https://www.righto.com/2021/11/reverse-engineering-yamaha-dx7_28.html
The Yamaha DX7 digital synthesizer was released in 1983 and became extremely popular, defining the sound of 1980s pop music. Because microprocessors weren't fast enough in the early 1980s, the DX7 used two custom digital chips: the EGS "envelope" chip generated frequency and envelope data, which it fed to the OPS "operator" chip that generated the sound waveforms. A key part of the OPS chip is an exponential circuit, which is used for frequency calculation and envelope application. In this blog post, I examine this circuit—implemented by a ROM, shifter, and other circuitry—in detail and extract the ROM's data.
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Gearnews has an article about use of Raspberry Pi microcomputers in digital signal processing (DSP) systems, observing that digital synthesizers are essentially computers in specialized housings. In addition to the complex software, there is a lot of work in making an enclosure with useful controls and displays. Increasingly manufacturers are building their synthesizers around the Raspberry Pi:
The biggest synthesizer manufacturer to make use of the Raspberry Pi is Korg. The Japanese synth company's Wavestate, Modwave and Opsix digital synths all make use of the Raspberry Pi Compute Module. (They're in the module versions too.)
In an article on the Raspberry Pi home page, Korg's Andy Leary sites price and manufacturing scale as the main reason Korg decided on these components. He also liked that it was ready to go as is, providing CPU, RAM and storage in a single package. "That part of the work is already done," he said in the article. "It's like any other component; we don't have to lay out the board, build it and test it."
The software for each instrument is, of course, custom. The Raspberry Pi, however, generates the sound. "Not everyone understands that Raspberry Pi is actually making the sound," said Korg's Dan Philips in the same piece. "We use the CM3 because it's very powerful, which makes it possible to create deep, compelling instruments."
These used to be designed with off-the-shelf parts from Motorola and Texas Instruments. However around 20 years ago, according to a Raspberry Pi link about Korg synthesizers, Linux entered synthesizer production scene.
Previously:
(2024) Berlin's Techno Scene Added to UNESCO Cultural Heritage List
(2021) The Yamaha DX7 Synthesizer's Clever Exponential Circuit, Reverse-Engineered
(2019) Moog Brings Back its Legendary Model 10 'Compact' Modular Synth
(2014) History of the Synthesizer - 50 Years
(Score: 4, Informative) by DannyB on Monday November 29 2021, @03:56PM (11 children)
The new Yahmaha Reface DX [yamaha.com] replacement has only 4 operators. (search the page linked.) The original DX7 had 6 operators that were prewired in 32 selectable configurations.
Ah how I remember the fun times with my DX7 in 1986 which was pricey. I haven't used it in quite a few years now with the availability of modern cheap keyboards. I still have it in a nice padded rugged transport case. In excellent physical condition. Probably the battery needs replaced by now. Unfortunately, I don't do soldering at my age. (can't remember which end of a soldering iron to pick up)
Alas the DX7 had only a mono output. Modern keyboard synths have a nice stereo output.
People who can't distinguish between etymology and entomology bug me in ways I cannot put into words.
(Score: 2) by RS3 on Monday November 29 2021, @06:15PM (10 children)
A couple of years ago an EE / musician I know was asking about getting his hands on a MOS Technology 6581 "SID" [wikipedia.org] chip, and we started to wonder if anyone makes a copy. There are some copy chips but reportedly they're not as good as the real thing. Any experience, knowledge, thoughts? Did Ensoniq use the SID at all? Ever have an Ensoniq? Here's a project: emulate SID in sw.
(Score: 3, Informative) by Anonymous Coward on Monday November 29 2021, @07:15PM (3 children)
https://www.fpgasid.de/home [fpgasid.de]
(Score: 2) by RS3 on Monday November 29 2021, @08:21PM (2 children)
Thank you AC, that's pretty much what I would envision for such a project. Very cool. Bookmarked, and if I ever need a SID, I know where to get one (besides the 2 C64s I have, which I won't part out...).
(Score: 5, Funny) by driverless on Tuesday November 30 2021, @10:51AM (1 child)
I've tried the FPGA SID and I wasn't impressed. Emulating a design cut from rubylith with a craft knife by a guy wired up on Dr.Pepper at 3am and fabbed in 7um tech using silicon refined from sand hand-harvested in the Atacama desert just doesn't work on a modern FPGA, everything sounded like the dropper resistor for the ring modulator was specced about 100ohms too low, and I could actually hear the 0.5dB cut in the third-order harmonics over my monster oxygen-free cryogenically-cooled silver cable.
(Score: 0) by Anonymous Coward on Tuesday November 30 2021, @04:04PM
This is obviously an acoustic masking effect created by fold-down intermodulation due to interactions between axial room resonances and higher order harmonics. Have you considered treating your listening environment and investing in some magic pebbles? [machinadynamica.com]
(Score: 2) by looorg on Monday November 29 2021, @07:38PM (4 children)
Lots of audio players and emulators on modern machines emulate SID in software, or well play the tunes anyway and most of them sound fine. They might not be perfect but then what is. Not all SID chips sound the same either, also changes depending on if it's an NTSC or a PAL system. It's not that it's hard to find a SID, it is getting harder tho and they are starting to be somewhat expensive. Also you don't really know if you buy one if it will actually work or not or it will somewhat work, or if it will crap out tomorrow.
As noted there are a few hardware projects that emulate it, ARMSID is probably my current favorite. I have not heard about any single chip replacements tho, or anyone making new SID:s that is. It's old stock cannibalized from hopefully not working machines or the replacement boards (SwinSID, NANOSID, ARMSID, FPGASID and all their other names etc).
I don't know if you could slip one of these replacement boards into something else such as a Synthesizer, a SIDStation or some other music equipment. It's not really my area.
(Score: 2) by RS3 on Monday November 29 2021, @08:19PM (3 children)
Thank you. AC's link to FPGASID is exactly what I was envisioning, if I were to attempt such a project. It would be interesting to see what the market would be for a single chip; IE, custom design a new chip, have silicon made. I'd bet the market isn't strong enough to justify the costs. In other words, it would be a money loser, and FPGASID has much optional functionality- can emulate the many variations of SID.
(Score: 2) by looorg on Monday November 29 2021, @09:21PM (2 children)
I have not tried the FPGASID yet, mainly due to it being almost twice as expensive as the ARMSID. The ARM one can be programmed to switch between the different revisions and also if it should be pal or ntsc, and some other settings that I can't recall. My experience with it has been all good so far. I still have not tried running the in parallel so you get the stereo effect, one does left and another to run the right channel.
If you want to build your own I think it is the NANOsid where all things are availabe from gerbers to firmware, no sourcecode tho as I recall it now.
I really wish it was feasible but I don't really think there is a viable market for a new chip one. Unless someone just does it out of 8-bit love and dont care about if it is profitable or not. It might break even eventually but I would never bet on it.
https://www.retrocomp.cz/produkt?id=2 [retrocomp.cz]
(Score: 2) by RS3 on Monday November 29 2021, @10:32PM (1 child)
A (very) brief skim of FPGASID site reveals it's 2 SIDs in one, for true stereo:
https://www.fpgasid.de/specifications [fpgasid.de]
So the twice price kind of follows I guess. Yeah, it's not cheap, but considering what you get, it's a pretty good value. One of many things I like: you can use it in a C64 and program it to do extra stuff right from within the C64 (peeks and pokes and/or assy). If I was into doing that kind of thing (C64, 8-bit sound, etc.), I'd probably have to get one.
(Score: 2) by looorg on Tuesday November 30 2021, @12:58AM
That is interesting. The FPGASID is newer then the ARMSID so I had not paid it much attention considering the price. But if you want stereo you need two armsids, one left one right to get the six channel stereo. Then the price difference is a lot smaller. So if that is what you want it probably is fairly good value. If you just want the normal experience or replacement then perhaps not so much.
(Score: 0) by Anonymous Coward on Wednesday December 01 2021, @05:39PM
Yeah I had an Apple IIGS. You can probably emulate one now:
https://emulation.gametechwiki.com/index.php/Apple_IIGS_emulators#Audio_Capabilities [gametechwiki.com]
https://www.youtube.com/watch?v=V6aSnA5yv88 [youtube.com]
https://www.youtube.com/watch?v=Zwd7pGx4CfU [youtube.com]
(Score: 2, Insightful) by Anonymous Coward on Monday November 29 2021, @04:05PM (2 children)
More articles like this, please.
Thumbs up.
(Score: 0) by Anonymous Coward on Tuesday November 30 2021, @12:54AM
It also avoids all the shitpost comments here
(Score: 4, Interesting) by Rich on Wednesday December 01 2021, @12:59AM
Seconded!
I was struck with some belly bug, so I did not leave a comment when the article was hot. But as I still have an original DX-7 from when it came out, and use exponential internals with the 8-bit microprocessor controls of the analog synthesizer I build, that article was highly interesting to me.
Also, Ken Shiriff is worth a thousand YouTubers in gold, when it comes to technical content value. :)
(Score: 1, Informative) by Anonymous Coward on Wednesday December 01 2021, @05:49PM
https://www.youtube.com/watch?v=BCwn26FePAo [youtube.com]
https://www.youtube.com/watch?v=JlAAbvrtYzQ [youtube.com]
https://www.youtube.com/watch?v=YCK6SPvS0_I [youtube.com]