Univibe Pitch Modulation

Discussion regarding early stompbox technology: 1960-1975 Please keep discussion focused and contribute what info you have...
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spacecommandant
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Post by 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....

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lolbou
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Post by lolbou »

I think of it as the doppler effect with a honking car driving at constant speed. The pitch is altered depending on how fast the car is coming towards you (higher pitch), or how fast it goes away from you (lower pitch). Now if the car goes back and forth, (assuming it can make an instantaneous U turn) you would get your up/down altered pitch.

If you want higher/lower pitch, you need to increase the car speed.

Changing the LFO frequency (= adjusting the speed knob) should alter the pitch : a higher speed (higher frequency for the LFO) would mean a bigger pitch difference, a lower speed (lower LFO frequency) would mean a lower pitch difference (the played note being the "neutral" pitch).

Back to the car. If you want constant pitch variation , you need a constant speed (back and forth around you). But changing the car frequency (around you) with these two constant parameters would imply changing the distance at which it performs it U-turn, i.e. changing the LFO amplitude in the Univibe.If you want the car to be twice as frequent, it has to travel half the distance : half amplitude for your LFO wave at twice the frequency...

Although a lower amplitude would mean a thin sounding vibrato effect...

That's the way my understanding and I "feel" this. Feel free to correct...
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