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    Using your PC's built in MIDI Adapter

    2/01 - Jens Moller - http://www.colomar.com/Shavano/midi_pc.html

    I have a combination Game Port/MIDI Port - How do I use it?

    Back in the late 1980's when IBM Compatable PCs were not yet running Windows 3.0, Creative Labs invented the SoundBlaster sound card. It had an 8 bit A/D and D/A converter (which allowed you to record and playback real digital sound - kind of noisy, but it was an 8 bit digital recording system). These also had Yamahas OPT FM systhesizers built in - very advanced for the time and all in a few integrated circuits. They also had a game port too, because even back in those days, many people used their PC's to play games on. Lastly, Creative added part of a MIDI port. This MIDI port needed a few extra parts to make it work with external MIDI devices, but the hard part to build was on the sound card. I bought one of these early Sound Blasters and back in 1990 it was quite a prize for $150.00 (US).

    If you cycle thru the years up until 2001, you'll find that the concepts used in this early SoundBlaster has continued. The A/D and D/A converters are all 16 bit (Capable of CD quality), The Synth chip sets range from something very much like the original OPT FM chip sets to very high end sound chipsets used in pro synth gear (such as the Ensoniq chip sets in some of the current SoundBlasters). The Game port is still there because people still play games on their PCs and that probably will never change. The side effect is that the MIDI interface, for the most part, is almost identical to the one on my 1990 SoundBlaster - you still need a few extra components to use it to talk to external MIDI gear.

    A very few Sound Cards have the complete MIDI hardware on board, and these either are very high end and expensive, or tend to have odd connectors on them requiring fairly expensive cables.

    There have also been specialized MIDI only PC cards that you could plug in and run with. Roland created one called the MPU401 - this was really optimised to operate on very slow IBM PCs (when an IBM PC running at 4.7 Mhz was considered fast - back in 1985). On a faster IBM PC (which can now run at faster than 1 GHz), the MPU401 became a dated design that created a massive bottleneck. Voyetra also had a series of MIDI PC cards that avoided the MPU401 problems by doing direct data bus access (MPU401's have an onboard data queue), these required a faster CPU chipset (which were only up to around 33 Mhz by 1990) than a real MPU401. The MPU401 has a lot of software written for it, and as such the SoundBlaster cards sets eventually put in a software emulation of it, and you often see that sound cards are MPU401 compatable. The MPU401 and Voyetra cards had all the MIDI circuitry on the PC card - the SoundBlaster MIDI port has always been missing a few parts. Today, practically every PC sound card that has both a Game Port and a built in MIDI port uses the same implementation that original SoundBlaster used - and as such, every SoundBlaster compatable MIDI/Game Port adapter will work with any of the thousands of sound cards that use this interface.

    So whats missing?

    It turns out that there are not many parts missing; mostly, you only need an Opti-Isolator, a few resistors, wire and connectors. This is good because it makes it cheap for companies to make SoundBlaster compatable MIDI adapters - I see these starting at around $20.00 (US) in many stores and online. If you have a source for the Opto-Isolator chip (the hardest part to find), you should be able to build the same interface for around $15.00 (US) in parts.

    the Following Web Page lists many solutions for this (For PC owners, look for SoundBlaster interfaces):

      Harmony Central - Making a MIDI Interface

    They also have information on other MIDI interface designs for Macintosh systems, Linux and other Unix systems. There is also a MIDI interface design using a Parallel (printer) port - which is very useful if you want to carry a laptop system around with you to operate MIDI gear.

    Note: SoundBlaster is a trademark of Creative Labs

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