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Midi Stack

Project Summary:

The Midi Stack is a modular, stand-alone system for playing back of standard Musical Instrument Digital Interface (MIDI) files.  Although the initial concept for this project entailed crafting of a single monolithic device, my plans ultimately expanded to build multiple interconnected modules arranged in a vertical stack.  Each audio component was designed to serve a specific purpose and to perform a distinct task.  More details about each module are shown below.

Midi Stack Demo Videos

Midi Stack Demo Videos

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Midi Player Module Description:

The Midi Player is a custom-built hardware solution for reading and playing back standard MIDI files. The MIDI interface specification is a global standard that has been widely adopted by the music industry since the 1980s and is used for interfacing disparate digital audio components such as keyboard synthesizers, sound cards, recording units, and playback devices.  Midi was also used by many computer game developers in the 1990s to create richer, more immersive soundtracks for popular PC video games.


Midi Player Features & Specifications:

  • Custom-built half-rack aluminum enclosure matches aesthetic of existing stereo components

  • Metro M4 Grand Central Central Processing Unit

  • Laser-engraved front panel and transparent acrylic cutouts

  • Micro SD Card Mass Storage and Filesystem

  • Backlit 20x4 LCD Display screen

  • Eight Backlit LED tactile pushbutton switches and interface Printed Circuit Board (PCB)

  • Rotary encoder knob with built-in LED Backlight (full RGB color)

  • 5-Pin DIN Midi Output port

  • IR Sensor for Remote Control


Midi Visualizer Module Description:

The Midi Visualizer is a custom-built hardware computing device designed to visualize MIDI music signals transmitted using the standard Midi transmission protocol.  The objective is to provide a dynamic and engaging real-time visualization of musical notes, akin to a Midi synthesizer light board, or commonly available screensaver software, in a self-contained application-specific hardware device, thus avoiding the hassle associated with constant maintenance required of consumer grade operating system software.  Features instant-on capability and provides audio inputs for possible future expansion of audio waveform sampling and analysis, such as a graphic equalizer or oscilloscope.


Midi Visualizer Features & Specifications:

  • Adafruit M4 Metro Express Arduino-compatible CPU

  • Half-rack width custom-built enclosure built from LEGO building blocks

  • 64x32 RGB LED Display Matrix – 3mm pitch

  • Adafruit RGB Matrix Shield for Arduino

  • 5-pin DIN Midi Input port (connected to Arduino serial input pins via optoisolator ) 

  • Brightness controlled via Midi SysEx messages


About the Midi Power Supply:

The Midi Power Supply is a custom-built Power Supply for the Midi Stack.  It eliminates the need for multiple power adapters and provides status information about the current electrical power consumption while maintaining consistency with the overall design ethos of the other components.


Midi Power Supply Technical Specifications:

  • Aluminum housing with vents for passive cooling

  • Input:    120 VAC    3-pin connector

  • Output:     5 VDC,  5mm barrel jack with center positive

  • Output:     9 VDC,  5mm barrel jack with center negative

  • Output:   12 VDC, 5mm barrel jack with center positive

  • Three separately regulated, fused, and shielded internal transformers for low-noise operation

  • Three independently operated separate power switches

  • Red, Green, Blue LED Volt-Ammeters for monitoring each power distribution channel


Midi Stereo Speakers:

These custom-built Stereo Speakers permit operation of the Midi Stack as a fully-independent, consolidated audio system with integrated amplification of the input signal.

Midi Stereo Speakers Technical Specifications:

  • Custom-built enclosure using LEGO building blocks

  • Audio input connector: 3.5mm stereo headphone jack

  • Output power: 10W + 10 W (8Ω)

  • Operating voltage: 12VDC

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