5 ms·

Author here if anyone has questions...

by kens 5y ago

samuelous 5y ago
Just want to say that I am incredibly thankful for this series, its amazing to see how one of my favorite synths works not just in theory (FM/PM) but also on the chip level. Thanks!
backspace_ 5y ago
I feel like there was a missed opportunity with the title, why the departure from using Roman numerals and call this article part IV?
- kens 5y ago
  A missed opportunity in what way? Is "IV" better than "4"?
  - backspace_ 5y ago
    The previous article in the series used III to denote part 3. IV would be next. I guess part 5 could be titled part Five, or maybe Go since yamaha is a japanese company.
null4bl3 5y ago
Thank you for a good series of articles and some great insight into the inner working of FM synthesis in general. I have never owned one of the original Yamaha's, but i have been using the awesome Dexed VSTi plug in, that is modeled after the DX7 for several years now. And I am planning on purchasing a Korg Opsix for its FM capabilities. But for someone that has only been on the learning-by-experimenting end of FM synthesis, your articles are a great insight into the theory behind it all.
dezgeg 5y ago
How much time does reverse engineering this kind of chip take?
- kens 5y ago
  It takes a while. I got the chip on Nov 1 and have been working on it since then. (Although it's not the only thing I've been doing.) The process is a combination of taking die photos, tracing out circuitry, understanding the circuits, doing background research, and figuring out how to explain the chip in blog posts.
S_A_P 5y ago
I’ve never been a huge fan of FM synthesis as I’m mostly reminded of bad electric piano sounds that came out back in the 80s. Having owned a tx-7 I knew it was capable of more than that but then there was the whole issue of programming it that kinda sucks. That said seeing the tech and how things were implemented has me loading up the Arturia DX7-V and tinkering around with it. Have any other synths or effects on your list to look at?
- udbhavs 5y ago
  FM can be used for some incredible atmospheric pads too, like the one at this timestamp: https://youtu.be/8SDlp5jlUqc?t=416 https://youtu.be/8SDlp5jlUqc?t=416
- joezydeco 5y ago
  Once you got past the bad piano sounds, it was in way too many arcade and home video systems to keep track of: https://en.wikipedia.org/wiki/Yamaha_YM2151 https://en.wikipedia.org/wiki/Yamaha_YM2151 One of my favorite pieces is Brian Schmidt's music for Swords of Fury, a Williams pinball machine from 1988. https://www.youtube.com/watch?v=RMIp5nG-C3o https://www.youtube.com/watch?v=RMIp5nG-C3o
  - nitrogen 5y ago
    On the subject of favorite FM pieces, this 1992 track from Jill of the Jungle (rendered by one of Yamaha's OPL2 chips on a Sound Blaster) burned its way into my brain as a kid. Still a fan: https://www.youtube.com/watch?v=8pcxdYvp8uQ https://www.youtube.com/watch?v=8pcxdYvp8uQ
cesaref 5y ago
Lovely work - i'm wondering if you now have enough info to build a VHDL model from this? It would be very cool to run an emulation on an FPGA. My interest in these instruments goes back a long way - I reverse engineered my DX7 to build a VST instrument around 2001 or so. My reverse engineering was 'black box' with putting test patches and midi through the instrument to build a model, but was good enough to produce patches which I couldn't tell from the original except at very extreme settings where the different in sample rate became apparent (e.g with aliasing frequencies being very obviously different between the two). Actually, thinking about it, I also did the same with the TX instrument to produce a simple model written in SOUL a few years back. There's a LatelyBass patch here based on this - https://soul.dev/lab/?id=LatelyBass https://soul.dev/lab/?id=LatelyBass
- rasz 5y ago
  It has been done for OPL3 https://github.com/gtaylormb/opl3_fpga https://github.com/gtaylormb/opl3_fpga I have a suspicion emulating in software specific Yamaha hardware implementation would not only lead to bit perfect reproduction, but also faster emulator. I wonder how slow of an MCU would one need, 20MHz AVR? 30MHz STM32?
  - cesaref 5y ago
    Ooh, that's an interesting project, definitely lots there for me to learn about. Thanks!

Author here if anyone has questions...

by kens 5y ago

Author here if anyone has questions...

Just want to say that I am incredibly thankful for this series, its amazing to see how one of my favorite synths works not just in theory (FM/PM) but also on the chip level. Thanks!

backspace_ 5y ago

I feel like there was a missed opportunity with the title, why the departure from using Roman numerals and call this article part IV?

kens 5y ago
A missed opportunity in what way? Is "IV" better than "4"?
- backspace_ 5y ago
  The previous article in the series used III to denote part 3. IV would be next. I guess part 5 could be titled part Five, or maybe Go since yamaha is a japanese company.

null4bl3 5y ago

Thank you for a good series of articles and some great insight into the inner working of FM synthesis in general. I have never owned one of the original Yamaha's, but i have been using the awesome Dexed VSTi plug in, that is modeled after the DX7 for several years now. And I am planning on purchasing a Korg Opsix for its FM capabilities. But for someone that has only been on the learning-by-experimenting end of FM synthesis, your articles are a great insight into the theory behind it all.

dezgeg 5y ago

How much time does reverse engineering this kind of chip take?

kens 5y ago
It takes a while. I got the chip on Nov 1 and have been working on it since then. (Although it's not the only thing I've been doing.) The process is a combination of taking die photos, tracing out circuitry, understanding the circuits, doing background research, and figuring out how to explain the chip in blog posts.

S_A_P 5y ago

I’ve never been a huge fan of FM synthesis as I’m mostly reminded of bad electric piano sounds that came out back in the 80s. Having owned a tx-7 I knew it was capable of more than that but then there was the whole issue of programming it that kinda sucks. That said seeing the tech and how things were implemented has me loading up the Arturia DX7-V and tinkering around with it. Have any other synths or effects on your list to look at?

udbhavs 5y ago
FM can be used for some incredible atmospheric pads too, like the one at this timestamp: https://youtu.be/8SDlp5jlUqc?t=416 https://youtu.be/8SDlp5jlUqc?t=416
joezydeco 5y ago
Once you got past the bad piano sounds, it was in way too many arcade and home video systems to keep track of: https://en.wikipedia.org/wiki/Yamaha_YM2151 https://en.wikipedia.org/wiki/Yamaha_YM2151 One of my favorite pieces is Brian Schmidt's music for Swords of Fury, a Williams pinball machine from 1988. https://www.youtube.com/watch?v=RMIp5nG-C3o https://www.youtube.com/watch?v=RMIp5nG-C3o
- nitrogen 5y ago
  On the subject of favorite FM pieces, this 1992 track from Jill of the Jungle (rendered by one of Yamaha's OPL2 chips on a Sound Blaster) burned its way into my brain as a kid. Still a fan: https://www.youtube.com/watch?v=8pcxdYvp8uQ https://www.youtube.com/watch?v=8pcxdYvp8uQ

cesaref 5y ago

Lovely work - i'm wondering if you now have enough info to build a VHDL model from this? It would be very cool to run an emulation on an FPGA. My interest in these instruments goes back a long way - I reverse engineered my DX7 to build a VST instrument around 2001 or so. My reverse engineering was 'black box' with putting test patches and midi through the instrument to build a model, but was good enough to produce patches which I couldn't tell from the original except at very extreme settings where the different in sample rate became apparent (e.g with aliasing frequencies being very obviously different between the two). Actually, thinking about it, I also did the same with the TX instrument to produce a simple model written in SOUL a few years back. There's a LatelyBass patch here based on this - https://soul.dev/lab/?id=LatelyBass https://soul.dev/lab/?id=LatelyBass

rasz 5y ago
It has been done for OPL3 https://github.com/gtaylormb/opl3_fpga https://github.com/gtaylormb/opl3_fpga I have a suspicion emulating in software specific Yamaha hardware implementation would not only lead to bit perfect reproduction, but also faster emulator. I wonder how slow of an MCU would one need, 20MHz AVR? 30MHz STM32?
- cesaref 5y ago
  Ooh, that's an interesting project, definitely lots there for me to learn about. Thanks!