SynthCase 3 Patchable Roadcase Synthesizer


This project is the third in a series of synthesizer "multi-modules" that will be built in heavy-duty equipment road cases. Check out the first SynthCase project here and the second SynthCase project here. The third SynthCase will be primarily composed of timing and sequencing modules, basically the rhythm section of the synthesizer.

Below is the road case chosen for this project, salvaged from obsolete radio-telephone use.

Two panels of 1/8th inch aluminum plate were cut to roughly 10 1/4 by 18 inches and mounted into the case using four "L" brackets for each panel.

The sequencer is the central controller of the synthesizer rhythm section, and SynthCase 3 begins with four of them. Two are based on Jim Patchell's 8 X 2 sequencer pcb project, but with many added features, and two are based on Fonik's VC Pattern Sequencer, with a few minor additions as well.

The two 8 X 2 sequencers are enhanced with individual step selection buttons and gate inputs, individual trigger outputs for each step, and three channels of analogue trigger outputs for driving drum machines or envelope generators. The two sequencers can also be linked into one 16 X 2 sequencer by flipping a switch.

The VCP Sequencers each have an added sequence length selector switch, and one sequencer has individual step gate outputs included as well.

The top half of the case contains the two 8 X 2 sequencers, two manual trigger/gate pushbuttons, three SPDT routing switches, a JK flip flop, and the heart of the rhythm section, a voltage controlled master clock with /1 /2, /4, and /8 divided outputs. All of the clock, flip flop, and trigger circuits are built on stripboard, as is the additional circuitry added to the sequencers.

In addition to the two VCP Sequencers, the bottom half of the case has an assortment of digital logic and processing modules. There are a large number of CGS pcbs, including four burst generators, a quad invertor, quad gate to trigger convertors, quad OR gate, quad AND gate, a NOR and a NAND gate, an XOR/XNOR gate, two multiple input OR gates, a slope detector, and two different pulse divider modules. There are also some Yusynth design modules built on stripboard, including a gate delay, trigger delay, and a comparator circuit. Rounding off the SynthCase is a JH VC Divider circuit also built on stripboard, and a +5 volt and ground connection.

The usual 300 dpi graphics were produced, but fitting everything in was a real challenge. This project has by far the highest front panel part density that I've ever built.

There is barely enough room for the circuit boards in the bottom half, but they do fit. There are also power supply regulator pcbs taking up a bit of space.

Here are the laminated graphics back from the printer:

Using the graphics, the panel holes are centre-punched.

The holes are then drilled and deburred.

Then the graphics sheets are glued to the panel and the paper holes cut to match the metal.

And finally the literally hundreds of parts are bolted on.

Here is a rear view of the two panels with all of the connectors, controls, and indicators mounted:

And here is the front view of SynthCase 3 with the hardware assembly completed:

Next up, installing and wiring up the pc boards, this project is going to use a LOT of wire!

The first modules and pcbs to be wired are the burst generators. They are attached directly to the front panel with the "pulses" selector switch.

The power supply regulator, gate to trigger converter, and the XOR/XNOR gate wiring has been completed, and the modules are all tested and working.

Next to be installed is the first pulse divider module, including the NOR and NAND gates. The LEDs for the second divider are also in place at this point.

The second divider module is shown completed here.

Next was the multi-module strip board containing the voltage controlled divider, 5 volt source, multi-input OR gates, gate and trigger delays, and voltage comparator module.

Here is a close up view of the completed stripboard.

After that the slope detector module was completed.

Then the AND gates, invertors, and the rest of the OR gates were wired.

Getting close to completing the first panel, the first VCPS sequencer is finished.

Here is a step-by-step slideshow of the wiring process for the second VCPS panel.

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First the LEDs are installed and their ground connections wired together.


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Next the step gate output buffers are wired into place.


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Then all of the rest of the panel point-to-point wiring is done.


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Next the wires connecting the lower rows of controls to the circuit board are attached.


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The wires connecting the remaining controls to the circuit board are installed.


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Finally, all of the wires are positioned and bundled up neatly.


Here are all of the panel wires ready to be connected to the circuit board. Good thing that they are all different colors!

And here they are again, all soldered in and neatly bundled.

There were two modifications made to the VCPS circuit, adding some extra functions. First, a selector switch was added to allow adjustment of the sequence length from eight down to seven, six, five, four, or three steps. Second, a gate output signal was added for each step, using a simple op amp buffer circuit. The changes to the circuit are shown below, with the buffers marked in blue and the sequence length switch in red.

Here is a picture of the step gate buffer circuits. They were built using just IC sockets alone, and then soldered in with the connections holding them in place on the panel. If you watch the slide show above you can see where they were installed on the panel.

The additional pcb wiring connections required for the sequence length switch would be difficult to solder directly to the board, so the wires were connected to an extra IC socket instead.

The extra socket with the IC plugged into it was then inserted into the pc board.

The first half of SynthCase 3 has been completed!

Look at all the pretty lights!!

The second panel is all ready to wire up, with the voltage regulator pcb installed on the top left.

There are six main pcbs for this panel, as well as a small driver board not pictured here. The stripboard type pcb on the left is for the VC Clock, Flip Flop, and Trigger/Gate modules. The two regular green circuit boards are the original Jim Patchell 8 X 2 sequencer pcbs that are the heart of the sequencer module. The two rectangular stripboards on the right provide additional logic, and the other stripboard contains mixer and drver circuits.

Here the VC Clock, Flip Flop, and Trigger/Gate modules are all wired up and working.

There was a lot of wiring between the sequencer panel components that needed to be done before connecting up the pc boards.

Shown here are all seven circuit boards, including the small driver pcb, in place and connected to the power supply.

All of the wiring is now complete, and the sequencer is tested and functioning. A few small bugs had to be worked out, then all of the pcbs and wiring were secured.

The main SynthCase power supply was expanded to power SynthCase 3. Extra fuses and LEDs were added for future expansion at the same time.

Another synthcase project successfully completed! This project certainly had it's share of challenges, particularly the amount of wiring required. The result was very worthwhile however, as SynthCase 3 is quickly proving to be a powerful and versatile rhythm and timing controller.

The SynthCase family is growing! Time to make some music!


Don't forget to check out The Peasant's first SynthCase project: SynthCase 1 and the second SynthCase project: SynthCase 2

The SynthCase is controlled using The Peasant's Banjo Processor

Sometimes The Electronic Peasant lets The Celtic Peasant play the SynthCase with her Keyboard Controller