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VCO’s as Not-VCO’s

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merlatte
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VCO’s as Not-VCO’s

Post by merlatte »

We all know of modules that aren’t primarily VCO’s that can function as such, e.g. function generators, filters, etc.

I’m curious about the opposite: modules that are primarily VCO’s that can function as something else (excluding LFO’s because duh). The one example I can come up with is the Piston Honda mk1/2; rather than using the internal oscillator to drive the wavetables, they be driven by an external input, which can have a rather different result. Are there any others like this?
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Re: VCO’s as Not-VCO’s

Post by Sleepfc »

Cwejman VCO-2RM has a nice built in ring modulator

Frap Tools Falistri is labeled as a dual function generator but has a built in Vca (also a ring modulator), and has this amazing frequency divider section that works both with audio + cv, which is superrrr handy
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Re: VCO’s as Not-VCO’s

Post by Yes Powder »

The Metasonix R-55 can be used as a fuzz.
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Re: VCO’s as Not-VCO’s

Post by jheronymo »

I mean you mention this, but to add a bit, I believe that any VCO that can go to 0Hz (usually a result of through-zero capability) essentially becomes a waveshaper when phase modulated. So you could do something like this with an analog TZPM module as well.

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

A couple “unclassifiable” modules aren’t really VCOs but might be interesting to consider here:

Chaos modules: Joranalogue Orbit, Fritz Hypster (and others), etc. They kind of straddle the LFO/VCO divide but technically are neither. I think the audio effect is someone of a pitched noise/multiphonics vibe:
As an “LFO” it does cool shit. Also outputs 3-4 simultaneous orbiting CVs:


Auza Wave Packets is a nice digital VCO and it does some stuff that would probably otherwise require many, many utilities: envelope generators, VCO/LFO, rectifier, multiple slews, logic, crossfaders…
https://www.auzaaudio.com/
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Re: VCO’s as Not-VCO’s

Post by oldenjon »

Mmm there are lots of Swiss army knife and complex / digital modules that either can either be arranged to function like a VCO or have a VCO as a sub circuit, but if a module is marketed as a dedicated VCO it likely won't do much else. There are probably a few exceptions to that, but if its marketed as a VCO and not some multi-purpose module then it's probably just a VCO. Having said that, one exception I can think of is Joranalogue Generate 3 doubling as a noise generator.
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Re: VCO’s as Not-VCO’s

Post by merlatte »

oldenjon wrote: Thu Aug 04, 2022 11:57 am There are probably a few exceptions to that, but if its marketed as a VCO and not some multi-purpose module then it's probably just a VCO.
Totally agree, I didn’t think there’d be much fitting the criteria (but I appreciate the responses :)). I do like that the PHmk1 in my small rack can have a place in a no-input feedback patch or just be a VCO and wondered if I was missing anything else that can do that.
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Re: VCO’s as Not-VCO’s

Post by Stice »

Angle Grinder can be a filter…
Turn on. Plug in. Slew down.
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Re: VCO’s as Not-VCO’s

Post by KSS »

To put specific names on a point OP and jheronymo made.
The Wiard-Blacet Miniwave and the Digisound80 VCDO that inspired it are both capable of being noise gens, WSrs and quantizers.
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Re: VCO’s as Not-VCO’s

Post by Yes Powder »

The RK4 can be a weird filter, but then again it's marketed as a VCO/filter, so I don't know if that counts.
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Re: VCO’s as Not-VCO’s

Post by vidret »

Stice wrote: Thu Aug 04, 2022 12:32 pm Angle Grinder can be a filter…
It IS a filter!
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Re: VCO’s as Not-VCO’s

Post by Yes Powder »

vidret wrote: Thu Aug 04, 2022 1:27 pm
Stice wrote: Thu Aug 04, 2022 12:32 pm Angle Grinder can be a filter…
It IS a filter!
I think it's in the same category as the RK4, in that it's marketed as both.
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Re: VCO’s as Not-VCO’s

Post by Stice »

Yes Powder wrote: Thu Aug 04, 2022 1:33 pm
vidret wrote: Thu Aug 04, 2022 1:27 pm
Stice wrote: Thu Aug 04, 2022 12:32 pm Angle Grinder can be a filter…
It IS a filter!
I think it's in the same category as the RK4, in that it's marketed as both.
Yeah agree. And it’s kiiiiiind of a mode, of sorts, so probably doesn’t count.
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Re: VCO’s as Not-VCO’s

Post by ee_ »

It took me a while after getting into euro for the lightbulb to go off that VCOs become way more useful when you stop thinking of or trying to approach them as little synth voices and get creative using them for other things.

One thing I sometimes wonder about though that holds back experimentation at times: Is there any possibility of damaging a jack or module function by sending audio signals into one that isn’t designed to receive such? Based on the number of times I’ve seen encouragement to try audio rate manipulations on parameters you wouldn’t think to, I’m guessing not, but must stupidly admit I still don’t know the answer.
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Re: VCO’s as Not-VCO’s

Post by oldenjon »

ee_ wrote: Thu Aug 04, 2022 1:58 pm It took me a while after getting into euro for the lightbulb to go off that VCOs become way more useful when you stop thinking of or trying to approach them as little synth voices and get creative using them for other things.

One thing I sometimes wonder about though that holds back experimentation at times: Is there any possibility of damaging a jack or module function by sending audio signals into one that isn’t designed to receive such? Based on the number of times I’ve seen encouragement to try audio rate manipulations on parameters you wouldn’t think to, I’m guessing not, but must stupidly admit I still don’t know the answer.
Nah. You may not get the desired behavior because audio signals are bipolar and cv inputs are typically unipolar (e.g. audio as CV will be half-wave rectified) but sensitive inputs are generally protected against conditions that can potentially damage them.

Also, to add the conversation any filter that self-oscillates can also be considered a VCO.
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Re: VCO’s as Not-VCO’s

Post by starthief »

There's Shapeshifter with its vocoder mode. Also an analog wavefolder built in that you can patch anything else into.

In that vein, Double Helix lets you patch its folder/LPG combo independently (as well as the mod bus which can effectively be used as a VCA), and includes an independent noise source and LFO -- but the VCOs themselves are standard saw-core VCOs so I'm not sure if it counts here.

"Sample player" mode in the E352/E370 could be used as wavetable-based one-shot envelope generators, as I recall. I also seem to remember a clever wavetable used for clock multiplication using the sync input? Something like that.
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Re: VCO’s as Not-VCO’s

Post by vidret »

Stice wrote: Thu Aug 04, 2022 1:49 pm
Yes Powder wrote: Thu Aug 04, 2022 1:33 pm
vidret wrote: Thu Aug 04, 2022 1:27 pm
Stice wrote: Thu Aug 04, 2022 12:32 pm Angle Grinder can be a filter…
It IS a filter!
I think it's in the same category as the RK4, in that it's marketed as both.
Yeah agree. And it’s kiiiiiind of a mode, of sorts, so probably doesn’t count.
I think the website says quadrature VCO, but just like any well tracking filter it’s both.
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Re: VCO’s as Not-VCO’s

Post by jheronymo »

I think the basic problem is that (and I’m not the first person to point this out in this thread but I guess I can’t resist restating the obvious in my own words…) circuits which can do things that are interesting in the CV range as well as the audio range tend to not be labelled as “VCO”. They get fun names like “function generator” or “complex LFO” or “patch-programmable slope generators”, etc. Not all of these things track well, and that’s where a good old VCO shines.

I love these types of modules, to the point I tend not to stock up on VCOs unless they are designed for thing like TZFM or super stable tracking.

Other “VCO” modules are packaged together with things like wavefolders, modulation busses, etc. and a good designer (IMO) will break these out so that you can get at these other functions.

This doesn’t cover everything out there though, as mentioned: Noise/VCOs for instance. Sample players. Tube stuff which can kind of be effects. Modules which blur the filter/VCO distinction.
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Re: VCO’s as Not-VCO’s

Post by natureclubcassettes »

another Shapeshifter vote, this time for the delay. Can be externally clocked and divided to fairly long times, add CV to Mod B for infinite repeats.
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Re: VCO’s as Not-VCO’s

Post by TVNoel »

jheronymo wrote: Thu Aug 04, 2022 11:17 am
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!
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Re: VCO’s as Not-VCO’s

Post by LunaticSound »

Mungo w0!

A digital arbitrary OSC, as in plays any sample of a waveform and can also be stalled. So it becomes an arbitrary lookup table, which means you can use it like stated above.
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Re: VCO’s as Not-VCO’s

Post by jheronymo »

TVNoel wrote: Fri Aug 05, 2022 1:07 am
jheronymo wrote: Thu Aug 04, 2022 11:17 am
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
EB73478E-E3C9-4FC1-B881-AE1741846AC7.gif (26.15 KiB) Viewed 288 times
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)
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Re: VCO’s as Not-VCO’s

Post by KSS »

Well said, jheronymo. :tu:

Reading the Blacet-Wiard Miniwave manual or even the old PDF build doc for the Digisound80-21 VCDO will get into the details. These were the 'Maths' of their day. Used to be hugely desirable and talked about in great length. Low resolution had them losing their shine as better digital solutions came along, but they're still valid sound making tools and very much in the spirit of this thread.
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Re: VCO’s as Not-VCO’s

Post by KSS »

Another now 'old-school' thing is a VCO with built in dividers and amplitude mixer which also becomes a pseudo SEQ and CV source of structured modulation that can easily drift into crazy.

Blacet kind of popularized the idea in one of their modules back in the day. There was a DIY thing.. Pattern SEQ? <--The name is a little limiting as it can sound not at all like a SEQ but rather serve as a complex modulation CV source.
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Re: VCO’s as Not-VCO’s

Post by TVNoel »

jheronymo wrote: Fri Aug 05, 2022 2:48 am

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)
This is superb! Thanks very much! I have experimented with using my E352 to do phase modulation on a sine wave, but never even considered the idea of using stepped waves in this way. Thank you!
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Re: VCO’s as Not-VCO’s

Post by LunaticSound »

Any square VCO is also a clock, if it has PWM which you can squeeze into disappearance you could also use it as a trigger/rhythm generator.
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