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KORG M1 Remake

Related project: KORG M1 Filer (program for management of the settings and songs in the KORG M1)

About the project

This is a very extensive project that includes hardware modifications of the KORG M1 synthesizer, development and production of several microcomputer devices, analysis of a large amount of data without any description, development of several computer programs, and production of samples.

The goal was to remake the KORG M1 synthesizer so that it can be possible to insert a custom samples. This goal has been achieved and the whole project has been reached to a successful end.

The legendary KORG M1 synthesizer works on the principle of playing back PCM samples. With such "raw" sounds, some edits are performed - envelope, vibrato, filters, etc. and finally the sound is processed by the built-in effect module.

Samples are fixed in the synthesizer and can be expanded by only about 16 plug-in cards that include fixed samples, too. In addition to these 16 cards, no other sounds (samples) can be put into the KORG M1. In my opinion, the KORG M1 has some sounds that are totally unusable (respectively, usable just one times - even the legendary sound "Universe"), and several basic sounds are not good (e.g. piano, normal bass is missing, Rhodes is missing, Timpani, good "open Hi-Hat", the strings are not good, etc.).

Searching for a solution

It is not possible to make a custom plug-in card that would fit into the expansion card connector. The KORG M1 does not have the data of the samples only in sample memory, but also in the second (fixed) memory with the program for the built-in control processor. Even some essential data from 16 plug-in cards are also stored in this program memory, and the samples are forever determined.

As a solution, I chose a plug-in memory module that will contain, in addition to the data memory, a program memory in which important data about the samples will be replaced by others. This solution involved significantly more complex hardware modifications.

It was about half a year of intense work in my spare time. In addition to reading the original samples from the fixed memory to the PC, the program memory has to be read and to find out where and how the data of the samples are stored. This activity was extremely difficult. I found out what is the structure of the sample data in the memory of processor's program. I have proposed a solution to how the original data could be replaced by new ones. For this purpose, I created a set of programs and the result was a software system that can prepare any suitable samples and store them in my memory module.

Interesting finding

The data memory of KORG M1 built-in samples has a capacity of 4 MB. As I found, the chip that plays the samples, is capable of serving 8 times more memory, i.e. 32 MB. Based on this finding, I decided that my memory module will have a maximum capacity of 32 MB and so the KORG M1 can have the best sample capabilities (memory capacity also determines the quality of sounds).

Finished solution

First recordings from KORG M1 with my plug-in memory module with new samples:

- new bass guitar (PC modeled), new sounds of piano and drums

- mew bass guitar (PC modeled), new sounds of Rhodes electric piano, piano and drums

- 7/8 measure. New bass guitar (PC modeled), new sounds of Rhodes, piano and drums

- Steinway piano

- Grand C3 piano (stereo!)

A few images from the KORG M1 remake:

- 4MB part of memory module (such are in the module 8 pieces)
- I when soldering the wiring - connecting the KORG M1 motherboard and the connector for the plug-in memory module
- motherboard of the KORG M1 with the connector for memory module
- disassembled KORG M1 with the connector for plug-in memory module
- measuring of the 4MB part of memory module
- assembling the memory module
- schematic diagram of the memory module
- ready memory module without a box

Photos of finished product:

- finished memory module and KORG M1 synthesizer
- device for writing samples to a memory module (PC connection via LPT port). The current version works via USB.