Tiar / SmashedTransistors Contributions

#81

Hi all,
I have a Music Thing Modular AxoControl attached to one of my Axolotis and i will develop/share some patches for it in:
menu: File -> Library -> Community -> tiar -> AxoControl

One of my goals is to get the maximum functionalities out of a very limited number of pots.

LittleClassic is the first i'm developing, and sort of test bench for ideas.
Basically it should cover most of the classic synth sounds:

Features:

  • saw/sqr waveforms
  • low pass filter with resonance and envelope
  • amplitude envelope
  • three oscillators
  • 8 different detunings for the three oscillators
  • post filter distortion
  • reverb
  • 6 voice polyphony
  • vibrato controlled by modulation wheel CC
  • volume controlled by expression CC

Ideas:

  • use left/right sides of pots as switches for options such as :
    • envelope mode ("piano" / "organ")
    • distortion on/off
    • waveform
    • reverb on/off
  • use tiar/kfunc/ objects to map multiple parameters on a single knob (sort of presets).
  • use tiar/kfunc 8 or 16 segments to make steps with smooth transitions
    • ex: Detune ratios for two oscillators
    • use blinking led as feedback to signal a transition zone between steps
  • highest attack time (full right) switches control to aftertouch
  • The release time can be common to both filter and gain envelopes
  • use aftertouch as part of sustain for envelopes in "piano" mode.

At the moment the controls are :

  • knob 1 (PA5) controls the cut-off of the filter AND distortion
    • center for minimum cut-off
    • full left or right for maximum cut-off
    • left: no distortion
    • right: distortion
  • knob 2 (PA6) controls the envelope on the filter.
    • if turned from middle to left, the envelope is a decay envelope (piano type).
    • if turned from middle to right, the envelope is an AR envelope (organ type).
    • if turned full right the filter is controlled by aftertouch (channel or poly)
  • knob 3 (PA7) controls the resonance of the filter and the waveform:
    • from left to middle : square waves
    • from right to middle : sawtooth waves
    • center for minimum resonance
    • full left or right for maximum resonance.
  • knob 4 (PA2) Detune ratios for osc2 and osc3 relative to osc1 left to right:
    • x1 x1 unison
    • x2 x3 a bit of third
    • x2 x4 octaves
    • x3 x1.5 a lot of thirds
    • x3 x4
    • x7 x4.5 metal and bells
    • x5 x4 year 2k
    • x0.75 x2.5 grungy
  • knob 5 (PA3) controls the gain envelope
    • if turned from middle to left, the envelope is a decay envelope (piano type).
    • if turned from middle to right, the envelope is an AR envelope (organ type).
    • if turned full right the gain is controlled by aftertouch (channel or poly)
  • knob 6 (PA4) controls the release for both gain and filter envelopes AND the reverb
    • center for minimum release time
    • full left for right for maximum release time.
    • left : low reverb
    • right: stronger reverb

A draft layout...

LittleClassic.png744x534 581 KB

Updates 14 jul:

  • extendend filter cut off range
  • Button A (PC1, LED PB1) controls gate effect (8 per sec)
  • Button B (PC2, LED PB8) controls pan effect (1 per sec)
  • Button C (PC3, LED PB9) switches gate to high speed (sort of ring mod).

Updates 16 jul

  • Finished a few adjustments
#82

Objects tiar/dist/SqrtMix4

try the help patch, in the editor menu bar, clic Help -> Library -> Community -> tiar ->dist -> SqrtMix4

This is a non linear "mixer".
I think it can be useful with sine inputs or combined with FM/PM. (see the help patch to get an idea).

If only one input is set, it won't be distorted. Distortion only occurs when multiple inputs are active and interfere.

Technically,
the output is the (signed) square root of the sum of inputs (signed) squares. Here "signed" means that we take the negative value of the square root or square if the input is negative. See code for details.

Note: I did not implement antialiasing with this one. Hence DP anti aliasing of a "signed square root" is certainly possible.

#83

Objects tiar/dist/DP sqrt

try the help patch, in the editor menu bar, clic Help -> Library -> Community -> tiar ->dist -> DP sqrt

It is a DP antialiased square root distortion.

UPDATE: added toggle switch to change negative output to linear. Useful for asymmetric distortion.

This kind of distortion emphasizes the low amplitude part of the waveform. Thus, the output signal crest factor is far better that the input signal crest factor. => I will develop some sort of mixer around this idea...

The negSlope parameter and inlet allow to control how the negative portion of the signal will be processed. It turns the object into a non linear wave rectifier reminiscent of some diode/resistor waveshapers.

Tech notes:
This object uses differentiated polynomial anti aliasing:

The square root is a very special case of polynomial, it is x ^ 1/2. ( " ^ " stands for "power" )
The integral of this function is 2/3 x ^ 3/2 which is 2/3 x * (x ^1/2).
The code uses the intrinsic float function arm::vsqrtf to calculate it. Even if this operation takes 14 cycles, it is quite efficient as the STMF cpu is capable to perform integer operations in parallel.

#84

Objects tiar/dist/DP inv2

try the help patch, in the editor menu bar, clic Help -> Library -> Community -> tiar ->dist -> DP inv2
and Help -> Library -> Community -> tiar ->dist -> DP inv2 and PM

This distortion is inspired by electronic circuits that use polarisation points of non linear components.

Here, I use an hyperbolic function "polarised" around 1 with a controllable "factor" (that controls the non linearities):
Low factor => almost linear, nice for modelling old amps:

Mid factor => nice dissymetric distortion

High factor => pulsy, level detector distortion

note: all graphs plotted on Wolfram Alpha

Note that gain and range are automatically modified so that this distortion takes a full range signal and outputs a full range signal. It makes it convenient when used with sine generators and Phase Modulation to add a somewhat "analog" color.
try Help -> Library -> Community -> tiar ->dist -> DP inv2 and PM

Tech note:
This distortion is antialiased by differentiation, much like the good old DP (differentiated polynomials).

Next step:
generalisation of the differentiation method to rational functions. Very nice distortions can be done with these.

#85

tiar/dist

A little word about work in progress...
I'm working on a set of DP antialiased distortions.
I will post more detailed information soon.

Some help/test patches are already available in

Help -> Library -> Community -> tiar ->dist -> ...

  • compand
    for companding (use in conjonction with expand for non linear mixers...)
  • expand
  • rectify
    a full wave rectifier.
  • step
    an "infinite gain saturation". (planned lighter CPU than the factory dist...)
  • fold
    a wave folder.
  • squares
    alternating positive and negative steps.
  • modulo
    a modulo folder (sounds harsher than the classic fold).

To my ears, the anti aliasing by analytic pre integration / numeric differentiation is good enough to allow the combination of multiple distortions in parallel and series... and maybe feedback through tuned delay lines :stuck_out_tongue_winking_eye:

#86

Hi,

I still have some work in progress... mainly porting and optimising some code to the Axoloti such as the anti aliased distortions as described in the previous post.

I'm also porting this step invariant implementation of "the" 24dB filter

Raph Levien paper: http://levien.com/ladder.pdf

With my simplifications:

The step invariant method is a "Zero Delay Feedback" method that allows deep modulation and high resonance without frequency warping (the main drawback of the now omnipresent bilinear transform filter).
One of the drawback of the step invariant method is that it can be CPU intensive.

Anyway if you want to give my first experiments a try. See
Menu bar Help -> Library -> Community -> tiar -> filters -> MgExp.axh

Question about filters
#87

That sounds great!
Really nice modelled analogue filters are something the Axoloti has lacked, thus far. Is this implementation antialiased?

a|x

#88

Hi @toneburst,

This filter does not include distortions and is not prone to aliasing.
Frequency warping (which is another form of aliasing) is prevented by the matrix exponentiation scheme (square and scale) which is equivalent to a x64 oversampling.

#89

Patch: Violin_commutedWaveguide.axp

menu: File -> Library -> Community -> tiar -> Strings -> Violin_commutedWaveguide

If you feel like you want to play the GoT theme... or Psycho... or Eleanor Rigby... well

This is a 3 voice polyphonic Violin patch based on synchronous Phase Mod (syncPM4) oscillators and feedback tuned delay lines (i'm still struggling to improve these for Karplus Strong synthesis schemes...). A simplified (and practical) version of commuted waveguide synthesis

It is especially designed for polyphonic aftertouch (it should also work with mono aftertouch).

#91

Objects tiar/osc/Qsc

try the help patch to get an idea: menu: Help -> Library -> Community -> tiar ->osc -> Qsc

This is a kind of bandlimited sawtooth oscillator capable of simulating low pass filtering and resonance with little CPU and low aliasing.

It is inspired by the trick Casio used with the CZ synths (waveforms 6, 7, 8).

#92

tiar/dist/DP type IIA and DP typeIIB

help/test patches are already available in
Help -> Library -> Community -> tiar ->dist -> DP type IIA and B
both examples are mono synths that use simple signals as inputs for the distortion.

These object use integro differential anti aliasing of rational functions (a polynomial divided by another polynomial).

I experimented with many analytically integrable rational functions and i chose those that do not have tan nor log. Here are two functions that i found quite interesting.

Here is "type II A".
the distortion function "type II A"

F2.PNG241x572 13.1 KB

Here is "type II B": is almost the same thing that type II A but with sort of crossover distortion as found in some push pull transistor amps.

Combination in series or/and parallel leads to interesting results...

#93

Patchs disto "guitar" Type IIA and Type IIB

menu: File -> Library -> Community -> tiar -> guitar -> Type IIA

heavily distorted sine wave oscillator.
The distortion consists in a series of Type IIA objects with highpass and allpass filters.

#94

Really nice, paired these up with the brds/sinefold oscillators and modulated everything subtly and slowly - loads of delightful harmonics.

I don't see the guitar/Type IIA at all in the library, however.

#95

It is in community/tiar.. maybe a problem with the library update...

#96

Patch RadioMorse

menu: File -> Library -> Community -> tiar -> synths -> RadioMorse

use and abuse of the tiar/dist/SyncAlias module to get a dirty and radioactive digital flavour (polyphonic with autopan and delay).

#97

Just synced libraries again.
Definitely not there, while the other new ones are.

#98

No RadioMorse, either.

Problem on my end or your end?

#99

Hi @blaerg,
They are in the patches, not in the objects.
They are, with many other patches in File (from the editor menu bar) -> Library -> community -> tiar -> ...

#100

Problem on my end, then! A problem in awareness - I didn't even know this patches menu was there...

#101

Another 'hidden' one is:

menu bar -> Help -> Library ->...

it directly accesses the "help patches" associated to objects