Submodular Synthesizer

Introduction

The ISHIZENO ONE is a submodular synthesizer. It decouples faceplate from electronics in order to provide fine-grain modularity. It is built around an iPod Touch used as touchscreen, dynamic patching controller, and digital signal processing unit. It provides 8 monophonic channels, each of them being made of 6 analog ports and being supported by a dedicated Arduino Uno and an optional Arduino shield. Dynamic patching between analog ports is supported by a set of analog crosspoint switches.

8 Monophonic Channels

Each of the 8 monophonic channels provides:

• 6 analog ports
• 2 small knobs
• 2 large concentric knobs

16-channel Oscilloscope

The module includes two AD7606 8-channel 24-bit analog to digital converters. This allows the built-in iPod Touch to be used as a low-frequency 16-channel oscilloscope. By default, the oscilloscope's channels are patched to the input and output of every monophonic channel.

Submodular Architecture

Out of the box, the module does not provide any synthesis capabilities. Instead, these are added through breakout boards, with up to 8 boards (one per channel). The module also includes an Arduino Uno used as middleware. Programming can be done through the Arduino, through the iOS operating system of the iPod Touch, or both. Obviously, the Arduino and the iPod Touch can be used as software sequencers (among many other applications). The analog crosspoint switches can also be reconfigured dynamically in order to support high-frequency dynamic patching.

Breakout Boards

Every channel can be supported by an optional breakout board that is plugged onto the module's backplane. Breakout boards must use a standard 16-pin connection pattern that is currently being defined. One likely candidate is an L-shape arrangement of 2 rows of 8 pins (standard 2.54mm spacing). This arrangement ensures that breakout boards are always properly connected to the backplane.

The ISHIZENO submodular architecture does not mandate any specific pin assignment. Instead, the pins of breakout boards are dynamically patched through the analog crosspoint switches, which can be used for both analog and digital signals, as well as for power. Because breakout boards do not include any faceplate, controls, mounting hardware, or power connector, they should be much more cost effective than full-fledged Eurorack modules. As such, they are referred to as submodules, and the synthesizer is described as being submodular.

A single-channel breakout board (1S) is 53mm long and 53mm wide. Connection between a breakout board and the backplane is achieved through stackable headers, allowing multiple breakout boards to be stacked on top of each other for applications that require many components.

Examples of breakout boards could include any of the following:

• Analog Filter
• Digital Signal Processor
• Envelope Generator
• Low Frequency Oscillator
• Mixer
• Oscillator
• Phase Shifter
• Sampler
• Sequencer
• Waveshaper
• Etc.

Multi-Channel Breakout Boards

By default, a breakout board has 16 pins and is attached to a single channel. But some applications might require breakout boards with more pins, or more PCB real-estate. In such a case, a multi-channel board can use the connectors offered by 2, 3, 4, 6, or 8 channels. For standardization purposes, single-channel boards are said to have a size of 1S, while multi-channel boards have sizes of 2S, 3S, 4S, 6S, or 8S.

• 1S: 53mm × 53mm
• 2S: 53mm × 106mm
• 3S: 53mm × 159mm
• 4S: 106mm × 106mm
• 6S: 106mm × 159mm
• 8S: 106mm × 212mm

Dynamic Patching

Dynamic patching is enabled by a matrix of 8 or 16 AD75019 analog crosspoint switches. These switches have no gain and a low 150 Ω resistance. No more than two switches are ever used in cascade, thereby limiting the overhead resistance to 300 Ω on every analog signal path.

Patching across channels can be done in a traditional way through the faceplate's 32 3.5mm jack chassis sockets, through the analog crosspoint switches, or through multi-channel breakout boards. Using dynamic patching, any pair of ports of any pair of channels can be patched together, including two ports of the same channel. When the module is equipped with 8 switches, up to 16 concurrent patches can be established at a time. With 16 switches, this limit increases to 32.

Digital Potentiometers

All knobs are connected to an AD5254 quad digital potentiometer with 256-position resolution and providing a resistance range of 1 kΩ, 10 kΩ, 50 kΩ, or 100 kΩ. This setup allows all 32 potentiometers to be controlled manually through knobs, digitally through Arduino or iOS, or modularly through traditional voltage control (with both faceplate patching and dynamic patching).

Additional Features

The faceplate also include two spinner control knobs driving rotary encoders and two USB ports, one connected to the iPod Touch's lightning connector, and one connected to the Arduino Uno. The USB ports can be used to connect controllers like keyboards or grids.

Project Status

This module is at the early prototyping stage. Specifications will vary. All software will be released under an open source license and all hardware designs will be released under a Creative Common license. Unfortunately, no release timeframe can be announced at this point.

Additional Resources

• List of Parts

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https://ishizeno.wordpress.com/

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$1,995