Rollz-5 Schematics

rollz-5-pcb-frontThis is the Rollz-5+ PC Board by Meng Qi.  The circuits follow fairly closely the original paper circuits, designed by Peter Blasser.  I am building it with modifications of my own to make it more modular.   Here’s the back side of the board.

rollz-5-pcb-backI’ve drawn schematic diagrams for all of the circuits and added my own modifications to the drawings.  The Rollz-5 circuits are early, non-voltage-controlled versions of the ones that ended up in the Plumbutter.  While Plumbutter schematics are available (see previous link), I haven’t been able to find normal schematic diagrams for the Rollz-5.  Peter B. provided the paper circuits only, which are pictorial graphics of the circuit layouts.  I drew my schematics referencing those graphics and checking against the Meng Qi board shown here and against the Plumbutter schematics.  (There may be mistakes on my diagrams, so be warned.)


rollz-5-avdogAVDog is made up of three internal ‘modules’.  An envelope generator, made from a filter set to a very low frequency, drives a transistor VCA that gates a simple audio oscillator.  ‘Inpulse’ triggers the envelope.  I’ve added four features.  A dual-ganged pot replaces the ‘x’ resistors, so you can control the period of the envelope.  The oscillator has a separate output jack, plus a switch into the VCA so you can cut it off.  Finally I added an auxiliary input to the VCA.

Also show is one of the 3-Roll Rollz circuits (which is unrelated to the AVDog).


rollz-5-2-roll-lfoI bread-boarded up the Roll circuit and played around with it.  I made 2-, 3-, 4-, and 5-roll versions.  I found that the odd number ones oscillated at ultrasonic frequencies (~100 KHz), and I didn’t want those.  I found that a 2-roll produced a nice LFO.  I added a positive pulse output (like Plumbutter) and an LED driver by Ken Stone.  The two ‘nodes’ still have jacks.  I’m building all eight Rollz identically, but with different value capacitors.  These are the rhythm generators.


rollz-5-gongGong is a low-pass filter, combined with a circuit to ring it.  Interestingly, this gong circuit is different from both the paper gong and the gong in Plumbutter.  The PC board has places for two 2M trim pots, but I will use a ganged panel pot, so that you can adjust the filter frequency.  I’ve also added an auxiliary input, so you can patch any of the other modules through it.


rollz-5-x4-ultrasoundUltrasound is a switch-capacitor filter with an internal high frequency oscillator.  If you build this PC board, you should add the missing 22K resistor to ground to each circuit.  I’ve added an output jack with 10K series resistor for the H.F. output (this is the yellow banana jack on Plumbutter).

 Output Mixer and Voltage Regulator

rollz-5-output-mixerPlumbutter has an output mixer with pots for Gong, AVDog, and Ultrasound that mix each one of the pair to left and right outputs.  Rollz-5+ has 12 audio modules (4 each of those just mentioned), so I designed this output mixer to be similar to Plumbutter.  There are six ganged pots.  Each pot sends a pair of the same type of module to both right and left.  The connections to the mixer aren’t shown on the individual schematics above, but they will tap off just ahead of the series resistor going to the corresponding output jack on the panel.

I’m including a 7809 voltage regulator.  This takes a 12V wall wart supply input.  I am not building the Vactrol voltage starvation circuit that’s on the PC board.


I’m planning to build this behind a clear acrylic panel, so that the PC board will show.  The pots will all be panel-mounted.  More details to follow.



9 Responses to Rollz-5 Schematics

  1. Pingback: New Instruments!! | Aidan Richard Taylor

  2. Pingback: Rollz-5 Assembly Progress | Richard Brewster's Synthesizer

  3. Tuukka Jääskeläinen says:

    Hey there! Awesome that you’ve documented all this, thank you for that!

    Just one question. Why are there still those “node”-jacks in the rollz schematic, and what happens if you put some voltage in it?

  4. Richard says:

    The node jacks on the rollz are the brown jack patch points. Located at the base of transistors, they can act as both output (from previous transistor) or input. Since connected directly to the transistor, patching here could result in damage, but there will be no harm if patching from other outputs on the Rollz-5, because of the 10k resistors on those.

  5. Tuukka Jääskeläinen says:

    Thank you for the reply! So would there be any way to secure these inputs/outputs so that you could supply voltages in there from eurorack clock sources? 10K resistor before the jack?

  6. Richard says:

    If you want to patch into these from Eurorack, yes, a 10K resistor in series would be a good idea. But I don’t know if patching from Eurorack into these nodes would be very useful for anything. I suggest you go to the Ciat-Lonbarde discussion on MuffWiggler and ask this question.

  7. Jesper says:

    Hi Richard!
    I’ve replaced gong trimmers with 1M dual gang pots (with 22k resistors in series – one for each trimpot). When compared to the gongs with trimpots the dual-ganged gongs do not get as low and has lesser decay. There’s also some volume loss. Could this be cause I’m not using 2M’s, or could I have wired the resistors all wrong (resistor goes between pcb and lug 1(A & B)..?
    Any help is greatly appreciated.

    all the best

  8. Richard says:

    Jesper, I just double checked my build. I used dual gang A1M (audio taper) pots with 47K series resistors to replace the trimpots on the gongs. The series resistor value limits the upper and lower frequencies of the gong. See what I said about frequency ranges here.

    Mine went down to 95 Hz (1M + 47k) and up to 2.1 Khz (47k). With 22k series resistors, you would see higher values for both of these, which is what you reported. If you want lower frequencies, change the 22K for 47K or even 100K.

  9. Jesper says:

    Okay! Yes, the gong freq spectrum is definitely higher. I’ll try out some different resistors and compare with the trimpots.
    I’ve been using linear pots.. Do you think they could be the cause of decay loss?
    Anyway I’ll change these and let you know the results. Thanks a lot!

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