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Yamaha DX7 Technical Analysis

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Re: Yamaha DX7 Technical Analysis

#81

Post by S_A_P »

Anecdote I read on Gearspace- Nine Inch Nails used to destroy DX7s on stage during their tour. They would basically go to pawn shops in each town they played and buy up the DX7s. They were so reliable that they typically didnt have to worry about whether or not they worked, and the keyboard was great for playing and controlling other things via midi. They sold in such numbers that they were ubiquitous, but kinda sad to know that many were destroyed unnecessarily...

https://gearspace.com/board/electronic-music-instruments-and...

check post #34 from Charlie Clouser who toured with them in that era and is also a pretty well known producer/engineer

Re: Yamaha DX7 Technical Analysis

#82

Post by mikewarot »

The numerically controlled oscillator (NCO) aka Direct Digital Synthesizer (DDS) at the heart of this is one of the most elegant things I've encountered. I once used an NCO to adjust for belt speed variation in a machine that applied hot glue to corrugated boxes in a production environment. The CPU I had at the time was constrained to 512 Bytes of EEPROM to store the program in, and it (the NCO) really helped fit that along with all the I/O to read the input thumbwheels into the thing.

The customer kept adding features, and when I was all done, I had all the code in 511 bytes.

All a phase accumulator is is a long register you add to, and only take the top N bits off of. It's quite easy to have 64 bits of frequency resolution, regardless of how many bits your SINE table lookup is going to the DAC.

Re: Yamaha DX7 Technical Analysis

#83

Post by weatherlight »

tekstar wrote: post #74
weatherlight wrote: post #61

I was under the impression that, despite the name, the Yamaha FM synths didn't actually use frequency Modulation but rather phase modulation. With Frequency modulation you can't have an operator feed back on its self. If you take a DX7 patch and implement it on something like the PreenFM2 or PreenFM3 (which uses actual FM), any algorithm with more than a few operators is going to sound quite different. I still love t…

Woah! Are the drums also TX81Z? That sounds great!

TX81z sampled and trigger with an elektron rytm mk2. also, thanks!

Re: Yamaha DX7 Technical Analysis

#85

Post by nobleach »

nkozyra wrote: post #59
jacquesm wrote: post #5

Earlier quoted context omitted.

I repair them to keep them in play, impossible to get some of the parts so I tend to use one that is too far gone to repair a number (usually three or so) of others and then I still end up with some more spares that might come in handy later. They are incredibly durable, one that I got had been in a fire but it still worked, even though more than half of the keyboard had been burned off. The mainboard went on to repa…

In the 90s, when FM was considered inherently uncool, the DX7 was the keyboard du jour to use as a controller and subsequently smash to pieces in live sets for industrial, ebm, techno. They were dirt cheap and as mentioned, insanely solid. Same thing happened to to the Casio CZ line. I bought one at a time they were very undesirable for $75 and they now go for $500+ There's a financial lesson in here somewhere

The only problem with using it as a controller (The original DX7) was that their MIDI implementation was incomplete. So you only got velocity values of 0-100 instead of 0-127. It still has a wonderful key-bed. I've owned a couple of 'em.

Re: Yamaha DX7 Technical Analysis

#86

Post by Zenst »

nkozyra wrote: post #59
jacquesm wrote: post #5

Earlier quoted context omitted.

I repair them to keep them in play, impossible to get some of the parts so I tend to use one that is too far gone to repair a number (usually three or so) of others and then I still end up with some more spares that might come in handy later. They are incredibly durable, one that I got had been in a fire but it still worked, even though more than half of the keyboard had been burned off. The mainboard went on to repa…

In the 90s, when FM was considered inherently uncool, the DX7 was the keyboard du jour to use as a controller and subsequently smash to pieces in live sets for industrial, ebm, techno. They were dirt cheap and as mentioned, insanely solid. Same thing happened to to the Casio CZ line. I bought one at a time they were very undesirable for $75 and they now go for $500+ There's a financial lesson in here somewhere

I had a CZ101 in the day, preferred the sound from PD synthesis as it was better at base sounds IMHO.

That and the DX7 was used to death and more so - 99% just used the pre-sets and got to stage that you could name the sound they used on a sound and all got cliché.

Re: Yamaha DX7 Technical Analysis

#87

Post by tgv »

klodolph wrote: post #63
weatherlight wrote: post #61

I was under the impression that, despite the name, the Yamaha FM synths didn't actually use frequency Modulation but rather phase modulation. With Frequency modulation you can't have an operator feed back on its self. If you take a DX7 patch and implement it on something like the PreenFM2 or PreenFM3 (which uses actual FM), any algorithm with more than a few operators is going to sound quite different. I still love t…

> I was under the impression that, despite the name, the Yamaha FM synths didn't actually use frequency Modulation but rather phase modulation. With Frequency modulation you can't have an operator feed back on its self. It’s true that it’s phase modulation, but phase is just the derivative of frequency, and the derivative is a linear operator (essentially a 6dB/oct EQ). So I don’t think it’s an especially important p…

I think direct feedback in PM is possible, at least for low modulation indices. The Yamaha implementation is in software, so a one sample delay is the easiest implementation (otherwise you'd have to solve a rather complex equation at every step).

Re: Yamaha DX7 Technical Analysis

#88

Post by weatherlight »

klodolph wrote: post #76
weatherlight wrote: post #65

Earlier quoted context omitted.

One thing that is different in the preenfm2 compared to the Yamahas stuff is, that it uses linear FM and therefore will not do operator feedback. The guy behind the preenfm2 says, that feedback is not that important, when you have a variety of waveforms for modulation. Linear FM also has the advantage of being a bit "friendlier/warmer" when using complex waveforms as modulators (Higher harmonics of the modulator will…

I will say—my personal experience, in dissecting DX7 presets, is that feedback is not really used that much. If you are porting DX7 sounds to a different architecture, you can remove the feedback and replace it with something like a noise source, or another operator, much of the time, or even remove it altogether. This is just my personal experience. I often dig through DX7 patches in order to reimplement them for de…

if you try to control the parameters on the TX81z while its receiving midi info, it starts to "skip" and the notes start to lag, lol.

I wish i had a TX802 or a fs1r yamaha. Those are so nice!

Re: Yamaha DX7 Technical Analysis

#89

Post by tgv »

z5h wrote: post #71
tgv wrote: post #4

Plogue, a Canadian software company, have recently released a (software) emulation of the DX-7 in excruciating detail. Here you can see part of the trouble they went through: https://www.youtube.com/watch?v=XJ97iXQrqzw . Suffice to say that they used a logic analyzer to discover gritty details that no other analysis of the DX-7 I know has ever paid attention of.

I like to think I’m a synth nerd in the know, and certainly chat a lot and read synth forums. But Plogue have flown under my radar. This looks like great stuff at a good price. Do you own any of their soft synths?

I have two of their sample players (one for Garritan products, and their free sfz player), I've got Bidule (which is a semi-modular environment where you can combine processing units and plugins in complex graphs; a bit like Reaktor), and recently bought the OPS7, because it sounds so damn authentic and is fun to play with: it has two layers, so you get something similar to the DX-1/5 sound.

Re: Yamaha DX7 Technical Analysis

#90

Post by jacquesm »

mikewarot wrote: post #82

The numerically controlled oscillator (NCO) aka Direct Digital Synthesizer (DDS) at the heart of this is one of the most elegant things I've encountered. I once used an NCO to adjust for belt speed variation in a machine that applied hot glue to corrugated boxes in a production environment. The CPU I had at the time was constrained to 512 Bytes of EEPROM to store the program in, and it (the NCO) really helped fit tha…

> I had all the code in 511 bytes

What a waste ;)

It's funny how this works though: customer makes yet another request, at first your response is 'forget it'. Then, late at night when the house is quiet you really start to think about it and bit by bit the solution starts to present itself. Then a highly annoying bout of code golf later you manage to squeeze the feature in, and end up with more free space than you had before...

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