HardLabs

Midi extension

calphool·JMR-800·PG800-JMR/midi_extension/midi_extension.kicad_pcb

Midi extension PCB layout, top view — open source board by calphool

About the Midi extension PCB

Midi extension is an open source PCB design by calphool, published on GitHub. It is a 2-layer board measuring 47.5 × 75 mm, with 19 components from 11 distinct parts.

Other key parts include the 6N138. By type, the board carries 12 resistors, 4 connectors, 1 IC, 1 diode and 1 capacitor.

It belongs with the audio and retro computing designs in this gallery.

From the project

JMR-800 project, clone of PG-800 hardware

JMR-800 is a modern, open-source clone of the Roland PG-800 hardware programmer, built around the Teensy 4.1 microcontroller. It provides real-time parameter control for vintage Roland synthesizers such as the JX-8P, MKS-70, and JX-10 using the original PG-800 communication protocol.

The JMR-800 replicates the original PG-800's functionality and physical interface, enabling direct, tactile editing of synthesizer parameters through a hands-on control surface.

Midi extension, from the project README
From the project README

Main components on the Midi extension

6N138

Midi extension bill of materials (BOM)

19 components, 11 distinct parts.

QtyPartRefs
1
6N138
U1
1
Conn_01x08_Pin
J1
1
MIDI-IN
J2
1
MIDI-THRU
J3
1
MIDI-OUT
J4
1
1N4148
D1
1
.1uf
C1
1
220
R1
1
470
R2
4
47
R3, R4, R5, R6
6
0
R7, R8, R9, R10, R11, R12

Midi extension design files

The KiCad project lives in the calphool/JMR-800 repository on GitHub; these links point at the commit this page was built from.

Midi extension: common questions

How big is the Midi extension PCB?

The Midi extension measures 47.5 × 75 mm, has 2 copper layers and is 1.6 mm thick.

How many components are on the Midi extension?

19 components, from 11 distinct parts. The full bill of materials is listed on this page.

Where can I download the Midi extension design files?

From the calphool/JMR-800 repository on GitHub, which has the KiCad layout and the schematic; the links under Design files point to each one.

Can I use the Midi extension design in my own project?

The repository has no license, so all rights stay with calphool. Use it as a reference, and ask the author before reusing the design.

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