead of the shunts/jumpers if you do install the bi-polar option so you can toggle between both modes for each output.


Board and Kit :
Board only :

My Mouser Kit

Schematics/Images/Files/Parts List

Quick View Image :

Schematic :

Eagle Layout and Schematic :

Parts List

DOUT Module

The DOUT module (also referred to as DOUTX4 and DOUT_R5) is the digital output expansion for MBHP, and can be used for a variety of applications.  With a MIDIBox SeqV4, it is typically used to send gate, trigger, and clock signals to analog equipment like synthesizers and drum machines.  "Digital" in this instance means that there are two states to the signal: high and low, on and off, 5V and 0V, as examples.  The suffix "X4" indicates that there are 4 separate shift registers, each providing 8 outputs, so a single DOUT board can deliver 32 outputs. Modules may be daisy-chained to achieve up to 256 outputs if using MIOS32, or you can choose not to populate the entire board if you only require 8/16/24 outputs.  

I used individual resistors rather than the resistor array ICs. As with the AOUT_NG, I fabricated output/LED/header PCBs for my breakout box/panel so I don't have to do any point-to-point wiring.


Board and Kit

Board only

Board only

My Mouser Kit