The Serge Dual Universal Slope Generator is a legend in modular synthesis.  It is the basis of most voltage controlled slew modules, including Make Noise Maths.  I have built a pair of Ken Stone’s Serge VCS in MOTM format and also Ken’s DUSG in my pseudo BugBrand format.  Earlier I had built a pair of MOTM-820 with Oakley OMS-820 to imitate the DUSG.  It is a legend, because it is able to perform a multitude of different functions, from VCO, LFO and Envelope Generator to Lag Processor and Pulse Divider.

In Eurorack I have a pair of Steady State Fate Mini Slew modules.  But I wanted to add yet another DUSG that I could use in a different Eurorack case.  I decided on the Random*Source DUSG, available as a DIY kit from Thonk.  The kit contains all parts needed and comes with surface-mounted components already soldered onto the boards.  It is a relatively easy build.

Features

The Random*Source Serge DUSG has panel features similar to the Catgirl Synth Serge Voltage Controlled Slope, but doubled.  But there are a few differences.  R*S DUSG substitutes a Pulse out on one side in place of the Bipolar output.  Maybe they should have called this Square, because that’s what it is.  A useful addition.  Secondly, the switch that controls the response curve for the CV inputs is three-position with a center off.  Center off disconnects the feedback from the output to the CV input completely, which is handy to get the linear slope.  The two positions allow selecting logarithmic or exponential responses that without an CV patched in allow the CV attenuverters to modify the curve of the slope.  The manual doesn’t have details on this curve feature, but I’m planning to investigate it farther and compare to the VCS.

Panel Design

The panel is a Eurorack style, using Davies knobs like Serge.  The graphic around the CV attenuverters resembles classic Serge.  Random*Source supplies a red LED for the left and a yellow for the right.  A trimpot lets you adjust the brightness of these LEDS and I set it to maximum.  The LED can indicate only a positive voltage, which is normal when oscillating or making envelopes, although the outputs can track negative when following an external input.

The jacks-on-top design is perfect for my application (see below).

I don’t understand the color coding around the jacks.  I’m not sure about the Serge banana jack color coding scheme, either.  Serge tended to use Red for pulse type inputs and outputs, and Black and Blue for other inputs and outputs kind of willy-nilly.  R*S chose a surround color for the mini-jacks that somewhat resembles this, at least in the use of Red for Trig in, End and Pulse out.  The CV inputs are all white, but so is the main output.  The inputs and bi-polar output are Black.  If the main outs were Black it would seem more consistent to me.

Construction Photos

Pictured above is the back and top sides of the smaller PC board, the one that holds most of the circuitry.  Power header and trimpots are on the back.  After assembly to the panel board the top side of this board is inside.  Electrical connections between the two boards are routed via eight header pairs, with the male pins on the component board and the female sockets on the panel board.

Pictured above is the back side of the panel board, showing the female headers.  Panel pots, switches, jacks, and LEDs are soldered to the opposite side of this board.  The lower photo shows the two boards together.  Below is another perspective on the final assembly.

All panel parts are inserted into the PC board, but not soldered until the panel is affixed over them and all parts have been tightened down to the panel.  The spacing between the panel and board seems just about perfect.

Mystery Header

The back of the panel board has a header position, unfilled, with what looks like two jumper options, labelled S and E.  There’s nothing about this in the construction manual.  I wonder what it’s for.  I kind of regret not soldering in header pins, so I could try it out.  Now I’d have to remove the panel for access to solder.

In the Box

Here’s where I put the DUSG.  It works nicely in this case, which has controllers mostly below and audio processing above.  The jacks-on-top design fits right into my plan.