Hammond Tonewheel with Audio to CV pitch

Pedalboards
#1

Hello there,

As an exercise really, I am trying to implement the various tonewheel organs as set out in this vintage article
https://www.soundonsound.com/techniques/synthesizing-tonewheel-organs-part-1

I am stuck here →

I am going to filter the sub-oscillator using the Juno's low-pass filter, with the cutoff frequency set precisely 19 semitones (one octave and a fifth) above the sub-oscillator pitch itself.

I don’t think we have an oscillator that has a built in sub right ? Ok cool I use 2 AMS VC03, with the second one pitched one octave lower, but then how do I implement its cutoff frequency as described above ? I am guessing I need the lowpass filter, setting its frequency by some calculated value inferred from the audio coming out of the oscillator, or from the cv going into it…

My best shot is to use a booster attenuator taking the same freq in, with an offset (and this is where I am not sure how to get 19 semitones), to drive the cutoff freq of a low pass filter.

Cheers!

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#2

Heya, cool project :slight_smile:

The AMS VCO and AMS VCF both respond to 1V/octave pitch signals, so you could calculate how many volts 19 semitones would be, and add that as an offset. A quick google gave me this thread that goes into that into more detail: Voltage values for 1v/oct just intonation. - MOD WIGGLER

Actually, because it is 19 semitones above the sub oscillator, this is equal to 7 semitones above the main oscillator. So you would just patch the pitch signal that feeds the main VCO3 into the VCF, and then add an offset for 7 semitones using a control to CV plugin into the VCF.

Hope that helps :slight_smile:

//Jesse

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#3

Super useful Jesse, thanks a lot :pray:

4 Likes