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They don't make them like that any more: the Yamaha DX7 keyboard

kevinboone.me

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Re: They don't make them like that any more: the Yamaha DX7 keyboard

#2
> And once we have sampling technology, there’s little point using computational techniques to make the once-novel sounds of earlier synthesizers: we can just sample the instruments themselves

You can't tweak the parameters of a filter envelope if it's "printed" to a sample.

You might sample a variety of different envelopes, but there's still fundamentally no way you can get the sound of the filter attack gradually increasing using samples.

Re: They don't make them like that any more: the Yamaha DX7 keyboard

#3
And if you want to hear it:

1. Download and install dexed: https://asb2m10.github.io/dexed/

2. Download and unpack https://hsjp.eu/downloads/Dexed/Dexed_cart_1.0.zip

3. In dexed, load the cartridge "Original Yamaha/DX7 ROM/ROM1A"

4. Load the preset E PIANO 1 and play some Whitney Houston

5. Load the present BASS 1 and play the intro to Danger Zone. Listen to how note velocity affects the attack!

Re: They don't make them like that any more: the Yamaha DX7 keyboard

#4
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.

Re: They don't make them like that any more: the Yamaha DX7 keyboard

#5

> And once we have sampling technology, there’s little point using computational techniques to make the once-novel sounds of earlier synthesizers: we can just sample the instruments themselves You can't tweak the parameters of a filter envelope if it's "printed" to a sample. You might sample a variety of different envelopes, but there's still fundamentally no way you can get the sound of the filter attack gradually i…

Which is part of what makes the Mellotron such an interesting instrument.

https://en.wikipedia.org/wiki/Mellotron

Re: They don't make them like that any more: the Yamaha DX7 keyboard

#7
post #5

> And once we have sampling technology, there’s little point using computational techniques to make the once-novel sounds of earlier synthesizers: we can just sample the instruments themselves You can't tweak the parameters of a filter envelope if it's "printed" to a sample. You might sample a variety of different envelopes, but there's still fundamentally no way you can get the sound of the filter attack gradually i…

Which is part of what makes the Mellotron such an interesting instrument. https://en.wikipedia.org/wiki/Mellotron

"Tuning a Mellotron doesn't." —Robert Fripp

Re: They don't make them like that any more: the Yamaha DX7 keyboard

#8
post #4

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 countl…

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.

Re: They don't make them like that any more: the Yamaha DX7 keyboard

#9
The article mentions PC sound cards, but this family of synthesizer chips was pretty common in video games overall ca. 1985-1995. They were used in Master System, Genesis, Neo Geo, Capcom CPS1/CPS2, Sega System 16, Midway Y-Unit/T-Unit, Namco System 1/2, and too many one-off Data East, Konami, and Taito boards to count.

Re: They don't make them like that any more: the Yamaha DX7 keyboard

#10
post #4

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 countl…

Here's some more technical information about the OPL2, including some images of the decapped chip: 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-dx...

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