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chipsynth PortaFM is a new virtual instrument emulating Yamaha FM PortaSound keyboards of the mid 80's. This video explains how I test its YM2413 (OPLL) emulation code against hardware live though analog captures. (The OPLL has an internal Time-division multiplexed 9-bit DAC)
0:00:00 Yamaha's OPLL FM chip range
0:01:29 Primer: homebrew Famicom-style hardware vs software emulation
0:02:55 Comparison: OPLL vs OPL2 chip
0:04:48 Why emulate aliasing?
0:05:10 PortaFM's Drum mode
0:05:54 How to judge emulation quality?
0:08:02 Tremolo steps
Main product page:
plogue.com/products/chipsynth...
You can also read the manual here:
s3.amazonaws.com/chipsynth/Po...
Music used:
toycompany.bandcamp.com/track...
Notes:
1)My hardware OPLL-based Famicom cartridge has an active low pass filter to keep its op-amp from going crazy, so that explains why the top end is slightly duller on hardware. This is not a flaw of the emulator. The emulator does not filter anything to match any specific OPLL-using circuit.
2)Lagrange Point (the last cartridge shown) is a 1991 Japanese exclusive Famicom game which uses the VRC7 mapper for sound purposes. This special chip, made by Yamaha (but Konami branded), has a slightly modified OPLL core inside.
3)My "chipsynth FC" hardware synth is not yet ready to show/explain fully yet, it will be around time its plugin counterpart is shipping.
4)The "tremolo steps" test: The host emu and the external chip are driven by separate master clocks and have not be reset at the same time. So their LFOs phases - which derive from that master clock are not obviously not hard-synched. So if you actually look closely, the red and green lines will eventually do the same patterns, just not at the same time.
Great PortaFM walkthough video from @cuckoomusic
• Chipsynth PortaFM by P...