This 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.
I’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.)
AVDog 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).
I 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.
Gong 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.
Ultrasound 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
Plumbutter 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.