Hi there,

I am trying to reasonably emulate a bitcrushing/downsampling/waveshaping guitar pedal. After having put together those three functions, I realised (looking at videos on the net - I don't actually owe the pedal) that when bit depth/samplerate are set to maximum (best sound 'quality') and a 'unitary' wavetable is used (doesn't modify anything in the sound), the actual pedal still provides a broad "distortion/fuzz" sound. (of course the video provides clean and effected sound, ensuring comprehension)

As the sound I actually get with my patch is deceiving yet logical, I came to the conclusion that the clipping stage has to be 'upgraded'. I replaced the previous [clip~ -1 1] with a [tanh~], and I found it interesting but still far from satisfactory.

Googling about analog fuzz/distortion/overdrive gave some hints, but I'm still far from being able to put together a 'simplified physical model' of such a fuzz/distortion.
So I will try to start with a good transistor electronics book, to see what is the difference between germanium and silicium devices, and see if I could use some caracteristic curves to build a [diode~] and a [transitor_amplifier~] objects.

Any help appreciated !

Thanks,

Nau

Hi,

as I was 'porting' my disto patch to Max/msp, I had to figure out what permutation and sign rules could change Puredata biquad filter coefficients into Max/msp [biquad~] coefficients. I found these rules comparing coeffcients given by the excellent [filtercoeff.mmb] made by Maelstorm to those calculated by a 'classic' [filtergraph~] in Max/Msp.

Here are two patches allowing to make this conversion in one direction or the other.

Nau

http://www.pdpatchrepo.info/hurleur/msp2pd_filtercoeffs.pd

@nau said:

Ok. And as I'd like to take account for other sampling rates than 44.1kHz, is it "correct" to calculate the cutoff freq. of this cheby with a simple "fc=(SR/2)-4kHz" ?

It's better to use (SR/2)*0.8, or something like that. They roll off at dB per octave, not per kHz.

I realised (looking at videos on the net - I don't actually owe the pedal) that when bit depth/samplerate are set to maximum (best sound 'quality') and a 'unitary' wavetable is used (doesn't modify anything in the sound), the actual pedal still provides a broad "distortion/fuzz" sound. (of course the video provides clean and effected sound, ensuring comprehension)

@acreil said:

@nau said:

Ok. And as I'd like to take account for other sampling rates than 44.1kHz, is it "correct" to calculate the cutoff freq. of this cheby with a simple "fc=(SR/2)-4kHz" ?

It's better to use (SR/2)*0.8, or something like that. They roll off at dB per octave, not per kHz.

Logical, indeed. Thanks

Just re-uploading the project, DistOdrive.pd is the main patch.

http://www.sendspace.com/file/phvsjt

Hi there Nau! I know this is an old thread, last post was 2 years ago! But do you still by any chance have your patch?

Hi SockPuppet,

here is the archive I think is "the one". I won't have much time to check it before next week, but if you encounter problems I'll do it.

https://www.sendspace.com/file/1tn9zk

Nau

@nau Awesome! Thank you so much!

On first glance I can see that the audio files are not working within the patch. I'm also getting the "divided by zero" error. I'll dig around and see if I can get it working!

Got it working

Cheers !

Sorry to bother you again, @nau, but, if you still have it could you please post your patch here, the sendspace link is dead

Try this, it should be one of the latest versions of it ... sorry for being a bit late.
The file to load is distodrive.pd, it's a kind of workbench allowing to compare the DS-1 and Tubescreamer sims.
Just had a quick try and got two "divide by zero" errors and crappy sound when distortion was engaged (click on pedal to toggle effect on/off), but I'm shure it's easy to fix, as it was a working version, normally
AQf-1.zip
Nau

Great, thanks a lot!