The following text explains how to build a MIDI interface for the Sound Blaster. The circuit is my own design, but works just like the commercialy available interfaces that retails for $60-$90. Here is the list of parts necessary: Qty. Part 1 Sharp PC900 or HP 6N138 opto-isolator 1 DB15P (15 pin 'D' connector, male. like joystick connector) 3 220 ohm resistors (2 for input, 1 for EACH output you need) 1 3 conductor shielded cable (length is up to you) 2 Female 5 pin DIN connector (1 for input, 1 for each output you need) 1 PC board with pre-drilled holes (about 2" x 2" from Radio Shack) A few short lengths of hook-up wire All of these parts, except the first 2, are available from Radio Shack. Construction techniques are completely up to you, if you want to go ultra-cheap, you don't even need a PC board or enclosure, and you could use a MIDI cable you already have by cutting it in the middle. I used a PC900 out of a non-working organ and cut the end off of a joystick I didn't need and built the whole thing for about $4.00. Buying all the parts new, and using an enclosure with built-in MIDI jacks may cost about $20 or so. Here is a diagram of the DB15P connector (looking at the solder side). 1 5 8 o o o o o o o o o o o o o o o 9 12 15 Here is the 5 pin FEMALE DIN plug (solder side). 2 5 o 4 o o 3 o o 1 This is the circuit for the MIDI INPUT. +-----> To pin 5 of 'D' connector | To pin 15 of 'D' connector <---+ | +-------+-----> To pin 9 of 'D' con. | | | | SEE NOTE BELOW!----> | 6 |5 |4 \ +---------------+ / 220 ohm | PC900 | \ resistor | or | / | HP 6N138 | | +---------------+ +------> To pin 6 of PC 900 |1 |2 |3 | | | \ | +-----> No connection 220 ohm / | resistor \ | / +-----> To pin 5 of DIN connector | To pin 4 of DIN connector <----+ Don't overlook the two 220 ohm resistors. Also, for cables longer than a few feet, connect pin 2 of the DIN to pin 5 of the 'D' connector. The output circuit is much simpler. 220 ohm resistor To pin 12 of 'D' connector <---------/\/\/\/\/---------> To pin 5 of DIN con. To pin 15 of 'D' connector <---------------------------> To pin 4 of DIN con. Also, for cables longer than a few feet, connect pin 2 of the DIN to pin 5 of the 'D' connector. This circuit has been built and tested by me, using Voyetra's SPJr, and a cheap-o Casio keyboard. The input and output do work as shown here, but I don't have any other MIDI devices to use to test using more than 1 output device. Theoretically, it should work fine, but it has not been tested. The chances of hurting anything by trying is slim and none. This circuit DOES work, but I make no guarantees, nor will I be held responsible for any damages you may cause from your use of this information. If you have any questions, or would like to buy one already built for you, I can be contacted on: The Lighthouse BBS (207) 255-3700 (username is Ronald Davis) The Music Studio BBS (708) 351-0288 (username is Volstagg) >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> CORRECTION <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< > < > The PC900 connection diagram above contains an error. Pins 4 and 6 should < > be switched. Pin 6 is Vcc and should be connected to pin 9 of the D < > connector (+5v). Pin 4 is the collector of the output transistor and < > should be connected to pin 15 of the D connector (Midi In). As shown, the < > output transistor would be shorting Vcc to Ground each time it was turned < > on and would most likely blow the output transisitor of the PC900. I was < > glad I was looking at the MIDI spec at the same time I was looking at this!< > < > This is the CORRECTED circuit for the MIDI INPUT. < > < > < > +-----> To pin 5 of 'D' connector (GND) < > | < > To pin 15 of 'D' <---+ | +-------+-----> To pin 9 of 'D' con.< > connector (MIDI IN) | | | | (+5v) < > | 4 |5 |6 / < > +---------------+ \ 220 ohm < > | C E Vcc| / pull-up < > | PC900 | \ resistor < > | or | / < > | HP 6N138 | | < > | A K NC | | < > +---------------+ +------> To pin 4 of PC 900 < > |1 |2 |3 (MIDI IN) < > | | | < > \ | +-----> No connection < > 220 ohm / | < > resistor \ | < > / +-----> To pin 5 of DIN connector < > | < > To pin 4 of DIN <----+ < > connector < > < > With this correction the circuit works great! < > Grady Sharpe - 3 FEB 92 < >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<