3 ms·

Yamaha’s engineers did a whole lot with very little. I can only speak to the OPL2 as used in the original AdLib PC card (and to a much smaller extent the OPL3 i

Yamaha’s engineers did a whole lot with very little. I can only speak to the OPL2 as used in the original AdLib PC card (and to a much smaller extent the OPL3 in Sound Blasters) but IIRC all the sounds came from a lookup table of 10-bit integers representing one quarter of a sine period. Through bit shifts and addition/subtraction, out came a stream of 13-bit floating-point-ish data that the DAC converted into countless game soundtracks and sound effects. Part of the character of the sound, aside from the whole FM-with-feedback deal, was how abrupt and coarse the envelope steps were. There was no averaging or fine interpolation; just the brutality of fast integer math.

ssl-3 2y ago
Interesting. Thanks! For the longest time (over 30 years) I've thought that things like the OPL3 were analog. I had no idea that those synth things were happening in numberland.
ajxs 2y ago
Here's some more technical information about the OPL2, including some images of the decapped chip: https://yehar.com/blog/?p=665 https://yehar.com/blog/?p=665 The 4-operator FM synths that Yamaha produced from the DX100 (OPP/YM2164) onwards get that characteristic 'lo-fi' sound from the length of the log-sin table. The 4-operator chips used 256 samples for the quarter log-sin wave, whereas the DX7 had 1024 samples. As you increase the length of the sine table, the timbre gets much 'smoother'. See also: https://www.righto.com/2021/11/reverse-engineering-yamaha-dx7.html https://www.righto.com/2021/11/reverse-engineering-yamaha-dx...