AI202-O-Matic General Midi sound module

DIY STUFF
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Sculpt-O-Sound presents: the AI202-O-Matic

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The AI202-O-Matic is based on a General Midi sound module that was meant to be an add on for a PC sound card. It was manufactured by Korg and is based on AI2 synthesis. Back in the day when people started playing games on XT and AT clones of IBM PCs the sound of these machines was quite primitive. So some manufacturers started making upgrades. Oftentimes these were modules one could connect to an existing PC sound card, or at least to the ones fitted with a so called Waveblaster-port. This was present on most/all Soundblaster-cards and -clones. The module was meant to add good quality MIDI-controlled sound to games.

[Edit] As @handsomegenius notes below, this seems to be historically incorrect. The General Midi standard wasn’t created until the '90s and XT and AT machines were 80s machines. Yet another sign that my memory isn’t what it used to be …

This picture shows a KORG MBCS35104 with an AI202 chip on it I found in my stash of old pc interfaces the other day.

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Interfacing this is quite easy and does not require any ancient pc hardware, as can be seen in the following schematic. It needs some power and a midi signal as input and the signal generated by the device can be taken from the left out and right out lines. C6 and R1 are there to generate a reset signal at power up, to ensure that the module is reset properly. I added a blue LED and a 4k7 resistor to pin 3 of IC2a which signal midi data coming into the device.
B.t.w. on my Korg PCB the numbering of the row of pins was printed wrong, so a check is a good idea.

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So I added some connectors to a piece of perfboard and the rest of the components (contrary to what the partial build in the picture shows I ended up using a TIL111 for IC1 and a 4k7 resistor for R5).

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Because of the layout I chose I could piggy back the perfboard on the sound module.

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I added a 3D printed bracket, screwed the pcb to it and glued the bracket to the front panel which I cut with a K40 laser.

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The Korg MBCS35104 was released in 1991, has a ROM size of 4 Mb containing general midi sounds and some drum kits. The patch set is called ‘Cleanwave’. The polyphony is 32 voices, so it is quite a powerful synth!

There were plenty of these devices made and they seem to be easily available via 2nd hand markets.

If you find this type of technology interesting, there is a lot of info about it at waveblaster.nl More info about interfacing waveblaster modules can be found here.

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Incredible hacking! Can we hear it, please? :slight_smile:

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The sounds are general midi sounds so not very spectacular in nature. There are acoustic and electric piano sounds, harpsicords, trumpets, violins, and the sound of a helicopter and a gunshot in the list of all 128 sounds. Various manufacturers made sound blaster modules and they seem to vary quite a bit in sound quality. The Korg one I have seems to be one from the better range.

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Sort of… the XT and AT were 80s machines. General MIDI wasn’t standardised until the '90s. The AT had been discontinued for a while by that point. This kind of tech is more contemporary with 486 and Pentium machines

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In the 90’s my home pc had the pinnacle project studio audio card boasting two independent synths on the board … korg possibly but general midi to the core… Turn up, Switch on, pick that preset, you know the one, one finger play, and chukkachukkachukka I’m back man, me back, choppers 8 bittin’ the heck out of ‘active’ pc speakers and I got nothing!
Still, ah love the smell of nae plan in the morning!

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Thx for the update. I will correct the text.

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The point of General MIDI was that you didn’t need a particular synth chip on the card. It was a standard specification that meant developers could choose a piano or a guitar or a helicopter sound, and it would always be at the same patch number on every device. The actual sound of each instrument could vary a lot from device to device though.

A lot of sound cards back in the day had Yamaha FM chips in them. Particularly the Sound Blaster cards, which were everywhere. So they had kind of that Yamaha DX7 sound. Accessing it through General MIDI meant that it was sort of just a preset machine though. Whereas the Sega Mega Drive also had a Yamaha FM synth in it, but developers would interact with it at a deeper level and do their own sound design.

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