Converting an LFO Waveform.
This circuit converts a normal Ramp/Sawtooth input with the default range of +/-5Volts, to an exponential Ramp/Sawtooth. Any offset or gain voltages are shown on the fixed value modules. This module works well with an LFO but as it stands is not suitable for use with an ADSR as it works in the -5 to + 5 V range , and not the 0 to 10V range of an ADSR.
Shown below are examples of the output waveforms. It is useful with Sine, Saw, Ramp and Triangle waveforms but not Pulse. I have used offset voltage rather than a DC blocker HP Filter on the output to make the voltages symmetrical about the 0 Volt (Y) axis, as the High Pass filter would affect the waveshape changing our LFO output once again.
Important Note: Any gain control MUST be placed preceding this module so as not to change the symmetry of the waveform around the 0 Volts axis.
Converting an ADSR Envelope.
This is slightly more complicated as we are dealing with the range of 0 to 10 Volts so we need to do some clipping to make sure the lowest output voltage is 0 Volts and to increase the output of the ED Log so we get the full 10 V range.
For this reason the Overall Level plug on the ADSR 2 module must be fixed at 10. The gain adjustment is made at the output of the prefab so we can go between -10 for inverted envelope and +10 for full normal envelope. Generating the exponential envelope just needs a Level Adjust module with the envelope feeding into both inputs.
Note: The sustain levels will be different between Linear, Exponential and Log shaping – as yet I haven’t found a way to avoid this issue. Blame the laws of mathematics!
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