Yamaha YM3812

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Yamaha YM3812

The Yamaha YM3812 , also known as OPL2 (OPL is an abbreviation for FM Operator Type-L ), is a sound chip or integrated circuit manufactured by the Yamaha Corporation . It was widely used in sound cards for the IBM PC , e.g. B. AdLib and Soundblaster .

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Semiconductor chip of the Yamaha YM3812 in close-up

The sound chip YM3812 (OPL2) is backwards compatible with the YM3526 (OPL1), which was used in sound cards for MSX computers. Compared to its predecessor, only three new waveforms have been added. An extended version of the OPL2, the OPL3 alias YMF262 , was used from the Soundblaster Pro 2 and further spread in its successors such as the Soundblaster 16. It supports stereo sounds and can generate up to six voices with four operators in various modes four waveforms added once. There is also the OPL4, which is downward compatible with OPL3 and OPL2, but has been expanded to include wavetable synthesis .

The circuit had 244 different registers for writing. It can output nine-part sound, each voice ("channel") generated by two oscillators. Each oscillator can produce sine waves, which can be converted into three other waveforms - the negative part of the oscillation can be muted or inverted and pseudo sawtooth oscillations ( 1 ⁄ 4 sine oscillation upwards with mute areas in between) could be generated. This unusual way of generating waveforms gives the YM3812 a distinctive sound. Each of the wave generators has its own ADSR envelope generator. Its main function of generating sounds is frequency-modulated synthesis - with one of the two oscillators per channel modulating the other.

Overview of the registers of a channel

For the entire canal

  • Main frequency (10 bit)
  • Octave (3 bit)
  • Note on / off
  • Synthesis mode (FM or simply additive)
  • Feedback (0-7, with the modulator modulating itself)

For each of the two oscillators

  • Frequency factor (can be set to 1 ⁄ 2 , 1 to 10, 12 or 15)
  • Waveform (sine, half sine, sine amount or saw sine)
  • Volume (0-63)
  • Attack, Decay, Sustain, Release (4 bits each, logarithmic)
  • Tremolo (on or off)
  • Vibrato (on or off)
  • Sustain (on or off)
  • Envelope scaling per key (on or off)
  • Volume scaling per key (0-3)

Parameters for the entire chip

  • Vibrato depth
  • Tremolo depth
  • Drum mode (uses three channels to produce five drum tones)
  • Composite Speech Mode (all operators are available at the same time; intended for speech synthesis, but was practically never used and is (the only incompatibility) not included in the OPL3)

Web links

Commons : YM3812  - Collection of Images, Videos, and Audio Files