What is happening with distortion/saturation beyond simple static waveshaping?

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manisnotabird
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13 Feb 2018

I also assume there's "hidden" EQs/filters on perhaps both the input and output beyond any "tone" or "bass/mid/treble" knobs. But what else?

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normen
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13 Feb 2018

Not much more. The "shape" of the "edges" make the sound of the distortion. Most distortion devices also employ a low cut or shelf because the low frequencies distort first (they're the most energy) and thus might cause too many overtones in the mid regions, muddying the sound. Then many have a "tone" knob which often is basically a bell EQ boost that defines what frequency "drives" most and thus defines most overtones.

You can call it "wave shaping" but in the analog domain it's simply voltage capping in one or the other way. Either by deliberately defining a cut voltage where the circuit diverts the rest of the voltage (e.g. diode / LED distortion) or by driving parts to the point where they can't put out more voltage and "flat out" (e.g. tubes, transistors). How exactly they behave at the "border levels" is basically defining the sound - "wave shaping". Those "edges" are the overtones.

Image

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manisnotabird
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13 Feb 2018

Digital delays with "analog" modes have long sounded very good to me, as good as my real analog guitar pedals, but distortion effects seem much more "digital" to me, and the ones that sound the best come at a fairly large CPU hit and have only come out more recently (I still haven't heard anything that sounds as good as my old black Sovtek Big Muff). If it was mostly simple wave-shaping and a little bit of filter-and-EQing, you'd think this would be easy on the CPU?

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aeox
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13 Feb 2018

manisnotabird wrote:
13 Feb 2018
Digital delays with "analog" modes have long sounded very good to me, as good as my real analog guitar pedals, but distortion effects seem much more "digital" to me, and the ones that sound the best come at a fairly large CPU hit and have only come out more recently (I still haven't heard anything that sounds as good as my old black Sovtek Big Muff). If it was mostly simple wave-shaping and a little bit of filter-and-EQing, you'd think this would be easy on the CPU?
I think they use oversampling

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O1B
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13 Feb 2018

Norman's pic is spot on - imo.
I believe it is the quantization of those overtones that makes for the digital sound. Electricity In analog wiring leads to much better, less harsh, random transients.

Almost impossible to find 'analog' distortion in software once you get used to 'old hardware weight'.

There are a few: Permut8 is a distortion beast, analog or digital!
In reason, I thought the Line 6 Bass had potential. Haven't softtubed.

I've pretty much given up on software distortion,

manisnotabird wrote:
13 Feb 2018
Digital delays with "analog" modes have long sounded very good to me, as good as my real analog guitar pedals, but distortion effects seem much more "digital" to me, and the ones that sound the best come at a fairly large CPU hit and have only come out more recently (I still haven't heard anything that sounds as good as my old black Sovtek Big Muff). If it was mostly simple wave-shaping and a little bit of filter-and-EQing, you'd think this would be easy on the CPU?

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manisnotabird
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13 Feb 2018

Is all the differences between all the different distortion/saturation/fuzz plug-in's all down to post-and-pre-EQ/filtering, the exact waveform transform function (how many interesting ones can there be?) and how many times oversampled it is?

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normen
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14 Feb 2018

manisnotabird wrote:
13 Feb 2018
Digital delays with "analog" modes have long sounded very good to me, as good as my real analog guitar pedals, but distortion effects seem much more "digital" to me, and the ones that sound the best come at a fairly large CPU hit and have only come out more recently (I still haven't heard anything that sounds as good as my old black Sovtek Big Muff). If it was mostly simple wave-shaping and a little bit of filter-and-EQing, you'd think this would be easy on the CPU?
Yes, for a long time distortion created digitally sounded awful. That was because of aliasing.

The thing is this „dent“ might represent a frequency that is above Nyquist (e.g. above 22kHz at 44.1kHz sample rate). The algorithm that creates that „dent“ can‘t really know if it does while modifying the wave in the time domain (i.e. like in the picture above). But the data set (i.e. the 44.1k samples per second) cannot represent this kind of frequency at all, when stored in there it will „look like“ a lower frequency.

Image

As others said, this problem is mostly solved by oversampling. That is you simply make your data set be able to represent higher frequencies so they‘re properly stored (not as low frequency waves) and then before playing them out you use a filter to cut them off and play the audible parte below 20kHz without aliasing.
manisnotabird wrote:
13 Feb 2018
Is all the differences between all the different distortion/saturation/fuzz plug-in's all down to post-and-pre-EQ/filtering, the exact waveform transform function (how many interesting ones can there be?) and how many times oversampled it is?
How many can there be?? :) Minute changes in the „dent“ are a whole spectrum of new frequencies. Imagine you „flattening out“ the part that was there before (i.e. the sine wave). What would be left over is the new added frequencies. And from looking at waveforms you also see that things that look very similar can be completely different words or voices right? :)
Last edited by normen on 14 Feb 2018, edited 1 time in total.

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manisnotabird
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14 Feb 2018

What's a „dent“ ?

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normen
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14 Feb 2018

manisnotabird wrote:
14 Feb 2018
What's a „dent“ ?
In the first image the moment where the wvae goes from blue to red or yellow, i.e. the exact moment where the wave is „shaped“.

EdGrip
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14 Feb 2018

Also, a Big Muff (or any other distortion pedal) is a guitar-specific circuit with multiple diode clipping stages and multiple gain stages, a very unique tone control that's always active and lots of other filtering and shaping components.
Most "saturation" plugins are designed for use on mix channels or whole mixes, so they're usually much simpler and more subtle things, often designed to replicate the saturation of an analogue mixing desk or that kind of thing.

For guitar pedal distortion, I've found the Kuassa REs to be the best - although I haven't tried Positive Grid yet. Give them a look. There's a Big Muff model in their Fuzz device, but
- There are lots of different Big Muff circuits, and
- It'll never be the same as plugging your guitar into an actual Big Muff (try out both the High-Z/"Instrument" input AND the normal input on your audio interface, see which gives the best sound with the plugin active, or use a booster pedal or a DI box between your guitar and the interface.)

If you've got an interface with enough I/O, you have the luxury of running Reason channels through an actual Big Muff - again you might need to experiment with inserting something between the interface and the Big Muff input to sort out any impedance matching problems. (I haven't got an interface that could do this so I'm just speculating).

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normen
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14 Feb 2018

EdGrip wrote:
14 Feb 2018
Also, a Big Muff (or any other distortion pedal) is a guitar-specific circuit with multiple diode clipping stages and multiple gain stages, a very unique tone control that's always active and lots of other filtering and shaping components.
Most "saturation" plugins are designed for use on mix channels or whole mixes, so they're usually much simpler and more subtle things, often designed to replicate the saturation of an analogue mixing desk or that kind of thing.

For guitar pedal distortion, I've found the Kuassa REs to be the best - although I haven't tried Positive Grid yet. Give them a look. There's a Big Muff model in their Fuzz device, but
- There are lots of different Big Muff circuits, and
- It'll never be the same as plugging your guitar into an actual Big Muff (try out both the High-Z/"Instrument" input AND the normal input on your audio interface, see which gives the best sound with the plugin active, or use a booster pedal or a DI box between your guitar and the interface.)

If you've got an interface with enough I/O, you have the luxury of running Reason channels through an actual Big Muff - again you might need to experiment with inserting something between the interface and the Big Muff input to sort out any impedance matching problems. (I haven't got an interface that could do this so I'm just speculating).
But effectively those „saturation stages“ are the „wave shaping“. i.e. if you have a soft and hard clip in a cascade then the wave will be shaped differently.

And what you said about guitar plugging - it‘s the impedance matching issue. You simply get additional distortion when you put a high impedance output (guitar) into a low impedance input (mic amp, line input) because the low impedance draws so much current from the supplying circuit, causing it to break down, i.e. „dent the waves“.

EdGrip
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14 Feb 2018

I'd never "made the connection" in my brain about low input impedance and current draw!

The high-Z input is likely always going to be best for guitar, I was just suggesting trying the line input as anything is worth a try.

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normen
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14 Feb 2018

EdGrip wrote:
14 Feb 2018
I'd never "made the connection" in my brain about low input impedance and current draw!

The high-Z input is likely always going to be best for guitar, I was just suggesting trying the line input as anything is worth a try.
Mhm, you always want a ratio of at least 1:11 in terms of impedance to get a proper transmission. And a guitar pickup has a very high impedance to begin with (50kOhm+)

It‘s also the reason why many people regard old mics and preamps as „magic“. Becaus it was hard to make a high input impedance for preamps and a low output impedance for mics they all dwell just around the limit and consequently different (old) mics DO sound different with different (old) preamps - simply because you go in and out of the specs :)

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