Synthrotek is pleased to offer a complete line of eurorack synthesizer modules, power, cases and accessories in both complete units and kits. We now offer a very complete analog modular monophonic voice with many accompanying utility modules. This new complete voice is the product of a collaboration with synth guru George Mattson, who now joins us in releasing our new MST (Mattson – Synthrotek) line of premium modules.



The MST VCO is a 100% analog 6-octave 1V/O trackable precision oscillator with full pulse width and modulation controls and with 5 waveform outputs.


  • Coarse and Fine tuning controls
  • Manual and CV controlled PWM (pulse width modulation)
  • 3-octave selector switch
  • Temperature compensated
  • 2 Modulation inputs; MOD1 can be attenuated with MOD 1 AMT knob
  • Pulse Width Modulation input which can be attenuated
  • 1V/O adjustment trimmer for making adjustments
  • 1V/O CV input jack
  • 5 waveform outputs (can be used simultaneously): Sine, Triangle, Sawtooth, Sawtooth +1 octave, Square
  • Frequency range: 2Hz-14.39 Khz (Sawtooth +1: 28.77 Khz)


  • Current draw: 45.9mA on +12V; 46.3mA on -12V
  • Width: 10HP
  • Module depth: 1 7/16 inches (3.7 cm)



  1. JT St James says:

    Looks interesting. Any ideas on a release date?

  2. Steve Harmon says:

    We are still finalizing the last round of prototypes, hopefully out in less than 2 months.

  3. geecen says:

    Hi there,

    I was wondering whether this will have linear fm or just exp fm?


  4. Patrick Kelly says:


    The FM on the VCO is going to be Exponential.


  5. Ken says:

    Any news on the release date?

    Looks really interesting!

  6. Patrick Kelly says:


    They Will be available for sale starting 8/27

  7. Ken says:

    @Patrick Kelly
    Thanks for the quick reply!

    I’ll definitely order at least one

  8. David Yim says:

    Is the schematic provided when you purchase the pcb? If not, how do expect the customer to trouble-shoot the circuit?

  9. Steve Harmon says:

    Hey David,

    Due to the licensing agreement with our designer, we are not able to produce a schematic of the circuit. If a customer needs assistance troubleshooting, we are available through phone or email to help in any way we can. We also offer repair services for customer built kits.


  10. David Yim says:

    Thanks for the quick response. I’m in the middle of a couple of other builds right now, but I plan on getting some Synthrotek PCB/panel sets in the near future.

  11. Sebastian says:

    Hi! It’s possible to replace resistor like 49.9k to 50k, 1.58k to 1.6k, 2.37k to 2.4k etc etc..? This king of value is hard to find!


  12. Steve Harmon says:

    Hey Sebastian,

    The resistors you are looking to replace need be as to close to those values as possible. They are 1% resistors, meaning they are very precise compared to the 5% resistors you typically see. I would definitely suggest you use the correct values listed in the BOM.

    Good luck!

  13. Grzegorz says:

    Hi, I made this module, but unfortunately it did not work 🙁
    After connecting the power supply has no sound. Can not be calibrated.
    Only on “tri” output signal is about 330 kHz. (if the jumper is on)
    Can You help? 🙁


  14. Steve Harmon says:

    Hello Grzegorz,

    From what you are explaining you could be having 1 of a few different troubles. We have a troubleshooting guide that you should check over here. Please go over all of the following information, and if you are still having trouble we also offer to have kits sent in for 1 half hour of free troubleshooting/repair at our shop.

    From what you are explaining, you could be having an issue with diodes or may have incorrectly installed a resistor. Please check against the bill of materials and make sure all the resistors are correctly placed.

    We made a resistor chart you can find here to confirm the color codes of each resistor which will help you confirm all of them are correctly placed.

    You may also want to go over for any cold solder joints as that may be part of the problem. Quick touch ups on your board could resolve the issue.

    Also check diodes and make sure they are working. If you have a multimeter this tutorial is really helpful.

    Let me know how this helps you out, and if you still need help let me know. I’d also suggest emailing us at If you do write us back please copy and paste this conversation in the email so I know where we left off.

    Best of luck and let me know how it works out!


  15. alex says:


    I have built this module from pcb/panels and it is, or, seems to be, working correct, however i have a concern. is it normal with this oscillator for the output volume to decrease as the pitch increases? I am quite new to synthesizers and eurorack, but i do not notice this behavior from my MS-20.

  16. Steve Harmon says:

    Hi Alex, this does not sound right, apparent volume usually goes up with frequency. I have not noticed this before.

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