Rollz-5 Assembly Progress

The Meng Qi Rollz-5 PC board project in mid-assembly stage.
rollz-5-prewiringThe image above shows the PC board mounted behind a clear plexiglass panel that holds pots, jacks, switches, etc., sitting inside of the yellow case that will hold everything.  No panel wiring yet!   All wires will be visible behind the panel, going to the PC board.  An additional hand-built board will mount to the right and hold a voltage regulator and output mixer.  Here’s a pic of just the panel.

rollz-5-panelI’ve enhanced the PC board to provide auxiliary inputs and outputs, more panel controls, plus an output mixer, to make it into a small, self-contained synthesizer.  To the left are the eight 2-Rollz LFOs, each with two brown jacks for the nodes, an LED and an orange jack for the positive going output pulse.  Each LFO has a different, fixed rate.  Next to the right are four doubles rows of jacks and controls, consisting of 1 AVDog, 1 Ultrasound, and 1 Gong for 4 total of each module.


  • Green jack – Input pulse to trigger the envelope
  • White jack – VCA out
  • Violet jack – Aux VCA in
  • Yellow jack – Oscillator out
  • Red knob – Envelope rate
  • Blue knob – Envelope Q
  • Yellow switch – selects internal oscillator or aux input to the VCA
  • Yellow knob – Oscillator frequency


  • Green jack – In
  • White jack – Out
  • Yellow jack – Oscillator out
  • Yellow knob – Oscillator frequency


  • Green jack – Input pulse to ring the filter
  • White jack – Filter out
  • Violet jack – Aux filter in
  • Green knob – Pulse delay time
  • Red knob – Filter frequency
  • Blue knob – Filter Q

To the far right are six gray knobs.  These are the output mixer.  Each knob controls the level of two devices, for example the top knob sends the topmost AVDog to the left output and the second AVDog to the right output.  Ultrasounds and Gongs are also paired.  This is like the output mixer on Plumbutter.  Note that the outputs are independently available at full level on the white jacks for patching.  This is also similar to Plumbutter, but the Ultrasounds also have white jacks here.  Note the lack of CV inputs.  Rollz-5 is not voltage controlled (except for the internal VCA in AVDog).

rollz-5-whole-board-unwiredAbove is a pic of the mostly assembled PC board.  Chips not inserted yet.  If you look closely (click the image) you can see that the traces from the 12 outputs to the internal mixing buss have been cut.  The black/red wire to the right goes to a connector that brings in regulated 9V power.  Power starvation feature is unused. Here are more details of each section.

rollz-5-rollz-detailShows six of the eight 2-Rollz oscillators.  Jumper wires shorten the nodes to be only two, since I only care about simple LFOs with two nodes each.  Capacitors range from 0.33 uf through 4.7 uf to get the rates I wanted.  These are faster than the Rollzer from Ciat-Lonbarde.  External LED drivers will be mounted behind the panel.  I also provide a positive going output, like on the Plumbutter Rollz.

rollz-5-avdog-detailHere is one of the four AVDog circuits.  The ‘x’ resistors will be wired to the rate pot on the panel.  The 4k7 resistor seems missing, but isn’t.  I couldn’t get 1/8 watt 4k7 resistors, so 1/4 watt resistors are soldered on the back, because the leads are too big to fit the holes in the PC board.  A 100K is missing, because that is where the input to the VCA will be switched in.

rollz-5-ultrasound-detailAbove is the Ultrasound detail.  Two circuits share one 4066 CMOS chip.

rollz-5-gong-detailAbove is the Gong detail.  Two circuits here share a 4013 CMOS chip.  Trimpots will be replaced by panel pots for adjusting the filter frequency.  The aux input to the filter will mix with the pulse, just like the aux input to Gong on Plumbutter.



2 Responses to Rollz-5 Assembly Progress

  1. Sky says:

    just picked up the 2016 version. my only confusion is what kind of banana jacks did you use for this pcb?

  2. Richard says:

    Plain old Johnson banana jacks. In case you didn’t notice, these are all mounted on the plexiglass panel, not on the PC board.

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