May 2019
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24-to-25 pin conversion

DIY Roland 24-pin to DB25-pin Conversion

Features and Specifications:

  • Use modern, readily available, high quality DB 25 pin cables in place of 25 - 35 year old hard-to-find vintage 24-pin cables
  • Works with all vintage Roland Guitar and Basses (G-202, G-303, G-505, G-707, G-808, G-33, G-77, G-88).
  • Works with Roland Guitar Synthesizers: GR-300, GR-33B, GR-700, GR-77B and GM-70.
  • Download wiring diagram for guitar and synthesizer 24-to-25 pin conversion.
  • Basic soldering skills required.
  • SOLD OUT!
Roland GR-300 with DB 25 Connector
GR-300 with DB25 Connector in place of original
proprietary 24-pin connector.

Introduction to the "Do It Yourself" Roland 24-pin to DB25-pin Conversion:

Download 24-to-25 stl (3d Printing)

Vintage Roland guitar synth players have been replacing the proprietary 24-pin connectors with the more common DB25 hardware for about as long as Roland has been making guitar synthesizers.

For some folks, it did not make sense to keep paying top dollar for the Roland cables, when there is a high-quality, low cost alternative. Now, with the increasing scarcity of the original Roland cables, and the escalating price, it makes more sense than ever to consider moving away from the original Roland hardware.

This page outlines a Roland 24-pin to DB25-pin procedure I developed. I started with a surplus of Roland 24-pin ribbon connectors and locking rings. Basically, I connected 24 wires to the DB25 pin connector, then attached those 24 wires to the Roland ribbons removed from the original 24-pin connectors. By using the Roland ribbons, I did not have to make any permanent changes to either my guitars or synthesizers. To keep wiring organized, I followed the Roland pin-outs, so pin one on my DB25 connector is +15 volts, pin two is -15 volts, etc. the same as on the original Roland 24 pin connector. This also maintained compatibility with the Roland US-2 Turbo and the RC-1324-VR.

How to read the 24-to-25 pin diagram:

Switching over to DB25 hardware is not too difficult, though it is important to keep in mind when wiring the connectors the asymmetric nature of the original Roland hardware. The Roland 24-pin connectors had nine pins on either side, plus six pins in the middle, for a total of 24-pins. The six pins in the middle were not symmetrically distributed, so wiring both sides identically will result in incorrect wiring.

The first page of the diagram outlines creating the connector for the guitar. You will notice the top ribbon, "A1" has twelve solder pads for connecting wires. These are labeled indicating function, original Roland pin assignment, and a color code. For example, the top most pad is labeled as "GND", "Green/Black" and "4". On the original Roland 24-pin connector, pin "4" is one of many pins used for ground. I used a green wire with a black stripe for this connection.

Why does pin "4" come first? If you look at the original 24-pin connector, you will notice that pin "4" is one of the asymmetrically distributed center pins.

The next connection down is labeled as "+15V," "Red" and "1". Pin "1" on the Roland connector is the positive 15 volt power supply. So, on the "guitar" connector, pin "2" on the "A1" ribbon carries the +15 volt supply. If you look at the second page, outlining the connections to the synth, you will notice that the +15 volt supply is now the last connection on the ribbon labeled as "B1."

Follow the pdf diagram, and you will not have any problems. Also, check out the YouTube clip below that I made for a retrofit kit to get an overview of how things were assembled.

What To Do With A STL File? 3D Printing

You can use the 'plate_2mm_v2.stl' to make your own 24 to 25 pin mouting plate using a 3d printer. Justin Casey was kind enough to share this file and these photos when doing a 24 to 25 pin conversion for his GR-500. Justin wrote: "I've attached the standard STL file with a plate at 2mm thick. I've also attached an image of the front and back of the plates, as well as a screenshot of the basic settings I used in the slicer software for my 3D printer. I did these on a Monoprice MP Select Mini V2 with PLA as the material. As an STL is a universal filetype, people can use the file themselves if they have a printer or send it off to a shop to have someone else print it for them. Let me know if you have any questions and I'll try to answer them as well as I can, but I will admit I'm still a relative novice to the world of 3D printing."

Download 24-to-25 stl (3d Printing)

24 to 25 Pin Conversion - 3D Printer:

roland connector roland connector roland connector roland connector
Click on any image for larger view.

What To Do With A DXF File?

You can use the '24-25.dxf' to make your own 24 to 25 pin mouting plate. I used the company Big Blue Saw to make my 24-to-25 plates from aluminum. The price for a single piece can be expensive, but if you order in quatity the price will drop considerably. Plus, they have specials from time to time.

Download 24-to-25 dxf Diagram

Links to more information:

Photos - Version 1:

roland connector roland connector roland connector
roland connector roland connector roland connector
roland connector roland connector roland connector
roland connector roland connector roland connector
roland connector roland connector roland connector
roland connector roland connector roland connector
roland connector roland connector roland connector
Click on any image for larger view.

Photos - Version 2 - Active PC Board with Polydistortion Upgrade (Hex Fuzz):

actove connector actove connector actove connector
actove connector actove connector actove connector
Click on any image for larger view.

Videos: