Yamaha YMF278
Encyclopedia
The Yamaha YMF278B, also known as the OPL4 (OPL is an acronym for FM Operator Type-L), is a sound chip
that incorporates both sample-based synthesis
(often incorrectly called wavetable synthesis
) and FM synthesis
.
(PCM). It features:
The PCM synthesizer part accepts:
(OPL3) block; thus, it is also backwards-compatible with the YM3526
(OPL), the YM3812
(OPL2). Like the OPL3, it can operate in one of four ways:
Four-operator FM allows more complex sounds but reduces polyphony.
Eight waveforms are available for the FM synthesis:
Unlike the OPL3, which has four channels for sound output, the OPL4 features six channels.
MSX
sound card
and in Yamaha's SoundEdge sound card for IBM
PC
and compatibles.
standard (128 melody sounds, 47 percussion sounds).
For sound effects, the OPL4 can be connected to the Yamaha YSS225 effects processor (EP), which adds various sound effects.
Like all its predecessors, the OPL4 outputs audio in digital-I/O form, thus requiring an external DAC
chip. For this purpose, the Yamaha YAC513 DAC was designed.
Sound chip
A sound chip is an integrated circuit designed to produce sound . It might be doing this through digital, analog or mixed-mode electronics...
that incorporates both sample-based synthesis
Sample-based synthesis
Sample-based synthesis is a form of audio synthesis that can be contrasted to either subtractive synthesis or additive synthesis. The principal difference with sample-based synthesis is that the seed waveforms are sampled sounds or instruments instead of fundamental waveforms such as the saw waves...
(often incorrectly called wavetable synthesis
Wavetable synthesis
Wavetable synthesis is used in certain digital music synthesizers to implement a restricted form of real-time additive synthesis. The technique was first developed by Wolfgang Palm of PPG in the late 1970s and published in 1979, and has since been used as the primary synthesis method in...
) and FM synthesis
Frequency modulation synthesis
A 220 Hz carrier tone modulated by a 440 Hz modulating tone with various choices of modulation index, β. The time domain signals are illustrated above, and the corresponding spectra are shown below ....
.
Sample-based synthesis component
The sample synthesis part is based on pulse-code modulationPulse-code modulation
Pulse-code modulation is a method used to digitally represent sampled analog signals. It is the standard form for digital audio in computers and various Blu-ray, Compact Disc and DVD formats, as well as other uses such as digital telephone systems...
(PCM). It features:
- Up to 24 simultaneous sounds (voices)
- Output sampling frequency of 44.1 kHz (it can also accept 22.05-kHz samples – they are up-sampled to 44.1 kHz before output)
- Waveform data lengths of 8, 12, or 16 bitsBitA bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
- Stereo output (with a 16-level pan for each voice)
The PCM synthesizer part accepts:
- Up to 4 MBMegabyteThe megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...
of external memory for wave data - Up to 512 wave tables
- External ROMRead-only memoryRead-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
or SRAMStatic random access memoryStatic random-access memory is a type of semiconductor memory where the word static indicates that, unlike dynamic RAM , it does not need to be periodically refreshed, as SRAM uses bistable latching circuitry to store each bit...
memory. If SRAM is connected, then wave data can be downloaded from the OPL4. - Chip select signals for 128 KBKilobyteThe kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information...
, 512 KB, 1 MB, or 2 MB memory can be output.
Frequency modulation synthesis component
The FM part is essentially a YMF262Yamaha YMF262
The Yamaha YMF262, also known as the OPL3 , is an FM synthesis sound chip. It is an improved version of the Yamaha YM3812 , adding the following features:*twice as many channels...
(OPL3) block; thus, it is also backwards-compatible with the YM3526
Yamaha YM3526
The YM3526, aka OPL , is a sound chip developed by Yamaha as a low-cost nine channel, two operator FM synthesis chip. It was notably used in a Commodore 64 expansion, the Sound Expander, as well as several Arcade games, such as Bubble Bobble.A very closely related chip is the Y8950, or MSX-AUDIO,...
(OPL), the YM3812
Yamaha YM3812
The Yamaha YM3812 also known as the OPL2 is a sound chip created by Yamaha Corporation in 1985 and famous for its wide use in IBM PC-based sound cards such as the AdLib and Sound Blaster.It is backwards compatible with the OPL aka YM3526, to which it is very similar – in fact, it only adds 3 new...
(OPL2). Like the OPL3, it can operate in one of four ways:
- 18 two-operator FM channels
- 6 four-operator FM channels + 6 two-operator FM channels
- 15 two-operator FM channels + 5 FM drums
- 6 four-operator FM channels + 3 two-operator FM channels + 5 FM drums
Four-operator FM allows more complex sounds but reduces polyphony.
Eight waveforms are available for the FM synthesis:
- simple sine
- half sine
- absolute sine
- quarter sine
- alternating sine
- "camel" sine
- square
- logarithmic sawtooth
Unlike the OPL3, which has four channels for sound output, the OPL4 features six channels.
Applications
The YMF278B was used in the MoonsoundMoonsound
Moonsound was the name of a sound card released for the MSX home-computer system at the Tilburg computer fair in 1995. The name Moonsound originated from the software Moonblaster that was written for people to use this hardware plug-in synthesizer.- History :...
MSX
MSX
MSX was the name of a standardized home computer architecture in the 1980s conceived by Kazuhiko Nishi, then Vice-president at Microsoft Japan and Director at ASCII Corporation...
sound card
Sound card
A sound card is an internal computer expansion card that facilitates the input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces that use software to generate sound, as opposed to using hardware...
and in Yamaha's SoundEdge sound card for IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
PC
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
and compatibles.
Connectivity
For ROM wave data access, the Yamaha YRW801 2MB ROM chip can be connected to the OPL4. It holds approximately 330 samples, mostly 22.05-kHz 12-bit samples with some drums at 44.1 kHz. It is compatible with the General MIDIGeneral MIDI
General MIDI or GM is a standardized specification for music synthesizers that respond to MIDI messages. GM was developed by the MIDI Manufacturers Association and the Japan MIDI Standards Committee and first published in 1991...
standard (128 melody sounds, 47 percussion sounds).
For sound effects, the OPL4 can be connected to the Yamaha YSS225 effects processor (EP), which adds various sound effects.
Like all its predecessors, the OPL4 outputs audio in digital-I/O form, thus requiring an external DAC
Digital-to-analog converter
In electronics, a digital-to-analog converter is a device that converts a digital code to an analog signal . An analog-to-digital converter performs the reverse operation...
chip. For this purpose, the Yamaha YAC513 DAC was designed.