The Kreuzung was conceived as a companion device to the
FloriVoxTron, with its case dimensions precisely matching the top of the
FloriVoxTron for seamless integration. Its primary purpose is sample playback,
but it also offers an extensive array of sound modification modules, including
a looper, modulated filtering, bit crusher, and more.
From a hardware perspective, the Kreuzung is generously
equipped. Sample playback is handled by the Robertsonics Tsunami sample player,
while effects processing is managed by three Daisy Seed Patch SM modules. The
main control unit is a Teensy 4.1 microcontroller, and the LCD interface is
powered by a Raspberry Pi Pico.
A unique challenge in this project was designing the front
panel. Departing from my usual scientific layouts, I opted for a design
inspired by orbital patterns. Although the layout remains mathematically influenced,
it features fewer straight lines, creating a more organic aesthetic. The opaque
discs on the panel illuminate in different colours to indicate their status,
and each wooden knob in a column controls the corresponding parameter.
The Kreuzung includes eight performance control panels. Each
panel is equipped with two sensors and one control: a backlit pressure sensor
that can be assigned to nearly any parameter, a chromed touch switch, and a
small knob that serves as a lag control for the pressure sensor. This
configuration provides four control points per panel, generating four
assignable signals for flexible parameter control within the Kreuzung.
Currently, I am refining the firmware for the main MCU,
focusing on communication with the LCD MCU to display parameter values
accurately. My goal is to have the final machine fully operational by mid-2026.
The Tau Hydrae and Azure Dragon have been working well in both jamming and recording situations but both have had an upgrade. There's a demo video here.
Tau Hydrae - Filter v2
The Filter v2 front panel - a much more inspiring design and controls
The old Tau Hydrae filter was the same basic design that I
used in the FloriVoxTron which
is a Elka Synthex that contained several different filter arrangements but the
reality was that I mostly used the 4 pole Low Pass filter. The reason for this
was partly down to a lack of switched level buffers whereby the level changes
between the filters was quite significant. Given the nature of the Tau Hydrae
being a live jamming synth, I thought I could do a more expressive filter.
I found the basis for a design which would make up two
filter stages using a pair of CEM 3320 filter chips. One was doing a 4-pole low
pass and the other a 4-pole high pass. Combining these two filters would make
for some interesting results and I could achieve most configurations of filter I
would want.
I was concerned about the panel space as I could only use the space that existed as I was effectively putting two filter arrangements where previously one lived. The list of possible modulation sources and configurations was quite high, so some options had to go. I managed to make it work with the only real casualty being the modulation for the resonance control. It was worth the sacrifice but I did gain a Key Follow feature.
The filter controls are straightforward: select HP mode (2
or 4 pole), adjust cutoff frequency, and toggle active/bypass. The low pass
filter has identical controls. Modulation options are below, with key follow
always active—choose half or full keyboard control voltage. Key follow
naturally adjusts cutoff frequency as you play across the keyboard.
The result is not perfect as I think the resonance for the
high pass needs some work. It could be schematic design or a setting of which I
don't know now. I can say that it is more interesting for creating sounds.
Azure Dragon - Spring Reverb v2
All the modules on the Azure Dragon are wonderful except for the Spring Reverb. It was noisy and low level. The tone controls didn't really work and the feedback section was a waste of time. It was rushed. I wanted something more inspirational.
The new Spring v2 - the controls remain the same as v1
I regularly source designs and boards from Australian audio guru Rod Elliot. He has several spring reverb schematic designs but the one I chose was the Spring Reverb for Guitar or Keyboard. His article made me understand where the original design was flawed. I needed a new reverb tank which was no biggie and I could get one with the same dimensions as the original. His design didn't include any tone controls so I took a 3 band eq design out Douglas Self's Small Signal Audio Design which suited the spring reverb perfectly. Now I have a clean and high responsive spring reverb that I see moving which allows for a great swang!
One of the nice performance features of the FloriVoxTron is the four separate layers / voices that can be switched in and out at any time. I've often used this feature by a setting a drone sound on one voice, placing it in hold and then selecting another voice to play as a melodic layer. The only problem with this function is not a limitation of the FloriVoxTron's but my limitation of only having two arms. Hence, I decided that a foot pedal that turned the four voices off and on was a necessity.
FloriVoxTron MIDI foot pedal
As you can see it's pretty straight forward. It connects to the FloriVoxTron via MIDI. In affect it is just a MIDI controller outputting the assigned MIDI controller messages to turn the four voices off and on. It also has a MIDI input so the keyboard can be controlled externally via another keyboard or from a computer. It's powered via the USB-B connection.
You might also notice that the buttons are set at two different heights. This is "designed" so it's easier to feel them under your feet without looking. I say "designed" because it was actually a design mistake inside the case. When the buttons are mounted flush they take up quite a large amount of room inside the case. This was space needed by the PCB. It turned out to be a good result.
The Azure Dragon is an effects rack which was designed with the primary purpose of being a flexible and mostly analogue effects rack for my Tau Hydrae monophonic analogue synthesizer.
The video presentation which goes through each module with sound demonstrations can be seen here - Azure Dragon Effects Rack
One of the several DIY instruments used by myself as Amongst Myselves - www.amongstmyselves.com
The Effects
One of the technical aims of the unit was to use as many classic analogue effects as possible. The Azure Dragon contains the following modules:-
Valve Overdrive - this is the "classic" Matsumin Valve Caster design which is a low voltage overdrive including a pair of switchable clipping diodes.
Auto Panner - an Arduino based LFO module controls a SSM2164 stereo VCA
Spring Reverb - a real tank reverb, Accutronics, with a basic driver module which includes feedback and basic tone controls
Feedback Mixer - this allows any module to be hooked up to feedback its own signal. It includes a parametric EQ for tuning the feedback sound
In addition to these effects modules there are input and output modules which interface to the real world and include LED level meters and level controls. All the effects are connected via 3.5mm patch cables at the bottom of the unit. The output module has balanced outputs.
Given that the primary purpose for the Azure Dragon is to pair with the Tay Hydrae, the patch bay includes connections to the Tau Hydrae various control outputs like the Keyboard Pitch and Trigger signals along with the LFOs. Several of the effects modules have been made to utilise these control signals.
The Case
The case has been designed to both match and mount to the Tau Hydrae. It's made from 12 and 16mm MDF which has been painted satin white acrylic paint. The front panel was cut with my CNC router in two sections due to the router's limited cutting area. The wood pieces are held together with wood glue and positioned with biscuits placed with a biscuit joiner. The unit sits on the hardwood side panels of the Tau Hydrae and is fastened with two aluminium straps to the front.
The case does have a cooling fan as I was concerned that the valve along with several linear regulators would get a little warm without ventilation. I could remove the fan and just have vents but this can't be decided until I have used the unit a little.
All the boards for the different modules are mounted to the rear panel.
The Power Supply
The power supply is a standard design of many of my projects. This is essentially the same as the MFOS - Adjustable LM317/LM337 1.5A Supply which is a transformer based +/- 15v rails. 5v is derived inside the Azure Dragon with linear regulators for two modules that require it.
It was intentionally designed to supply more than twice the amount of current needed so the unit stays cool and the components last a long time.
Like the main case, it's made from 16mm MDF with CNC routed acrylic pieces for the connection mounts and the side vents.
The transformer is a toroidal type which has a maximum of +1.5A per winding but as mentioned earlier, the Azure Dragon needs much less, running in at around 700mA on the positive rail and about 400mA on the negative.
The Panels
A method that has become standard for my designs is to use CNC (Computer Numerical Control) routed 3mm acrylic. The markings are engraved using a 0.5mm bit which is then filled with acrylic paint. Left to dry and then cleaned up with a light abrasive kitchen cleaner. Finally sprayed three times with a satin clear spray. This is the best process I have come up with that is relatively easy and cheap to get a great looking and reasonably durable result. If you don't consider the purchase of the CNC, computer and many years of trial and error.
I still use an old 2D design program called Freehand. It is quick and does everything I need. In an ideal world it would be nice to have 3D capability as I do have to take three dimensions into consideration. I have come into issues in the past but a combination of learning something new along with the simplicity of Freehand stops me doing this.
I have dabbled with OpenSCAD but only in 2D. This was very useful when doing large front panels like my Expanse project where I was able to mathematically modify sizes to make modules fit together. This could then be brought into Freehand to replace positional objects with final cutting objects.
The Modules
I thought I'd share some issues I had making the various modules.
The Chorus was the most difficult module. I purchased the PCB (printed circuit board) along with the Phaser PCB from Serge. They've taken the old stock from Jürgen Haible's estate. That was the first challenge as they're limited in numbers. The second challenge was where do I get TDA1022 BBD chips from? Thankfully a good friend has lots of them due to his hoarding nature and stripping down old organs for these, now valuable, components. I needed to find those components before I ordered the PCBs. As far as the construction of these modules, I had Jürgen's notes which are archived thanks to Serge and also Bill and Will's construction notes.
The Chorus gave me grief because I had a bad batch of TL072 chips. These are used to create the LFOs. I just wasn't getting a deep enough chorus effect which I struggled with for quite a while. I thought at first it was the CD4011 chips which I replaced with three other brands of chip I borrowed. I got there in the end.
The Phasor was pretty straight forward although I had to go beyond my usual component supplier, Tayda Electronics, to get some of the better quality capacitors.
The Oakley ADR30 was a dream to build up. No issues with this build. Though getting a BBD design that looked like it would do the job took a false start. I had previously been trying out another delay design which was a guitar pedal. This was not great quality which led me to looking into Tony Allgood's work. Alas, the BBD chips I had purchased from Cabintech were not the correct ones, so this led to another expensive purchase from the other side of the world. Oh well.
The change I made to the ADR30 was to attach a more flexible LFO. I have designed several Arduino and other MCU based LFO modules in the past. This design uses a Pro Mini Arduino which controls a digital potentiometer which I use as a voltage divider that is then fed to a buffer and bias amp to output the required 6v Peak to Peak LFO signal.
The Spring Reverb driver was another small issue for me. I'm no electronics engineer and my understanding of these things is enough to put things together but to actually design something like a spring reverb driver wasn't going to happen fast. I did find a few designs which I had tried but I wanted some tone control. What I found was a driver with a basic Bass and Treble tone control and Feedback which I have used but I am not 100% happy with it and I do have a new design ready to install. Watch this space.
The Feedback Mixer was my design with other peoples worked tacked in. I stole the parametric EQ design from Rod Elliot. He's someone who knows audio and I have used his designs and purchased PCBs when appropriate for the project. I have purchased a batch of his balance transmitter and receiver PCBs with one being used as the output stage of the Azure Dragon. The Feedback Mixer allows the output to be fed back into the input of an effect. The parametric EQ allows this feedback tone to be tuned.
The Auto Panner uses previously designed PCBs. Firstly, the LFO board is a cut down version of my TMNSD PCB. Although it's not designed as a LFO, what it does have is a high resolution DAC output, easy access to many Arduino I/O connections and some basic buffered outputs. This is an Arduino based board which controls a dual 12 bit DAC (digital to analogue converter) which in turn outputs a 0 to 10v signal. This signal is then fed into the other previous design, dual V2164 based, VCA module. The code running on the ADR30 is very similar to this code.
LFO Design
The original design for an LFO module came with the FloriVoxTron a few years back. This unit has many LFOs and using a MCU to create them seemed like a no brainer. It would be able to create any number of waveforms and do things that I am not sure an analogue LFO could do. The Expanse has a Quadrature LFO which has a Direction mode LFO built into it. This is a Square Wave LFO which changed the direction of the main LFO waveform, a very nice effect. By the way, a quadrature LFO has four outputs for the waveform which are 90 degrees out of phase to the previous output. Once again a nice effect when applied to multiple VCFs and Wave folders.
The LFO design has changed over the years. They generally have about 10 waveforms in total but are often reduced based on the LFO purpose. For example the LFO for the Auto Panner didn't really need to have both a Sine and Triangle waveform due to the less obvious nature of the effect being panning.
The two LFO designs in the Azure Dragon have a useful feature which is a single trigger function. I've not tried this in the field (jamming), but it takes a trigger input signal which will cause the LFO to only output one cycle of the chosen waveform.
The construction bug has never left me and I wanted to build a more versatile mono synth for live jamming situations such as those with my band, DFTM. I had made the Therematron a few years back but this doesn't have a keyboard. Having no keyboard that can directly control the Therematron makes setup and gear transport complicated. Thomas Henry's synth designs also caught my eye so I set out to make a more complex mono synth.
Over the past few years I had collected the schematic designs of Thomas Henry, well known in the synth DIY realm. In particular his "An Analog Synthesizer for the 21st Century". What attracted me was his unconventional use of non-synth parts to create synthesizer modules. From these initial schematics came the design for the Tau Hydrae. The layout is a stock standard subtractive synthesizer signal flow but with some special features to make the exploration of sound creation more flexible.
Thomas's designs are aimed at modular synthesis so I needed to think about routing within this new build. My initial design of the Tau Hydrae had a 1/8" jack patch panel for all the modulation input selections but I harkened back to my old Roland SH-5 and I realized I wanted something that was a bit easier to setup than a patch bay with the result being lots of switches. The patch bay would have made this unit quite a bit larger and it's already quite big and heavy at 900mm wide.
I mentioned that this is a monophonic synthesizer but this isn't strictly true. Due to a hardware choice I have two 12 bit DACs on the MIDI to CV converter which might as well be used. The Tau Hydrae has all the hardware in place for duophonic to work where LM-VCO is one voice and the XR-VCO is the other but I have not implemented this in the software.
One of the aims for this project was less wiring. Wiring is my most hated part of any project so I started out with the idea of having a bus which contained almost all modulation and audio data on a ribbon cable. In all but a few places, the ribbon cable and power is all that connects between the modules which I consider a great result.
Before you read on, you can always watch the video I've made describing the modules with small demonstrations of the features - Tau Hydrae
Module Design
With the reduction in wiring in mind, the modules are made up on two printed circuit boards. One board contains mostly the front panel controls and the other board is the main part of the modules functionality. Some of the PCB designs I used are designed by other synth builders. This made the front panel boards a little more difficult to design as connections were not located in the idea places but the time it would have taken to redesign the main boards would have been longer. So I managed to get around these issues.
Where I had to design a totally new board, I had the flexibility to design the main board and the front panel board at the same time to position components in more appropriate locations to avoid clashes with hardware controls like switches and potentiometers.
I have to admit that I could have placed the bus connections in more appropriate locations should I have thought of the boards locations within the front panel. In all cases, the bus connector is located on the front panel PCBs which means they are slightly obscured by the front panel itself.
The choice of knobs was really down to what I could find that had a larger and smaller variety. Having the two sizes helps break up the sea of knobs and switches. Most of my parts come from Tayda Electronics and I had purchased these knobs a while back with the idea of using them on the Expanse project. I wanted to have a larger knob which took control on the mostly used control within a module though in many cases I sadly suspect ascetics overrode practicality.
The Case
I set out for the case to be similar in style to the Yamaha CS range of the late 70's. In particular the CS-15D which was my first synthesizer I got when I was a teenager. This particular CS15D was never the same again after I opened it up and adjust too many trim pots. I also wanted the design to match the John Bowen Solaris to some degree, as this is the other synth I use for jamming, which is why I went for a white case with the wooden end pieces. Always wanting to try different approaches to case design, this unit has a piano hinge on the rear for access to the inside of the case. This is a pretty common approach with manufactured synthesizers. The original planning of this worried me as the case is mostly made from MDF and as many will know MDF isn't the strongest when it comes to screwing into, but it seems to have worked.
The front panel is also made from MDF which I have cut holes for the modules to sit in. This was done on my CNC router. The wood piece is too large for a single pass on the machine but I could simply move the piece along the cutting area and start the second cut as the accuracy could be out by a millimeter or two without issue. The mounting of the modules was originally designed to be screw inserts. This would allow the modules to be removed for whatever reason quite easily. Alas, MDF doesn't really like being countersunk and when I tested the screw inserts, the wood starts to peel apart and go fluffy. Adding to this was trying to paint said fluffy wood led me to use nuts and bolts to hold them to the panels.
Front panel has been CNC routed - note mistake on the left hand side - the wonders of Spak Filla
Having followed woodworker and painter Peter Millard on YouTube for some time, I learnt that I could probably get a decent roller finish on MDF. It worked quite well though I could have done a better job at filling gaps before painting. Sorry Peter.
The side pieces of wood are varnished Tasmanian Oak. This is a nice hard wood that is sustainable in Australia. The symbols I have engraved on the sides are the hydra symbol from Greek mythology. Tau Hydrae actually being a star of the Hydra or water snake constellation.
Module Panels
I tried a new technique for these panels which I am not 100% happy with but it's an improvement on my previous method.
For many of my projects I use my CNC router to cut all the markings into 3mm acrylic. I then clean all the excess acrylic swarf off and fill the engravings with white acrylic paint. After this has dried, I use a mild abrasive cleaning paste to remove the excess acrylic paint and there we have a nicely filled front panel.
The issue I've had with acrylic is that glossy acrylic shows up grease from hands quite quickly. For this project I took a slightly different approach. Previously I would roughen the surface to take the shine off the acrylic as it helps mask grease and other marks. I continued to use this approach but using a heavier scourer to give quite a matt finish but being careful not to scratch the acrylic too much as the acrylic paint used to fill the engraving would start to fill those scratches.
My first complete panel - very happy man
Once I had done the acrylic clean up, I sprayed the panel with three coats of satin clear spray. What this has done is provide a slightly more durable and polished finish compared to a burnished only panel. I still have to be careful when tightening up screws on the pots and switches though. I think it might be my penultimate approach for future projects. I can't see how I could improve the technique without going to a metal panel which would have to be manufactured by someone else. There goes DIY out the window.
By the way, the colour scheme was inspired by the East German synth, the Subharchord which was orange and blue and I was looking for something a little less scientific looking that most of my designs follow. The wonderful Hainback does a great demonstration here -
Here's a breakdown of all the modules
Again if you want to see these modules with a short description and demo go here -->> Tau Hydrae
Main MCU
1. Arduino Mega 2560 MCU - I chose the larger Arduino so I could have two hardware serial ports in the form of MIDI interfaces
2. Reads in the Arp panels switches
3. Runs the Arpeggiator
4. MIDI to CV converter for the two VCOs
5. Analogue Portamento
6. Output interface - sends for both CVs, Trigger, Gate and both LFO outputs
7. Deals with various Arp Clock inputs
8. Transpose function for Arp
9. Arp idea based on Sh-101 - my second synthesizer
LFO A and B - Thomas Henry design
1. Wonderful module with combination of Delay, Lag, and VCA which gives you a delayed vibrato for example
2. Slightly complex input triggering setup
3. Custom square wave output with pulse width control
4. Voltage controlled speeds from various sources - LFO-B, ENV-A, S&H and Bender
5. LFO-B can be controlled from LFO-A, ENV-B, S&H and Keyboard CV
LM-VCO - Thomas Henry design
1. Uses a LM13700 as an oscillator which is usually used with VCAs and VCFs
2. Fixed or Keyboard voltage controlled
3. Coarse and Fine Pitch Control - large knob controls the Coarse Frequency
4. Lin Modulation input - AC / DC filtering - LFO-A, ENV-B, S&H and Bender
5. Waveforms - Sawtooth, Triangle and Sine but also Square via the Wave Wiper or a mix of those first three and square - maybe show a oscilloscope screen grab of a mix
6. PWM via a knob and LFO-B or ENV-A as source
7. Exponential Modulation - LFO-B, ENV-A, S&H and XR-VCO
8. Wave Wiper Modulation - LFO-B, ENV-A, S&H, and XR-VCO
9. Octave switch
XR-VCO - Thomas Henry design - Mostly the same as LM-VCO
1. Uses a XR-2206 function generator chip as the oscillator
2. Instead of PWM we have SKEW which bends the shape of the selected waveform
3. Sine and Triangle waveform options but they become sawtooth pretty quickly
Noise - Thomas Henry design
1. Digital noise generator - gives interesting sound on the lower end - quite digital
2. Keyboard Tracking control source
3. Modulation - LFO-A, LFO-B, ENV-A, ENV-B, S&H and Bender
4. Linear or Exponential Modulation input selector
Filter - Elka Synthex copy by Xnotox
1. As used in my FloriVoxTron
2. AS3320 filter chip
3. Two separate Frequency modulation inputs - one has LFO-A, ENV-A with AC/DC filtering with the other having LFO-B, Bender, ENV-B and S&H
4. Resonance with modulation control - LFO-A, LFO-B, S&H, ENV-B
5. Small caveat is a doubling of signal level when using the LP24 filter type
6. Voltage controlled Resonance
ADSR A and B - Thomas Henry design
1. Standard ADSR setup with Short or Long timer switch
2. Inverted signal output
3. Extra - looping ADSR function - retriggers when the envelope returns to 0v
4. Built in LFO for triggering the ADSR
5. A little complicated as you have to select whether it's in Trigger or Gate mode
6. Can be triggered from the Keyboard Trigger, Gate, LFO-A or LFO-B
Sample and Hold - Thomas Henry design
1. Addition of a comparator on the Trigger input to allow for any signal to trigger the S&H
2. Uses a MCU to create the internal clock sampling signal which also doubles as a divider or multiplier when in external triggering mode
5. Also has a Lag control to smooth out the sampling
Sub Oscillator - Shed Synth Design
1. Has some great artefacts should it get some unusual waveform inputs
2. Source for tracking is LM-VCO or XR-VCO
3. Output level controls for -1 octave and -2 octave
4. Filter control to smooth out the square wave output
Mixer - my own design plus Moritz Klein additions
1. Basic virtual earth mixer for mixing - LM-VCO, XR-VCO, Sub Osc and Noise
2. 440hz tone generator for tuning
3. Moritz Klein overdrive section
4. Blend control to mix the overdrive with the original plus an invert for the original input - interesting results
5. Overall output level control
Amp - Mark Irwin Design
1. AS2164 VCA
2. Two independent modulation input options - one with LFO-A, LFO-B, ENV-A and LM-VCO
3. One input has the addition of a AC/DC filter
4. Second Modulation input has S&H and Bender as an input option
5. The VCA can be run in Linear or Exponential mode
Keyboard
1. Original planned to be a salvaged key bed but decided on a new controller purchase where I used the controllers MCU to interface to this project. This was a Roland A-49 controller keyboard.
Control Panel
1. Volume control - where the output can be muted while the rear accessed headphones is still active - independent level control as well
2. Bender - this outputs a CV on the bender
3. Modulation - both LFOs are fed through here via another LM13700 VCA where two switches control whether the outputs of the LFOs are affected by the modulation control
4. Arp Speed control which doubles as a MIDI CLOCK divider/multiplier when the MIDI clock source is used for the arpeggiator
5. Portamento - this is applied to both control voltages at the same time.
External Control
1. MIDI input - accepts MIDI note data on the input
2. MIDI output - sends out polyphonic MIDI note data along with velocity information allowing more control over an external keyboard
3. The internal keyboard can be isolated from the synth allowing only external control of the synth but also allowing the keyboard to control and external synth
4. CV-A and CV-B control voltage outputs on the rear along with Trigger and Gate signals
5. LFO-A and LFO-B are also output which is planned as a control source for the Azure Dragon effects rack
6. Sustain pedal connection - which is not implemented as yet
7. Two audio outputs - not stereo but two independent mono balanced outputs
8. Headphone output and level control - headphone amp is a Rod Elliot Electronics Project
I had been thinking about a noise box for some time but I wanted more than a simple MFOS Noise Toaster, as good as it is. I had a case in mind but it was a little large for just the Noise Toaster. Then I remembered that I had a MFOS Echo Rockit floating around.
The Echo Rockit is a delay unit based around the PT2399 chip. It's lo-fi. It contains the delay unit along with a VCF and modulation controls. The Echo Rockit module I originally got to be part of the Therematron but I was not happy with the quality of the unit. That said I'd probably enjoy the lo-fi aspects of it now.
I have several of these old wooden cases which came from a haul at an old college. They were part of a physics department and they're all old electronic experiments. Nicely made cases that wouldn't go to waste.
I had some fun with this design. I renamed all the controls and adding in some aliens and some lighting effects as you do.
Power is always a necessary and challenging part of a design and these two units have slightly different requirements. Given that it's a stand alone type instrument, I felt it would be better with batteries. I'm not a fan of single use batteries and I do have a large stock of salvages 18650 LiPo batteries. What I came up with was four of them in series and a voltage regulator. LiPo batteries prefer not to be drained to totally flat so I have included a simple circuit which will light a LED when the voltage become a little too low.
Here's a video I did for a friends birthday. Weird present.
The Music From Outer Space web site is now hosted by SynthCube since Ray Wilson's death. They have also continued to supply all the PCB and kits that Ray had.
Rear of the unit where you can see the MDF extension to deepen the case.
Another small project. This time we have a controller that attaches to my audio interface. The interface in question is the RME Fireface 400. A wonderful interface. The front panel which is close by, has only one control on it which is a rotary encoder that allows you to access most of the controls but it is not easy. I wanted a controller which did some basic things - control the speakers level, switch over to the headphone output, dim the audio level and do a mono mix.
This project had some new challenges. The Arduino I have used is the Pro Micro. This is a newer type of Arduino which has the nice feature of a Atmega 32u4 as its USB interface which allows us to use the Arduino as a MIDI device. This avoids the extra hardware for traditional MIDI connection at the computer end and the controller end. The USB also powers the unit. Nice simple single connector for MIDI and power.
The wooden knob is a nice feature and the nice thing about jarrah is its strength.
I wanted to try making a sloped case as well and including my recent(ish) haul of old jarrah floorboards. I got a pile of old floorboards from my father-in-law which were unprocessed. So, I came up with a method of using my CNC router to finish the wood so it could be used for such projects. This takes some time and is a little wasteful but the wood would have been trashed otherwise.
The electronics is quite simple. The switches are individually attached to inputs on the Arduino along with the orange LED and rotary encoder. I've used an USB extender cable which gives us a USB-B socket on the rear of the case. The Pro Micro board's micro USB connector is notorious for coming off!
The software was a little confusing. Like many computer audio interfaces which have MIDI control, there are a few different methods of communication. The one I chose does quite have the options that I have included on the controller. For example the Speaker and Headphones switches are the same code. They're a toggle with the MIDI code instead of a OFF / ON option. It works ok.
Like most of my projects, this has been made to solve a problem. My studio's MIDI instruments are on one MIDI buss which is made possible by my UM43 8 channel MIDI merger (Link to come). This makes it possible for me to control any synthesizer from any keyboard as long as I can change the MIDI transmit channel separately from that synthesizers MIDI receive channel. This is often not the case or not easy to do.
The UM44 MIDI Channel Changer came from an earlier and more complex design, the MIDI Warper. This unit took MIDI input data and allowed the user to change the destination MIDI channel for note data, modulation wheel, pitch bender, Sustain pedal and expression pedal. This was connected to the Solaris as changing these parameters on the Solaris was not easy to access.
Although the design of the MIDI Warper allowed for several MIDI controllers channel to be changed, it became over complex for its use. I never changed any of those controllers and only changed the channel.
Rear view
The UM44 is much simpler. It only changes the MIDI channel of all incoming MIDI data. Instead of having a complex rotary encoder and LCD, it has 16 buttons with associated LED. Quick and easy to use.
The hardware of the MIDI Changer is simple from my perspective. It has a Arduino Pro Mini as the MCU connected to a MIDI interface. Unlike the MIDI Warper which has a LiPo battery and all associated charging and step converters, this is powered externally via a USB-B connector. There are two PCBs in this design. One contains most of the electronics and the other the buttons and LEDs.
A slightly more complex part is the reading of the buttons which is done with a slightly dodgy approach of a large resistor ladder read in via an analogue input. When you press a button it picks off the voltage across the large arrange of resistors across the buttons. If you press more than one button at a time you get a false reading. This seemed a reasonable approach given any other approach using a analogue or digital multiplexor would have made it overly complicated.
The LEDs are controlled in a matrix fashion with a 74HC595 8 bit shift register. 4 bits of the 595 control the cathodes of the 4 columns and the other 4 bits control the anodes on the rows.
The case is made from offcuts of stuff I had laying around. I used two pieces of jarrah hardwood to make the majority of the case. The lid and base are 3mm acrylic along with the rear piece. Yet again playing with design to make the case easier to cut and piece together. All routed with my CNC router.
I have made two of these so far. One for the Solaris and the other for my new Tau Hydrae mono synth.
An Abandoned Day has now been released. Thanks to the support so far from fans, radio programs and reviewers. There a two notable reviews out so far from Michael Foster @ Ambient Visions and Bert Strolenberg @ Sonic Immersion
The CDs are back from the manufacturer, a big thank you to Replicat for their high quality service. The international radio copies are on their way as are the reviewer copies. The website is almost ready. The big day is the 1st of December though the my two stores (here and bandcamp) will be opening earlier, so keep an eye on them.
The CDs are back from the manufacturer, a big thank you to