121–130 of 130 posts
Yamaha builds so much stuff that this could have been about ... a boat ... a motorcycle ... a guitar ... or the iconic synth :-)
Also note—there’s no interpolation. Those 4096 entries in the table? That’s all you get. The chip will not interpolate between them.
This was the first thing I scanned the article for. Without interpolation, my understanding is there's likely a TON of aliasing in the raw output, but then that goes through a 16khz lowpass filter that chops everything above 16khz off - cleaning it up.
The inverting input of IC56 might be a good place.
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…
Slightly related: I really love the build quality of Yamah's 80s/90s rack synths. The physical interfaces were very well-designed, and look amazing.
Earlier quoted context omitted.
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…
I have the same problem with the TX802. I do my best to avoid the 'performance mode' features entirely. Slightly related: I really love the build quality of Yamah's 80s/90s rack synths. The physical interfaces were very well-designed, and look amazing.
Also note—there’s no interpolation. Those 4096 entries in the table? That’s all you get. The chip will not interpolate between them.
This was the first thing I scanned the article for. Without interpolation, my understanding is there's likely a TON of aliasing in the raw output, but then that goes through a 16khz lowpass filter that chops everything above 16khz off - cleaning it up.
This is not correct, unfortunately. Aliasing is a time domain artifact, affected by the sample rate. The limited table size instead causes distortion, which affects the values.
If you ever run a bitcrusher plugin, you’ll see two sliders—one for bit depth, one for sample rate. Aliasing is affected by the sample rate. This is kind of like the other slider—the distortion slider in a bitcrusher plugin. Although it is like having not one bitcrusher, but many bitcrushers, reducing every signal inside the synthesizer to about 12 bits. Kind of. The distorted signal is evaluated at some sample rate, which also introduces aliasing (in addition to the distortion).
These effects are musically quite distinct. Aliasing is not generally harmonic, distortion generally can be (if you arrange it to be so).
Earlier quoted context omitted.
The distinction that I’m making is exactly that. You can’t incorporate direct feedback into a phase modulation synthesizer, you need to incorporate delay into the feedback path. By comparison, you can use direct feedback with subtractive or FM synthesis. The one-sample delay basically turns the feedback into an iterated function system. With certain parameters, you end up with aperiodic results—cool in theory, but in…
But if we take the simplest example, f(x) = sin(x + c*f(x)), we can solve it, (numerically). If I run it up to 0.5π for c=0.5, I get something that's (obviously) very close to the function with a short delay. So I take that as the possibility of direct feedback, although in a electronic circuit, feedback also has a minute delay.
For certain values of x and c! You will end up with branch cuts for |c| > 1.
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…
Nope, just destroy it because you or your audience are knuckledraggers.
Earlier quoted context omitted.
But if we take the simplest example, f(x) = sin(x + c*f(x)), we can solve it, (numerically). If I run it up to 0.5π for c=0.5, I get something that's (obviously) very close to the function with a short delay. So I take that as the possibility of direct feedback, although in a electronic circuit, feedback also has a minute delay.
> we can solve it, (numerically) For certain values of x and c! You will end up with branch cuts for |c| > 1.
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…
And in John Chowning's original article, he bops back and forth between the two without mentioning it.
In practice, phase modulation is more useful and makes more sense. And yes, the DX-7 uses phase modulation throughout.
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With Frequency Modulation, you can have an operator feed back on itself. However... with such an arrangement it is entirely possible for it to get stuck at 0 Hz. Not very musical.
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And phase modulation makes a lot more sense. Watch as I demonstrate.
Student: "How does FM synthesis work?"
Teacher: "Well, do you know what happens if we have one oscillator modulating the frequency of another oscillator?"
Student: "You mean like vibrato?"
Teacher: "Yes, exactly. Now imagine a vibrato at the same frequency as the second oscillator."
Student: "That's doesn't even make sense."
Teacher: "Not to worry, the Bessel Functions still apply."
Student: "What's a Bessel Function. Can I calculate it?"
Teacher: "Not directly. It's kind of complicated."
Student: "Mutherfucker!"
Okay, now let's try phase modulation.
Student: "How does phase modulation work?"
Teacher: "Okay... Do you know how distortion works?"
Student: "I'm a guitar player. I'm intimately familiar with distortion."
Teacher: "Great! So distortion is a nonlinearity on the Y axis of a waveform."
Student: "Yep!"
Teacher: "Well, phase modulation is a nonlinearity on the X axis of a waveform. We stretch the waveform here [hand gesture], and compress the waveform over here [hand gesture]."
Student: "Hmm, warping the waveform along the X axis. That sounds kind of like PWM."
Teacher: "It's kind of similar, yeah."
Student: "Cool; thanks. I understand."
Earlier quoted context omitted.
The DX7ii I have is a fucking tank of a machine and I'm playing it until it breaks, fixing it, and then playing it some more. I guess I kind of understand typical "car guys" now. The best part is being able to map the sliders to /almost/ any parameter within a patch, so it's possible to have expressive control over the tonality of your instrument while playing live. Sure it involves menu diving to figure out ahead of…
Hah! You're using it like it was intended to be used, the DX-7 is first and foremost a performing musician's tool, that's exactly why it was built as strong as it was, made to be tossed in the back of the car on the way to gigs. If you ever can't find a part let me know.
Mostly though I've just got some weird dirty hiss (sounds like a rainstorm) on the output all the time that makes it unsuitable for recording. I use DEXED + midi in that case, but it's still fun on it's own (also weirdly I find menu-diving to edit patches easier than being presented with that big DEXED UI)
Thanks for keeping these things alive