# Reverse engineering the Yamaha DX7



## rogierhofboer (Feb 7, 2022)

Officially this does not belong on this forum, but I think some of you might find these blog posts by Ken Shirriff interesting:

Part 1








Reverse-engineering the Yamaha DX7 synthesizer's sound chip from die photos


The Yamaha DX7 digital synthesizer was released in 1983 and became "one of the most important advances in the history of modern popular mu...




www.righto.com





Part 2








The Yamaha DX7 synthesizer's clever exponential circuit, reverse-engineered


The Yamaha DX7 digital synthesizer was released in 1983 and became extremely popular, defining the sound of 1980s pop music. Because micro...




www.righto.com





Part 3








Yamaha DX7 reverse-engineering, part III: Inside the log-sine ROM


The Yamaha DX7 digital synthesizer (1983) was the classic synthesizer for 1980s pop music. It used two custom digital chips to generate so...




www.righto.com





Part 4








Yamaha DX7 chip reverse-engineering, part 4: how algorithms are implemented


The Yamaha DX7 digital synthesizer (1983) was the classic synthesizer in 1980s pop music. It uses two custom digital chips to generate sou...




www.righto.com





Part 5








Yamaha DX7 chip reverse-engineering, part V: the output circuitry


The Yamaha DX7 digital synthesizer (1983) was the classic synthesizer in 1980s pop music. It uses a technique called FM synthesis to produ...




www.righto.com





Part 6








Yamaha DX7 chip reverse-engineering, part 6: the control registers


The Yamaha DX7 digital synthesizer (1983) was the classic synthesizer in 1980s pop music. It uses a technique called FM synthesis to produ...




www.righto.com


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## doctoremmet (Feb 7, 2022)

Highly appreciate this! Thanks for posting.


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## rogierhofboer (Apr 17, 2022)

https://github.com/probonopd/MiniDexed use a Raspberry Pi to emulate a ‘DX7’


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## vitocorleone123 (Apr 18, 2022)

Plogue OPS7 = the same sound as a DX7 on your computer.


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## kgdrum (Apr 19, 2022)

vitocorleone123 said:


> Plogue OPS7 = the same sound as a DX7 on your computer.


I really don’t know much of anything about the DX7 technically or how to program it like someone that actually knows what they are doing 😱
But I absolutely love the sound of Plogue’s OPS7 it really sounds great to my ears,it’s definitely one of my favorite synth acquisitions over the holidays.


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## doctoremmet (Apr 19, 2022)

It does sound exactly like the real deal. Arturia’s DX7 is also very good to be honest. FM is an acquired taste and the DX7’s implementation of it is pretty lo-fi which only adds to the fun I guess. There was a time (basically decades) when people wouldn’t touch a DX with a ten foot pole, lol. Happy to see some love again these days.

I am so going to build a Pi based DX hehe.


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## kgdrum (Apr 19, 2022)

Back in the 80’s I bought a TX81Z,honestly I couldn’t even begin to figure it out lol
They were really inexpensive but definitely not the easiest synth to understand.


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## b_elliott (Apr 19, 2022)

If you are part of the crowd (me) who heard the FM term '_operator_' then defined it as "a fancy word for an oscillator" you would be 100% incorrect. 

It took this video _Operators and Algorithms_ to quickly clear up that bit of nonsense. For fun:









SynthBits: FM Synthesis Video by madFame


madFame is a YouTube channel featuring some great videos on FM Synthesis. We'll be reposting on YamahaSynth.com. Check out the first video here.




www.yamahasynth.com


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## doctoremmet (Apr 19, 2022)

kgdrum said:


> Back in the 80’s I bought a TX81Z,honestly I couldn’t even begin to figure it out lol
> They were really inexpensive but definitely not the easiest synth to understand.


Great synth!


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## tressie5 (Apr 19, 2022)

My TX81Z was my third synth after a Korg DW8000 and Casio FZ-1. My recording desk was a Tascam 388, everything sync'd up with a JL Cooper PPS-100. Ahh...the good ol' days.


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## doctoremmet (Apr 19, 2022)

tressie5 said:


> Casio FZ-1


Nice!


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## Pier (Apr 19, 2022)

doctoremmet said:


> going to build a Pi based DX hehe


Didn't you own a DX7?


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## Nico5 (Apr 19, 2022)

I still have my DX7 complete with the aftermarket E! card that made the MIDI better, made it possible to have 320 patches in the machine (without cartridges) and more


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## Marcus Millfield (Apr 19, 2022)

doctoremmet said:


> Great synth!


If this was GS, I'd call you a slettebak 😘

Lovely collection Doc!


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## doctoremmet (Apr 19, 2022)

Pier said:


> Didn't you own a DX7?


Multiple. Plus two TF1s and a TX802.


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## Henu (Apr 20, 2022)

I still suffer from horrible traumas caused by the DX7.

My father bought it in the mid 80's for his projects and controlling sequencers, and I remember fooling around a lot with it back then for fun. He passed away in 1989 and the synth was just laying around for a couple of years in our storage because I was still 10-11 years old and too young to do anything "proper" with it.

When I started to do music more seriously in the mid- 90's or so, that synth was the only thing I could get my hands on. And I wanted to have pianos, basses, strings, and so forth. Not that fucking buzzy digital shit reminding of broken toys than actual instruments!!! I struggled some years with that and it almost killed my enthusiasm on synths completely. You coudn't do shit with that- especially black metal and jazz/ prog stuff which I wanted! I remember having to go to gigs with that thing, feeling like shit when I saw other people using Korgs and Rolands with proper sounds, me trying my best to play anything with that piece of junk. I was 17, played in an actively gigging funk/jazz band at the time....using a freaking DX7 for basic keyboard and piano stuff. The horrors still haunt me to this very day after 25 years.

When I graduated from high school in '98, my parents informed all my relatives that I'm raising money for a proper synth. They got me a used Korg N364, and the memory of them carrying it from the car and me seeing it for the first time still brings tears in my eyes. I still use to this date and love it. It's been in hundreds of gigs, tens of studio sessions, various European tours, survived a car crash, and basically is responsible for the beginning of my whole career. The DX7 is now in my carage instead of my parents' and I think the last time I dug it up from it's case was ten years ago when I wanted to see if there was any moist inside the case. I hated that thing with passion, and still start shivering every time I hear FM synthesis used.

Oh, but the keys or DX7 are really good. Other than that, that traumatic crap can burn in a dumpster fire for all that I care.


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## NekujaK (Apr 20, 2022)

A DX7 IIFD with E! modification was my first, and only, hardware synth. I bought it back in 1987, and for about 3 years it was the backbone of my makeshift MIDI recording setup. The E! mod enabled the playing of multiple tracks simultaneously thru different MIDI channels, so using a sequencer on my trusty old Mac SE30 (with a whopping 80MB hard drive!), I was able to create multitrack arrangements on the DX7. Guitars and vocals were recorded to a 4-track cassette.

It was a pretty primitive setup, but it's how I cut my teeth on multitrack recording. Years later, I was overjoyed when soft synths started to appear and happily ditched all the hardware. Except for guitars, I'm just not a hardware guy - I love the convenience, affordability, and flexibility that the virtual domain offers, and have no desire to re-live the past...


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## Superabbit (May 2, 2022)

Henu said:


> that traumatic crap can burn in a dumpster fire for all that I care


Man, that is vivid. You hate the DX7 with the fire of a thousand suns. I kinda don't like them either. I was 21 when they came out, the music lab at USC got one hot off the line and I got a chance to play with it and it sounded uh-MAY-zing. At first. Then I realized that programming it was next to impossible (for me at least) and a big PITA with the little LCD screen and those membrane buttons. That was the first red flag. Then as the decade progressed, it turned out that nobody else could figure out how to program them either, but they sure used the hell out of the uh-MAY-zing presets on every brain-dead overproduced puff-pop song and idiotic tired sitcom soundtrack to come out of LA.

I came to loathe the DX7 "Rhodes" patch so much that it colored my appreciation of actual Rhodes pianos.

The long-term chilling effect it had on the synth industry is still with us in some ways. For a couple of decades, synth manufacturers decided that nobody actually wanted to program the things, so they all turned into these black or silver knobless slabs. When the Yamaha CS6X came out in 1999 with its knobs and ribbon controller(!), I bought one straightaway. Now of course, there are a ton of nice little synths bristling with knobs.

Yamaha's use of the term "C3" to refer to the note that is middle C on the keyboard is still confusing things, because half of the rest of the MIDI world uses the Roland/Scientific Notation convention that says that middle C is "C4." They did that because the DX7 had a 61-key keyboard, and middle C was the third C from the left on the board.

Initially wanting something then having it turn out to be an instrument of crap is a potent recipe for contempt toward the thing. In your case it was being forced by circumstances to use an instrument that wasn't up to current standards. That is another potent recipe, as you expressed quite eloquently.

Trent Reznor and I are about the same age. I used to like Nine Inch Nails, but after I saw a TV performance of them doing "Pigs," and he kicked his DX7 off the stand and stomped it into pieces, I _loved_ Nine Inch Nails.

(You don't want to get me started on Roland JC-120 amps, which also emerged from Satan's taint around that time)


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## HCMarkus (May 2, 2022)

I loved my DX7.

A pain to program, for sure but, for a gigging musician, the answer to prayers. With its velocity-sensitive keyboard and the resulting playability, I was able to leave the Rhodes at home, thus preserving what remained of my car's interior upholstery. And the way FM responded to velocity was truly wonderful for percussive sounds... not just modulating a filter like so many other synths. Yamaha's inclusion of the BC-1 Breath Controller opened up a world for me; I still love using BC today with the TEControl units.

I had an RX11, too. It sucked, but still provided my drums for a lot of the smaller live gigs. It was the RX, which used the same data cartridge as the DX, that inspired a small-scale enterprise engaged in by my brother in law Chris and me.

To make it through a gig, I needed more pattern storage than the RX11 provided. Looking into Yamaha's EEPROM-based single-bank memory cartridges, priced at $135, Chris and I were inspired to design and manufacture a four-bank cartridge, the Fourplay DataCartridge, which we sold for $100 through Keyboard Magazine and various retailers across the USA. We used the same approach to storage as the DX7 did internally, Static RAM with a battery backup, which was a lot less expensive than EEPROMs at the time. Our biggest customer was West LA Music, which sold hundreds of the cartridges. Like Guitar Center, West LA initially declined to sell our cartridge because it had a battery. But when the EEPROM-based competition (which hit the market quite a while after we did) had a reported 40% failure rate, West LA took us on and did really well for us. And out cartridge was a very reliable; less than 0.5% failure rate, so they and their customers were happy.

A true cottage business, our cartridges were manufactured by a husband/wife team in their garage in Lomita, CA. They machined a slot the bottom of an off-the-shelf small plastic case (intended for potting electronics), soldered on the components and inserted the custom PC Board thru the slot cushioned by a small rubber band, then glued on the stamped-vinyl lid. The back of the box got the Fourplay label silk screened on (the art for the label was derived from a dot-matrix printout provided by the original 128k Macintosh computer) and delivered to us for shipping.

As I recall, my DX7 got a workout loading patches into the cartridges before shipping. We had to modify our approach after getting a cease and desist letter from Bo Tomlynson, as he claimed some of the patches we we including with the cartridge were derived from his work. I have no idea if we infringed, and this was back in the day when the question of copyright for patch data had yet to be litigated, but we sure didn't want to be involved in establishing legal precedent.

My DX7 left this planet in 2003 when wildfire took my studio to the ground. But today, Arturia's version of the DX7 works great and is Apple Silicon native (unlike NI's FM8, which isn't working for me within Digital Performer.) I still love FM for certain things. I use an FM Horn with BC for my live shows; it works much better than sample-based horns in that context. Responsive plucked and percussive patches allow FM to shine. It can provide a really cool transit attack when combined with other forms of synthesis. Definitely still worth exploring!


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