Synthrotek is pleased to offer a complete line of eurorack synthesizer modules, power, cases and accessories in both complete units kits and panels & pcbs. 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 Dual 2164 VCA is a precision AC (audio) & DC (gate triggers or control voltage) Voltage Controlled Amplifier in 6HP.  Each channel has a linear or exponential response switch, the exponential resulting in a “poppier” response.  Adjustable output level and bleed if you want to mix in your unaffected source audio.  Butters your toast all the way to the edge.


Two identical VCA circuits

Capable of AC and DC signal processing

Linear and Exponential response select switch

CV input (1:1 input-output ratio at 5VDC CV input)

Signal Input

 CV 1 normalled to CV 2

Signal 1 normalled to Signal 2

Bleed level adjustment per channel


Current draw: V+ max 20mA, V- max 17.5mA

Width: 6HP  Depth: 3.5 cm (1.75 in)


  1. David Ellis says:

    I’ve just come across this. What if we don’t have an oscilloscope? It would be really helpful to have a rough & ready way of calibrating this and other MST modules.

  2. Steve Harmon says:

    Hi David, you can use your ears to adjust the module to taste if you don’t have a scope. It will ‘work’ even if not calibrated to our settings.

  3. Paul Geffen says:

    I built this module from PCB and I haven’t been able to get it to work. A schematic would help. Have you published one?

    – Paul Geffen

  4. Patrick Kelly says:

    Hey Paul,
    Unfortunately due to contracting and licensing issues as well as other factors, we can not release the schematic for the Dual VCA. Sorry


  5. ian rhodes says:

    Hey one of my VCA chips blew so i replaced it (on first try of the module). it might have been put in bssackwards but i replaced the chip and it still doesn’t work, the diodes looked a bit weird so i replaced those, still nothing… I live in Portland so if i walk into your storefront will you guys check it out?

  6. Steve Harmon says:

    Hey Ian,

    If you want to drop it off at the shop, we got repair forms up front and we’d be happy to try to help you out!

  7. Craig Condit says:

    I’ve just purchased and built this module… However, it generates sound (~ 50% power) when the level is fullly CW, bleed is fully CCW and no CV input is present. Is there an adjustment for this? If not, where would I need to look on the module to troubleshoot?

  8. Synthrotek says:

    Hi Craig, yes there is adjustment for this, check out the calibration guide at the end of the assembly instructions:

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