SynthCase Patchable Roadcase Synthesizer


This project is the first in a series of synthesizer "multi-modules" that will be built in heavy-duty equipment road cases. A friend had passed on to me a bunch of used cases from obsolete equipment that were being disposed of, and I had a number of new synthesizer module printed circuit boards waiting to be used, so a plan to combine them together was made. The first "SynthCase" will hold a basic patchable voltage-controlled analogue synthesizer, and subsequent expansion cases will include sequencers and other controllers, delay/chorus/phaser modules, and other signal/CV processors.

Below is the road case to be used for the main synthesizer. This case opens into two separate halves, each one suitable for holding a large bank of modules.

The inside dimensions of each case half are 13.5 X 26.5 inches. Two panels of 1/8th inch aluminum plate were cut to this size and mounted into the case using six "L" brackets for each panel. A stand to support the top half of the case at a more upright angle was also installed.

The next step is to build a power supply. A salvaged metal equipment enclosure was chosen to house the main power supplies for the SynthCase. This enclosure will be expandable in order to power additional SynthCases as they are completed.

The power supply consists of two 26 volt 2 amp OEM linear regulated power supplies set to 22 VDC, one for the positive rail and one for the negative rail. Sub-regulators inside each individual SynthCase will drop the voltages to +/-12 or +/-15 volts as required. The cabinet has a built-in cooling fan and power switch. LEDs, fuses, and zener diodes for overvoltage protection were added to complete the chassis. Extra connectors and indicators are included for future expansion.

A cable to connect the power supply to the main synthesizer cases was also assembled.

Now the hard part comes - deciding which modules should be included in the main unit and which should be left out for a future SynthCase. After soliciting some expert advice, and much careful thought, the following design was chosen. Many of the modules will use circuit boards from Ken Stone and Ray Wilson, some of the boards will be custom built, and the rest will be a few various pcbs that I have waiting to be used. A large stock of Lemo coaxial connectors was available from salvage, so they were chosen to be used for audio signal connectors. Standard banana connectors were selected for control voltage, gate, and trigger use. Adapter cables will be constructed to allow using audio signals for control voltage purposes and vice-versa. The overall layout is for the controls to be near the front and back edges and the connectors near the center in order to minimise cable sprawl. Future Synthcases would be added to either side of the first unit, voltage controllers to the left and audio sources/processors to the right.

Next, a 300 dpi scale drawing was created with all of the hole location markings and labeling for each panel:

The drawing files were emailed to a local printer who printed each one on to a single piece of white bond paper and then laminated them using low-gloss matte type plastic laminate. Thanks go out to John Greczula/Xenolab Design for suggesting this effective but inexpensive panel finishing technique and for other graphics assistance.

The laminated graphics sheets were taped to the aluminum panels and all of the holes were center-punched.

Then, after removing the graphics sheets, each hole was pilot drilled, drilled to size, and deburred. Each panel was then cleaned and the back of each graphics sheet was slightly scuffed with steel wool. The laminated graphics sheets were then attached to the panels permanently using 3M type 77 spray adhesive, and all of the holes were cut to size out of the laminate with an Exacto knife. Here you can see the second panel with the holes cut out and the connectors and switches installed:

Here is a top and bottom view of the first panel with all of the parts mounted:

And here is the second panel completed:

And finally, a view of each panel mounted in the case:

Now the actual electronic construction work can finally begin!

The following pictures show the first panel being wired up, starting with the power supply sub-regulators and the four main VCOs, then the mixer and output sections, the bandpass filters, and so on from there.

Most of the shielded cable used for signals is RG174, as it is easy to work with and plentiful as surplus. Other hook-up wire is taken from obsolete computer multiconductor cables.

And here is the first half of the SynthCase, all wired up, tested, calibrated, and ready to go!

Work begins on the second half, starting with the Voltage Controlled Filters.

Here are some pictures of the Psycho LFO being wired up.

And finally some views of the second cabinet completed.

The first SynthCase is now finished and ready to make music! After spending over a month planning and three months building this synthesizer, it's great to be finally getting to use it.

This project used recycled parts whenever possible. This included approximately 70% of the capacitors, 60% of the switches, 50% of the integrated circuits, 90% of the connectors, and all of the power supplies, regulators, wire, enclosures, and the small hardware such as screws, bolts, washers, etc.

The Peasant has also completed the second SynthCase project, check out SynthCase 2 The third SynthCase project has been completed as well SynthCase 3

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