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"Slope Rectification" Method

Discussion in 'F.O.H.' started by torridgristle, Sep 6, 2019.

  1. torridgristle

    torridgristle New Metal Member

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    Recently I was experimenting with ways to morph a sine wave into a saw wave for a harmonically rich tone and have, so far, settled upon Slope Rectification.

    Typical Rectification flips the polarity of the signal when it passes through zero and becomes negative, turning a sine wave into a triangle shape of sorts.

    Slope Rectification differs by measuring the slope of the signal and flips the polarity when it slopes downward, turning a sine wave into a saw wave by flipping it at the crest of the sine.

    Here's how you do it:

    You'll need the free plugin Maths for Windows and Mac. Add it to your processing chain and paste these equations into L out and R out:

    sign(lp12(r,200,0.5)-lp12(ri1,200,0.5))*r
    sign(lp12(l,200,0.5)-lp12(li1,200,0.5))*l

    What this does is detect the slope of a signal what's been lowpassed at 200hz at 0.5 Q and from this the sign of the slope is taken, so if the slope is positive it will equal 1 and if it's negative it will equal -1. Then this is multiplied by the original signal, so if the slope is positive then the signal is unchanged but if the slope is negative then the signal is inverted. You can adjust the cutoff frequency and filter q by replacing the numbers, it ranges from 8 to 20000 hz and I recommend lowering it enough to get mostly the fundamental and some harmonics so that these base frequencies are the primary source driving the slope detection.

    Alternatively you can use:

    hp12(sign(lp12(r,200,0.5)-lp12(ri1,200,0.5))*r,10,0.5)
    hp12(sign(lp12(l,200,0.5)-lp12(li1,200,0.5))*l,10,0.5)

    What this does is it adds a highpass filter at 10hz at 0.5 Q to remove some DC offset. You can change the frequency and Q like the lowpass filter as well and use it to retain only buzzy sounds from the Slope Rectifier.

    Here's an example:
    https://cdn.discordapp.com/attachments/475089535563464727/619574647305928744/Example.mp3
    I don't play guitar so I hope the samples are alright. First it's the dry signal with the cabinet simulations, then the Slope Rectifier with the cabinet simulations, then the Slope Rectifier and EQ and allpass filter and Voxengo Boogex with the cabinet simulations.
     

    Attached Files:

  2. Genius Gone Insane

    Genius Gone Insane http://www.¯\(°_o)/¯.com

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    Very interesting. What are you using this for? Have you tried putting this through an amp? Might sound really cool.
     
  3. torridgristle

    torridgristle New Metal Member

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    I'm using it for general distortion purposes and farty bass sounds. I've tried it with an amp sim, that's what Voxengo Boogex is, but not a real amp. Low CPU usage and crunchy, at least the old one. The new one I'm not sold on.
     

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