Setonix Synth Marsupial - DIY Build

Following up our last build of the Setonix Synth Boing!, we decided it was time for another back to back build of their Setonix Synth’s newest module, Marsupial. What is it you ask? 

The Marsupial is a dual VCF module that is based around the re-issued AS3350 filter IC. Due to its normalization between the control inputs and the parallel switch, the Setonix Synth Marsupial is a unique filter that can surprise any artist when patching it up. With that being said, let’s jump into the build.

Let's Get This Build Going..

Starting off with the build of this module, we will work on the backside of the PCB first. You will want to solder the 2×5-pin power header, 3-pin Series selection header, and two 25k multi-turn trimmers.

Be careful not to hold the iron on the parts for that long as you can release or damage some of the pre-soldered SMD components.

Don’t forget to place the plastic shunt over two of the three pins of the 3-pin header–”BP” will normalize Filter A’s Bandpass output to the Series switch, while “LP” will normalize Filter A’s Lowpass output to the same.

The PCB Control Side

Flip the PCB over and begin to place all of the jacks, the mini toggle switch, two LEDs and the pots. Make sure to mount the LEDs with the short leg going through the square hole. If you mix this up, you won’t get the results you wanted. Place the panel over all of the recently mounted hardware and do not solder anything. Place a couple of the nuts on the pots and jacks to hold the panel in place as you flip the Marsupial over. Push the LEDs into their respective place and bend one leg over to hold them in place. 

Solder everything into place except for the B100k pots. These can be a little tricky and finicky and you only want to solder one left prior to checking alignment. Next double check that the shaft of the B100k pots are not touching their panel holes and if they are not, tack everything down.

** Build Note ** If the pot is touching the panel hole, just reheat the side leg you previously soldered and adjust the pot alignment accordingly. Once the pot is positioned correctly, solder the rest of the pins and the other leg in place.

Setonix Synth Boing! - Time Lapse Build

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The Completed Marsupial

Before jumping right into patching, double check your work. Look for any joints that might need to be reheated or any points that might have been missed. Once everything has been checked, plug in the module ensuring that the red strip is lined up with the -12 rail on the power header.

Test all functions: even without calibration, you should be able to get nice filter sounds from all four outputs, test all CV inputs, and adjust the Resonance from zero to self-oscillation. If everything seems to be working properly, it’s time to calibrate the module.

Marsupial Build Gallery

** Build Note ** These calibration instructions were taken directly from the Setonix Synth documentation. You can find that here

1. Power on the Marsupial and leave it powered for at least 10 minutes. Set the switch to “Parallel” mode, move “B Offset” knob to 12 O’Clock, and set Resonance knob to full CW so that each filter self-oscillates.

2. Connect a 1V/Oct source to the “1V/Oct A” input. As this is a filter and tracking is likely not critical, home studio staples such as the Arturia Keystep, MI CVPal or MFOS V/Oct Calibrator may suffice depending on your desired level of precision.

3. Monitor the “LP A” audio output with a tuner or frequency counter. Set the pitch of Filter A to a mathematically simple frequency such as 110 Hz and use the rear “A-Tune” trimmer to tune Filter A so that its frequency is roughly 880 Hz with 3V applied. This should provide a good ballpark starting point; from there monitor the frequency at other 1V intervals up to +5V and adjust the trimmer so the output frequency is as close to the corresponding multiples of the initial frequency as possible.

4. Once Filter A has been tuned satisfactorily, monitor the “LP B” output instead, making sure nothing is patched to the “1V/Oct B” input. (This will normalize the incoming CV signal to the 1V/Octave input of Filter B.) Repeat the procedure from Step 3 for Filter B.

Setonix Synth Marsupial - Final Thoughts...

The Marsupial was a quick and easy build and you will want to be careful when soldering close to any pre-soldered parts. The black panel and gold accents really make the module stand out as it pairs perfectly with its brethren, the Boing!. The module consists of 2 sides, hence the term “dual VCF”. Being that it is normalized and the IC is based off the AS3350, the filter has a unique sound that is hard to put into words. 

We know that with more time, we will be using the hell out of it and we are even thinking about picking up a second while we wait for the next eurorack module by Setonix Synth to be released. One thing is for sure, if you have been looking for a great sounding, beefy filter, the Setonix Synth Marsupial is for you. Head on over to their shop and pick one up today… make sure and tell them we sent ya too. 

If you have questions about the build process or suggestions/feedback about this article, feel free to let us know by contacting us. We look forward to hearing from you!

Until the next build …

~ f i N

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