OPL3 surround mode

By ToriHino

Hero (653)

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27-02-2018, 21:47

Apparently the OPL3 supported 4 channel surround mode, see Resound OPL3, starting at about 50 seconds.

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By Grauw

Ascended (9678)

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27-02-2018, 22:43

OPL4 has six output channels even. One for FM (DO0), one for PCM (DO1), and one for FM+PCM (DO2). For FM channels you can select to output to DO0 and/or DO2, and for PCM channels you can output to DO1 or DO2. I think the primary original purpose was to allow an YSS225 effects processor to be introduced, offering a wet/dry audio path (see OPL4 application manual pages 1, 11, 19, 52, 58, 60).

But it can also be used to output 4 or even 6-channel surround. Though it feels a little awkward to me (not designed for it), as unlike FM, the PCM part can only output to one of the outputs at a time, so you need to duplicate channels if you want to play on four speakers, and of course DO1 can not be assigned to FM nor DO0 to PCM. Also the panpot and balance settings are aimed at 2-channel output. But it can be made to work, with some extra expenses. You need to add DACs to DO0 and DO1, and for mix them for 4-channel output. Though without software support the other channels will stay silent.

On MoonSound DO0 and DO1 are not connected, so you have to output to DO2 always.

By FiXato

Scribe (1694)

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28-02-2018, 16:17

I was wondering the same after seeing LGR's video about the Resound OPL3 :)

By ToriHino

Hero (653)

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28-02-2018, 18:21

Actually LGR's video triggered me in the first place too Smile Somehow it would be nice if the MSX platform could beat the PC by being the first to produce a song using front L/R and back L/R channels in true surround sound Cool