Soundtronic MIDI Ultimate Synth

I accidently ran into this one just days ago. From what I understand it is a revamped version of late Ray Wilson’s SoundLab Ultimate, presented in EPE Magazine Feb 2019 to July 2019 and sold as a kit from Soundtronic.
There are some few vids on YT and also some more on MFOS Ultimate. A pretty powerful little d€vil. Besides one has all components soldered on one side and potentiometers and switches on the other sade, thus eliminating a lot of wiring. I like that.
Had an idea as I had some mone saved, to just get the board and then add units by units and finally the frunt panel, but as it will easier from Sountronics to get a complete kit together I simply ordered a complete kit a few minutes ago … :roll_eyes:

Til I got the kit to Sweden and got it wired up …

Soundtronics MIDI Ultimate DIY Analogue Synth Demo

Opinions on this one?! Or rather not … or well … maybe … ??


Got the kit today in a big box. Excellent work by Paul and his Soundtronics crew. Everything nicely packed with components for each module packed separately. A laser-etched panel and a pre-drilled aluminium subpanel to strengthen the vinyl.
Instructions downloaded from EPE magazine (issues 2019), though following the markings on the PCB would result in a complete synth, but having the schematics and trimming info is golden.

Some pics:


What’s the Hammond box for?

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AAARRRRRRRRGH!!! :scream: :scream: :scream: :scream: :scream:

I don’t know … :thinking:

I think I know; when looking at the final artivle about housing the synth, there’s a rectangular hole in the bottom of the (wooden) case where I guess the box will go and I think it’s meant that the PSU will go into that box.
I will assemble the PSU (tomorrow) and check. The corners of the PSU board are “rounded off” to fit the pillars inside the box.
Does that sound reasonable?!

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That actually was my guess!

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A purrfect fit.


Almost ready … almost …


Sum more build progress. Paul Cooper who adopted Ray Wilsons Soundlab Ultimate had made a great job to make a kit that is 00% user/DIY friendly. The building process follow a certain scheme that starts with the VCOs and ends with the MIDI I/F and each module can be separately tested.

This is where I stand after two days (not full days) of intensive welding:

The synth is semimodular. Instead of patch cables modules are patched through a large numbers of switches (on-off-on), where each switch picks between two sources (or non). This simplifies a lot as switching from one set-up to another is quickly done. But the downside is that some other crazy combinations cannot be made.


Had planned to install the ICs into the VCOs, but spent all day out. Maybe I will have some time left tomorrow. Else it had been tempting to continue with the next set of modules - echo, repeat generator, VCA.


The project has stalled as I spend much time trying to make the life here in Sweden endurable for a group of Ukrainian refugees. As I speak Russian it’s (too) easy to communicate and find out their needs, but I also want to show the refugees what a great place we live in.

And I am looking for an electronics engineer that can help me with my unfinished projects … :thinking:


I mailed Paul of Soundtronics with a question based on an observation.
The MIDI Ultimate is more a less Ray Wlson’s with some added units like the MIDI and that unit looks very much like any kind of MIDI to CV/trigg and it had been cool if this unit had been available as a stand-alone unit.

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Still enjoying a great time helping our Ukrainian friends. Wish my wife was here as she speaks MUCH better Russian than I do …

Anyway, I asked Paul at Soundtronics about the MIDI-module on the Ultimate as it looks very much like an add-on (Atmega with an appropriate sketch, some extra components like a DAC and CV/trigg/gate out), if there were ideas of making that module as a separate unit and this was the answer I got:

Hi Magnus,

This was something we intended to make available a long time ago, in fact we have 10 standalone MIDI2CV converters in our own synth all based on a similar design to the MIDI Ultimate. There is a newer version that appears in the M²Synth although currently only available in ready assembled version but also likely to be available in kit form later.

So yes, it will happen just no date as to when.


It’s great to see that you’re helping refugees. I know it’s frustrating to have a personal project stalled because of your other priorities. In fact I laugh when I look back to my early months of retirement when I still imagined I would at last have abundant spare time. Your posts are inspiring. Thank you.


In the case with my Ukrainian friends, being there for them gives me a lot of energy, which a successful electronics project also does.
Now a pro has made the Ultimate kit which means I should be able to have a working synth a little later.

A few thoughts out of the box - one guy in our Swedish electronics forum had built the Tsynth and was rather happy with the result. Next time maybe, and then I read about the MonoVoks4:
MonoVoks-4 in Elektor


Just booked four tickets to a theatre next month - will be fantastic!

Anyway, I have started again with the Ultimate and solder three more modules in place yesterday and checked the VCOs - the worked perfectly.
Will probably solder the LFOs and ADSRs tomorrow, but I will not push my self to hard. This is a great project and attention needed not to make any errors.

Sadly this great synth kit is unfortunate discontinued.


A photo of the not entirely finished synthesizer. Have to make a cabinet (good wood but no saw) and have to trim it.
This is a little how the machine will look like when it IS finished and the board is mounted on the panels. Here shown is the top panel loosely laid upon the board.


I am, in practice, done with the board (noticed that I have some nuts loose … for the switches) and am at the moment *struggling" with the chassis. There are good drawings of a chassis in EPE, but I have to keep it simple, due to lack of machinery.
I did pick up an off-cut of a 28 mm thick oak plank (for kitchen tops) for £2 and have cut into pieces and will do some final work to get the INs and OUTs in place. When starting this job, I didn’t really consider what to do with the PSU, so there is a slight risk that I cannot fit it into my chassis.

Left to - carve out the large hole and cut some corners.

Maybe the “planks” are to heavy, but at least the synth will stay firm on a table.


Looking good.
Oak, and maple (I’m from Québec) are my favorite woods.

I had free access tp spruce and pine at my job, but I find them to soft. Else birch, beech and oak are nice, especially birch as it can be easily tinted.
I normally use some kind of oil to get a good finish, but at this moment I have to make a long slit for the in- and output connectors and I haven’t got the very best equipment for doing this.