Quote:
Originally Posted by
EvilDragon
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The math is the same, yes. Now, it depends on the calculator which does that math. DX7 had limited CPU power and I would think that samples in it weren't calculated as 32 or 64-bit floats, which is what FM8 is doing. That's why FM8 sounds "cleaner" and not as "grungy" - it has more precise calculations.
This. I'm pretty sure the DX7 is like the OPLx series that have been extensively reverse engnieered for very precise emulation. You're right that the FM chip is waaay too slow to do even 16-bit floating point calculations on the fly. In the YMF262 OPL3 case (kinda of a single chip child of the 81z 4-op) it uses fixed integer lookup tables for not only frequency divisions but also for sinusoid calcs. Hence it's quite rough in the maths where sin accuracy (phase) functions are quite audible.
Quite ingenious, its all just lookup tables, very fast response w/ no real cpu interaction. Remember this is 1980s tech!
I own/owned many FM synths over the years, aliasing is really audible in the older gear. My PreenFM for example has loads of aliasing which gives it this sharp edgy grit moreso than your average Yammy FM. Also I used to have one of the original brownie DX7, might be the 12-bit DAC but it sounds quite different than say a 81z on top of having a high noise floor.
Check it out, someone completely de-encapsulated a OPL3 and reversed it:
https://docs.google.com/document/d/1...1rIm42nwo/edit