Univibe Pitch Modulation

[spacecommandant]

I'm reposting this regarding Madbean's Harbinger 1.5 / Univibe:
I've been playing around with the various pots and trimpots and to my *imperfect* ears, in the vibrato mode, the amount the pitch is modulated is, let's say, a semitone. So, the signal warbles up and down a semitone and it seems that the Intensity knob attenuates the amount that the semitone warble is heard, but it doesn't change the amount that the pitch changes, if that makes sense. Adjusting the internal trimpots, to my ears, also don't change the amount that the pitch changes, they just alter how pronounced or audible it is.
So, my question is: am I wrong about this, and if not then what specifically could one adjust to control how 'far' the note is bent? Is there a practical way to have a knob which can expand or contract the amount of pitch bending, so as you turn it clockwise the warble increases/decreases in pitch?
I hope this was clear, thanks in advance....

[Mark Hammer]

It's not going to produce much pitch wobble/warble.  That's just how 4-stage phasers are, and the Univibe IS a 4-stage phaser, with the phase shift distributed more diffusely than a regular 4-stage phaser.

If you want proof, take any 4-stage phaser and lift one end of the resistor that mixes in clean signal so that the result is phase-shift only.  You will hear vibrato, but the pitch deviation will be modest.  Probably a little more than a Vibe, but not nearly as wacky as the majority of chorus and flanger pedals can achieve.

[spacecommandant]

Okay, thanks. Do you think there would be a simple/practical way to implement something like a pot to adjust from full-range to subtle vibrato? I suppose replacing the resistor you mentioned with a pot could do it, if I understand correctly? On the schematic (not sure if I'm allowed to post it) it looks like it's a 100k resistor (R15) just before the Chorus/Vibe switch.

[ElectricDruid]

The pitch shift will also depend on the LFO frequency. Faster is more pitch shift. That happens because "frequency" is a way of saying "rate of change of phase over time", and the faster the phase changes, the higher the frequency. So if we phase shift the signal more quickly, we introduce a bigger frequency shift than if we do it slowly.

[spacecommandant]

Good to know, thank you.