Yamaha synthesizers MSX compatible

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Van anonymous

incognito ergo sum (116)

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24-12-2013, 09:06

FM-PAC has the first two:

In Pro Tracker (Tyfoon soft) they were called distorted waveforms iirc, maybe in Synthsaurus too, dunno).

In MB, direct access to these parameters was absent, though with a bit of a hack (and probably a bug) you could still tweak them low-level. Just 'wrap' the feedback around! Go from 0..7 and then forwards to 0 again, you've now changed these waveform bits. Logically, as there are two waveforms and two operators, the number of combinations equals 4, so there are 32 feedback values to check out.

Have you ever wondered why you couldn't exactly get the FM-PAC's hardware "synth" preset out of a Music Module? This is why - it uses the other waveform! Have you ever wondered why Micro Cabin's music somehow seems to eclipse FM-only music module songs? This is why; the extra waveform.

Van Manuel

Ascended (18794)

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24-12-2013, 10:00

What wafeform is extra compared to what?

What about wafeform 2 and 3?

Van anonymous

incognito ergo sum (116)

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24-12-2013, 10:24

The first two waveforms are used in the FM-PAC, The capped sine being the extra/'distorted' waveform. This is a diagram of another OPL-chip, so the latter two aren't relevant here. The Music Module only has a sine as operator waveform. As these extra waveforms in the FM-PAC have a richer spectrum, their sound will be slightly richer and more complex. E.g. if you use this extra waveform for the carrier, then with the modulator you can make a sound spectrum envelope going from complex to complex, whereas the Music Module can only envelope its sound from complex to a simple sine. (not taking modulator sustain levels into account, but you get the idea)

Van popolon33

Expert (85)

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26-12-2013, 10:21

actually, it's a picture of the waves in OPL2
in OPL2, you can use registers R1 and R13 to use this extra waves.
when bit 5 of R1 is "1", you can select wave with bits 0 and 1 of R13 like this :
0 : picture 1 (normal sinewave)
1 : picture 2 (half sinewave)
2 : picture 3
3 : picture 4

now for OPLL (FMPAC), I've read the datasheet and application manual and i can't find any info about this extra wave (half sinewave) nor how to access this with registers... so i'm very curious about this.

Van wolf_

Ambassador_ (9956)

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26-12-2013, 12:46

Could it be next to the feedback parameter? Because of this quirk in MB, you're probably overwriting the waves because the feedback parameter isn't treated as a 3 bits value but as a 5 bits value..

Van anonymous

incognito ergo sum (116)

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26-12-2013, 13:15

Bingo! http://map.grauw.nl/resources/sound/yamaha_ym2413_ds.pdf

Address 03 in the register map, left of the "F B" you'll see DC and DM. Those are the distorted carrier and distorted modulator, a bit that switches to the other waveform. That's perhaps where the whole fuzz comes from in discussions; why Yamaha calls them 'distorted' I dunno, technically they're just operator waveforms.

Van msd

Paragon (1472)

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26-12-2013, 13:02

some sources say the opll is based on the opl2, but it only used 2 waves. In the opl3 you be able to reproduce the opll sounds.

Van popolon33

Expert (85)

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26-12-2013, 13:56

@Wolf : now i see, i didn't notice in the YM2413 application manual (page 12) that we can flatten the negative part of the sinewave to have a rectified half-sine wave.
@msd : you can reproduce all opll sounds with opl2, no need for opl3/4

Van wolf_

Ambassador_ (9956)

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26-12-2013, 14:12

Uhm, didn't the OPL4 have 8 waveforms for each operator? If so: you can't reproduce everything the OPL2 does if it has only 4 waveforms.

Van msd

Paragon (1472)

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26-12-2013, 17:17

Yes opl3 has 8. I didn't say it has 4 did I . I know you could use the opl2 to make opll sounds, but the opl2 is not available on msx as far as I know.

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