Simon Peter's Mini-Dexed Crams Eight Simulated Yahama DX7 Synths Into a Single Raspberry Pi
Running bare-metal without an underlying operating system, Mini-Dexed really squeezes the most out of a Raspberry Pi.
Digital musicians with a lack of available desk space may find this open source project to put eight Yamaha DX7-style synthesizers onto a single Raspberry Pi single-board computer more than welcome: the Mini-Dexed.
"MiniDexed is a FM synthesizer closely modeled on the famous DX7 by a well-known Japanese manufacturer running on a bare metal Raspberry Pi (without a Linux kernel or operating system)," explains project creator and maintainer Simon Peter. "On Raspberry Pi 2 and larger, it can run 8 tone generators, not unlike the TX816/TX802 (8 DX7 instances without the keyboard in one box)."
Built atop the Synth_Dexed project, which in turn was a port of the original Dexed sound engine for the resource-constrained Teensy microcontroller family, Mini-Dexed runs directly on any model of Raspberry Pi single-board computer — though, as its creator notes, full functionality is only available on the Raspberry Pi 2 or above.
Audio generated using the synth can be output to the Raspberry Pi's analog audio-video jack, the HDMI port, or via a dedicated high-quality digital-to-analog converter (DAC). For those looking for a middle ground, quality-wise, Peter notes that an HDMI-to-VGA adapter with audio output with a resistor jammed between two pins works as an "inexpensive, solder-free" solution for analog audio.
The project is notable for using the Raspberry Pi's hardware directly, without the benefit of an operating system in the middle. It's this which allows eight instances of Dexed to run on a single Raspberry Pi without slowdown, by maximizing the hardware resources available. For ease of use, it's designed with a rotary encoder input and LCD display panel on-board.
More information is available on the project's GitHub repository, where the source code and binary builds are made available under the reciprocal GNU General Public License 3; a detailed video showing the device's assembly and use has been published by YouTuber Floyd Steinberg.