VCO’s as Not-VCO’s

[Buttons ARE toys]

Even if your VCO doesn't go down to 0Hz, it can be a lot of fun to plug some drums into the FM input and use the VCO as a sort of distortion. Run the drums through an envelope follower and use that to envelope the osc and it can sound really punchy and dirty. Also sounds great if you mix it back in with the dry drum sound after.

[CervelloAnalogico]

No-one mentioned MI Rings? Although I'm not sure you'd call it a VCO, it's certainly a voice... and it can be a resonator.

[vidret]

Even if your VCO doesn't go down to 0Hz, it can be a lot of fun to plug some drums into the FM input and use the VCO as a sort of distortion. Run the drums through an envelope follower and use that to envelope the osc and it can sound really punchy and dirty. Also sounds great if you mix it back in with the dry drum sound after.

I run audio through the different inputs of VCO's but good shout on the envelope thing actually, gonna mess with that.

[virtualpt]

With wavetable VCOs and custom tables you can use this concept to make a quantizer, pseudo-sequencer (not really clocked but CV-addressable), comparator, logic, frequency multipliers/dividers, etc

I would love to learn a bit more about this specific concept. Are there any good things to read/watch online about it? Thanks!

I’m afraid I don’t have a lot in the way of sources but there are a couple threads here that go into it:
https://www.modwiggler.com/forum/viewtopic.php?t=23694
https://www.modwiggler.com/forum/viewto ... 9#p3783025

To try to explain a bit: a wavetable oscillator usually stores a single cycle of a wave (well usually an array of many waves, but stick to one for now) which is played back by a phase lookup.

Here’s a sine wave with phase markings from 0 to 360 degrees:
EB73478E-E3C9-4FC1-B881-AE1741846AC7.gif

The “frequency” of a wavetable VCO is the number of times for second it scans through that wavetable from 0 to 360 (one sine cycle). Modulating the “phase” will basically change the position that the scanner starts at. It offsets from 0.

[side note: with sine waves, this is the original patent for “FM synthesis” a la the DX7. It’s wavetables!]

So let’s say you slow down your frequency to 0Hz. The phase table lookup now doesn’t move at all. It just sits there at 0 degrees, which is 0 volts (or some DC offset depending on your table).

Now we put a CV into the phase modulation, and we scan through the table. We can do this as slowly as we like; since the VCO is at 0Hz, it’s not going anywhere by itself. We can go forwards or backwards, jump around, whatever.

So let’s say instead of a sine wave, you put in a staircase of voltages : 12 steps at 1/12 volt intervals. Then feed a CV into the phase lookup. Whatever the CV voltage is at, the lookup table snaps it to the 1/12 volt step below. Out comes a quantized pitch.

If you put some arbitrary other non-staircase series of steps, you can make a “sequencer”. You can put a ramp CV into phase mod and get the sequence of steps out.

If you put a 0 amplitude at zero degrees, then a step up to full amplitude at 180 degrees (halfway through), you get an on-off switch, a comparator. You can change the threshold by modifying the degree index of the “on” point.

You could make a “window comparator” by having the wavetable go from 0 to max back to 0.

Or you could make a wavetable that has two sine wave periods in it. Scanning that gives you two cycles for every 0-360, doubling the pitch.

I think the frequency divider thing is a mistake on my part. I don’t actually know how you can do that.

Anyways yeah. Hopefully that’s clear enough! (And more or less correct)

Fantastic explanation. Thank you so much for this. This is a such a clear explanation, I really appreciate it. I could never really understand the 0Hz function in my E352, despite reading several explanations. Now I get it & am looking forward to some experimentation.

[Wavtekt]

This is an interesting topic.

Let me take this topic literally and post something weird.

I found out a while ago, if I patch saw output of my Electrosmith 3340 VCO to IN input of Triple Cap Chaos, then patch y output back to back to CV input and X output to exp FM input of VCO. I can create chaotic self-FM'ed VCO that sometimes oscillating on pitch, sometimes FM'ing chaotically.

Isn't this a VCO that is not a VCO?

Get creative with feedback patching!