Adapt a Waveblaster soundcard to the STThe PC-world is filled with simple things with fancy names, and Waveblaster is one of them. It's a impressive sounding name for a impressing sounding technology from Creative Labs, but in reality it's nothing but a combined MIDI- (crippled ofcourse, this is PC- technology) power- and audio-connector. The purpose of the Waveblaster-port (which is present on most/all Soundblaster-cards and -clones) is to connect a daughterboard with proper MIDI-sound. By building a Waveblaster-port yourself you can connect these cards to your ST/Falcon/whatever.
What do you need?
Point 2 will probably cause a few headaches, as the standard PSU in the (Mega)ST/Falcon doesn't have -12v. I have been informed that the TT- and MegaSTE-PSU will deliver -12v. You'll also need some space for the card, so this project is probably best suited for those of you that have recased machines with PC-powersupplies.
- A computer with a standard MIDI interface.
- A PSU that can deliver +5v, +12v and -12v.
- A piece of Veroboard or similar, some cheap parts.
- Some experience with a soldering iron.
- A Waveblaster MIDI-card.
It's also possible to convert a Waveblaster-card into a complete standalone MIDI-unit (Elektor Electronics, July/August 1997), but buying a ordinary GM/XG module is probably cheaper.
Pin-layoutThis is the layout of the Waveblaster port:
- 2,4,6,8,10,12,16,18,20,22,24,26: Ground
- 3: MIDI in
The MIDI-input is TTL, so you'll need some circuitry to convert the standard MIDI current loop to TTL.
- 14,1,7,11,15: Not connected
- 5,9,13: +5V
- 17: +12V
- 21: -12V
- 19: Audio out, right
- 23: Audio out, left
The audio-outputs are standard line-level, but can't deliver enough juice for headphones.
- 25: Reset
Reset is active low.
The complete circuitThis circuit has everything you need to connect a Waveblaster-card to your ST/Falcon. It consists of three main-parts:
- MIDI "current loop" to TTL converter
- The optocoupler IC1 with the additional parts D1, R4 and R5 converts MIDI "current loop" to TTL. This is cruical, I tried several solutions before I resigned and ordered myself some optocouplers.
- Buffer and MIDI-THRU
- IC2 buffers the converted TTL-signal before it's fed to the Waveblaster-port, as well as providing a MIDI-THRU together with R2 and R3. MIDI-THRU must be used as your machine's new MIDI OUT if you need one.
- R1/C6 resets the card at power-up. You could replace C6 with a switch and reset manually, but I wouldn't recommend that as the card can easily be reset by software if needed.
Click on the circuit to download a larger version.
- R1 - 10KOhm
R2, R3, R4 - 220Ohm
R5 - 1k8Ohm
C6 - 10uF/25V
C7 - 100nF
D1 - 1N4148
IC1 - CNY17-2 (I've used a CNY17-3)
IC2 - 74HCT00
Some connectors, wires and a piece of Veroboard.
Yamaha DB50XGMy Waveblaster-card is a Yamaha DB50XG, which is rather expensive but also rather good :-) Any Waveblaster-card should work, but I have only tested the Yamaha and can't guarantee anything.
SoftwareSome useful software for XG-cards and MIDI in general.