Yusynth Minimoog VCF

So far 2016 has been a great year for DIY modules at Lower West Side Studio.  Following the successful build of a Moogah SEM VCF I built a module that I’ve wanted since the moment I saw it; the Minimoog VCF clone produced by Yusynth.

There is nothing like the sound of a Minimoog and that is largely because of its transistor ladder filter.  Yusynth created a circuit based on the original and, like many of his other modules, he has published details on how you can create your own PCBs and build your own modules from scratch.  Unfortunately he does not sell any of his products.

Fortunately for me I didn’t have to etch my own PCB.  Synthcube.com came to my rescue by having some of these PCBs in stock!

The PCB quality was quite excellent.  Very well made and very clearly labeled.  The build documentation for the board, however, is pretty much non-existent.  Yusynth has a page on their site detailing the Bill of Materials along with some very detailed images of the board, component layout, off-board wiring and of course the schematics.  If you’re hoping for a step-by-step instruction manual though, Yusynth boards are not for you.  They are more of an intermediate to advanced build.  Yves detailed diagrams are excellent though and I had no problem putting the board together.

While the Minimoog filter is not particularly complicated there are a couple of things to note; there are six BC547 transistors required and these must be matched pairs.  In addition the four 47nF capacitors must be matched to within 1%.  To match the transistors I built a simple breadboard transistor matching circuit.  I used a circuit based on Ian Fritz’s design.

After selecting the correct pairs of transistors and group of capacitors my build went quickly and smoothly.

Once I completed the build I came to the part of DIY synth module building I dread… the panel.  Yusynth provides images for producing silkscreens of the panel, however, presently my silkscreening process is not up to snuff.  This was horrible.  I had a completed, tested working module but no panel to mount it in.

Then I discovered Free State FX.  They are builders in the US who provide panels for a number of Yusynth modules including the Minimoog Filter.  While the Canadian Dollar is very weak as of this writing the Free State FX panel was still significantly less expensive then the panels produced for me by a local screening company.  I received the panel very quickly and the quality was really good.  I should note for all those who do not wish to build their own Minimoog Filter module that Free State FX produces a built version for sale.

Mounting the board into the panel went very smoothly and it was soon connected to my modular for testing.  It works great!  I still have to run the calibration procedure to ensure it tracks volts per octave correctly.  Additionally frequency and emphasis adjustments have to be calibrated.  At this point though I’m extremely happy with the module.

One very nice feature about the Yusynth modules is that they run on 15 volts and utilize a Synthesizers.com power connector.  This makes for quick and easy installation in my modular synthesizer.  One thing I should stress is the importance of a bench power supply for testing modules before installation into the main system.  It costs a bit extra to have a power supply that only comes out for builds but in the event of a build error it can prevent your modular’s power supply and modules from being damaged.  I use a Synthesizers.com QPS2 desktop power supply for this purpose.

I’m very excited to have this module as part of my modular synthesizer.  I plan to add several more Yusynth modules to my rig in the near future!  Thanks to Yves Usson for the excellent design and to Synthcube.com for stocking the part.

UPDATE:

Here is a video demonstrating some of the filters capabilities.   These modules are now available from Lower West Side Studio.