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Why VCA's have no EOA / EOD Triggers ???
MUFF WIGGLER Forum Index -> Modular Synth General Discussion Goto page 1, 2  Next [all]
Author Why VCA's have no EOA / EOD Triggers ???
PietroC
Curious to why Envelope Generators ( AD / ASD / ASDR...... ) have
End of Attack / End of Decay Triggers and VCA's do not ?

I guess since EG's do this their is no need for vca's to have this capability

Sorry if it's a dumb question but there are many many more LOL
authorless
VCA aren't generating any signal at all.
starthief
VCAs don't care what kind of control signal they get. LFOs, audio rate signals, sequences, random voltages, white noise, the pressure output of a controller, or whatever.

It's not really the VCA's job to analyze incoming control signals and produce more control signals that might not be meaningful.
wechard
Also, because a VCA is responding to signals rather than generating one, it has no way of knowing what will happen next and therefore can’t know if it is at the beginning or end of anything. If you want to trigger gates or pulses based on the VCA output being at a particular maximum or minimum value, then a comparator can be your friend...
PietroC
Ok since EG's control the VCA In ( 2 AD / 3 ASD / 4 ADSR and so on ) which i regard as different stages 2 stages / 3 stages / 4 stages

Technically then VCA's have Amplitude Stages which for me seems the same
( IE: 0 volt -> 5 V ->3.5 V -> 0 V )

volume level ( VCA )
signal level ( EG )

Ideally to me it ssems the same
Thank You authorles for your response
Navs
PietroC wrote:
Ok since EG's control the VCA In ( 2 AD / 3 ASD / 4 ADSR and so on ) which i regard as different stages 2 stages / 3 stages / 4 stages

Technically then VCA's have Amplitude Stages which for me seems the same
( IE: 0 volt -> 5 V ->3.5 V -> 0 V )

volume level ( VCA )
signal level ( EG )

Ideally to me it ssems the same
Thank You authorles for your response


This is a nice way of looking at it, but it's not the same. An envelope generates a signal/ voltage; a VCA responds to that signal/voltage.

The envelope has 'stages' but the VCA doesn't care about this. To understand, consider a situation where you open the VCA with a static voltage, a permanent 5V signal ... what stage is that? wink

Anyway, if you'd like to generate gates at different voltage levels, you might be interested in a comparator or a window comparator module. With one of these you could get a gate on rising or falling voltages based on a threshold or a window.
calaveras
It's not the silliest idea ever.
I can see that it might be cool to have comparators on the VCA to kick out a gate whenever the signal drops below a certain threshold. There used to be Expander/Gate units for audio engineering that worked like this. It's useful for ducking/keying or even drum replacement strategies. Drawmer even made one that had MIDI integrated for that purpose.

Likewise the 281, Maths and similar modules have comparators on the envelope (or mix of envelopes) to kick out EOC, EOR etc gates. I'm the kind of nerd that has a couple stand alone (DIY!) comparators. But I can see why people with no soldering gun, and a smaller case might not want such a stand alone module.
A VCA with a comparator, might be cool product.

And if Eurorack has taught me anything, it's that there are no stupid ideas. Only stupid fucking cables that aren't quite long enough.
authorless
calaveras wrote:
It's not the silliest idea ever.
I can see that it might be cool to have comparators on the VCA to kick out a gate whenever the signal drops below a certain threshold. There used to be Expander/Gate units for audio engineering that worked like this. It's useful for ducking/keying or even drum replacement strategies. Drawmer even made one that had MIDI integrated for that purpose.

Likewise the 281, Maths and similar modules have comparators on the envelope (or mix of envelopes) to kick out EOC, EOR etc gates. I'm the kind of nerd that has a couple stand alone (DIY!) comparators. But I can see why people with no soldering gun, and a smaller case might not want such a stand alone module.
A VCA with a comparator, might be cool product.

And if Eurorack has taught me anything, it's that there are no stupid ideas. Only stupid fucking cables that aren't quite long enough.


Expanders, gates, compressors, and limiters have envelope followers of some type. If you are just measuring the voltage of the VCA's output it is going to cross whatever level you pick on a comparator, as an example, 200 times a second for a 200Hz signal.
R.U.Nuts
authorless wrote:
calaveras wrote:
It's not the silliest idea ever.
I can see that it might be cool to have comparators on the VCA to kick out a gate whenever the signal drops below a certain threshold. There used to be Expander/Gate units for audio engineering that worked like this. It's useful for ducking/keying or even drum replacement strategies. Drawmer even made one that had MIDI integrated for that purpose.

Likewise the 281, Maths and similar modules have comparators on the envelope (or mix of envelopes) to kick out EOC, EOR etc gates. I'm the kind of nerd that has a couple stand alone (DIY!) comparators. But I can see why people with no soldering gun, and a smaller case might not want such a stand alone module.
A VCA with a comparator, might be cool product.

And if Eurorack has taught me anything, it's that there are no stupid ideas. Only stupid fucking cables that aren't quite long enough.


Expanders, gates, compressors, and limiters have envelope followers of some type. If you are just measuring the voltage of the VCA's output it is going to cross whatever level you pick on a comparator, as an example, 200 times a second for a 200Hz signal.

But the comparator could also measure the VCAs CV input instead of the signal output and put out a gate whenever the CV is zero volts... I guess that would be a nice add-on for a VCA module...
notmiserlouagain
R.U.Nuts wrote:
I guess that would be a nice add-on for a VCA module...

Yes, that could be useful, one of the things that are really easy to do on circuit level, but rather annoying to patch up... A Mute gate-
Joe.
R.U.Nuts wrote:

But the comparator could also measure the VCAs CV input instead of the signal output and put out a gate whenever the CV is zero volts... I guess that would be a nice add-on for a VCA module...


There is a module that will do something similar, Elby's Slope detector.

They're pretty fun, and you can setup some pretty complex conditions for triggering when you combine them with a Flip-Flop and a Gate.

calaveras
authorless wrote:
calaveras wrote:
It's not the silliest idea ever.
I can see that it might be cool to have comparators on the VCA to kick out a gate whenever the signal drops below a certain threshold. There used to be Expander/Gate units for audio engineering that worked like this. It's useful for ducking/keying or even drum replacement strategies. Drawmer even made one that had MIDI integrated for that purpose.

Likewise the 281, Maths and similar modules have comparators on the envelope (or mix of envelopes) to kick out EOC, EOR etc gates. I'm the kind of nerd that has a couple stand alone (DIY!) comparators. But I can see why people with no soldering gun, and a smaller case might not want such a stand alone module.
A VCA with a comparator, might be cool product.

And if Eurorack has taught me anything, it's that there are no stupid ideas. Only stupid fucking cables that aren't quite long enough.


Expanders, gates, compressors, and limiters have envelope followers of some type. If you are just measuring the voltage of the VCA's output it is going to cross whatever level you pick on a comparator, as an example, 200 times a second for a 200Hz signal.

actually 400 times per second.
positive going and negative going zero crossing.
There is an easy fix, you simply add a filter in the detection path that basically lowpasses the crap out of the input until it's essentially a DC voltage. From what I understand that is how some envelope followers work. I mean really just get a Doepfer A119 and put it next to a VCA. Or just get a Maths.
authorless
R.U.Nuts wrote:
authorless wrote:
calaveras wrote:
It's not the silliest idea ever.
I can see that it might be cool to have comparators on the VCA to kick out a gate whenever the signal drops below a certain threshold. There used to be Expander/Gate units for audio engineering that worked like this. It's useful for ducking/keying or even drum replacement strategies. Drawmer even made one that had MIDI integrated for that purpose.

Likewise the 281, Maths and similar modules have comparators on the envelope (or mix of envelopes) to kick out EOC, EOR etc gates. I'm the kind of nerd that has a couple stand alone (DIY!) comparators. But I can see why people with no soldering gun, and a smaller case might not want such a stand alone module.
A VCA with a comparator, might be cool product.

And if Eurorack has taught me anything, it's that there are no stupid ideas. Only stupid fucking cables that aren't quite long enough.


Expanders, gates, compressors, and limiters have envelope followers of some type. If you are just measuring the voltage of the VCA's output it is going to cross whatever level you pick on a comparator, as an example, 200 times a second for a 200Hz signal.

But the comparator could also measure the VCAs CV input instead of the signal output and put out a gate whenever the CV is zero volts... I guess that would be a nice add-on for a VCA module...


Which is why it is on the envelope instead of the VCA.
authorless
calaveras wrote:
authorless wrote:
calaveras wrote:
It's not the silliest idea ever.
I can see that it might be cool to have comparators on the VCA to kick out a gate whenever the signal drops below a certain threshold. There used to be Expander/Gate units for audio engineering that worked like this. It's useful for ducking/keying or even drum replacement strategies. Drawmer even made one that had MIDI integrated for that purpose.

Likewise the 281, Maths and similar modules have comparators on the envelope (or mix of envelopes) to kick out EOC, EOR etc gates. I'm the kind of nerd that has a couple stand alone (DIY!) comparators. But I can see why people with no soldering gun, and a smaller case might not want such a stand alone module.
A VCA with a comparator, might be cool product.

And if Eurorack has taught me anything, it's that there are no stupid ideas. Only stupid fucking cables that aren't quite long enough.


Expanders, gates, compressors, and limiters have envelope followers of some type. If you are just measuring the voltage of the VCA's output it is going to cross whatever level you pick on a comparator, as an example, 200 times a second for a 200Hz signal.

actually 400 times per second.
positive going and negative going zero crossing.
There is an easy fix, you simply add a filter in the detection path that basically lowpasses the crap out of the input until it's essentially a DC voltage. From what I understand that is how some envelope followers work. I mean really just get a Doepfer A119 and put it next to a VCA. Or just get a Maths.


A comparator only gives a high out when the input signal goes above the threshold. You would have to full-wave rectify the signal or use a window comparator with a threshold around 0v to get 400 high outs per second. It is why pulse width modulation done with a comparator is still the same frequency as the oscillator it is being derived from.

You could use a lowpass filter as a crude envelope follower if it can go into sub-audio cutoff frequencies, which is why slew limiters are usually used. They are lowpass filters designed to go into sub-audio rates. If you full-wave rectify the signal first you will have less ripple. It is why the Serge DUSG and copies (Maths, etc.) have envelope follower patch examples.
Navs
Great discussion SlayerBadger!

R.U.Nuts and notmiserlouagain, to get a gate when the VCA is 'not being CV'd', you could use a NOT gate, or digital inverter, either ready-made or patch-extracted, e.g. your End of Cycle gate.

When it's part of the envelope, this logic is not an 'add on'; it's part of the circuit, at least in designs derived from the Serge DSG (Maths etc.), i.e. behind the scenes, it's the flip-flops and comparators that make the envelope work:

http://navsmodularlab.blogspot.com/2013/09/patch-tips-26-lets-make-env elope.html
R.U.Nuts
authorless wrote:
R.U.Nuts wrote:
authorless wrote:
calaveras wrote:
It's not the silliest idea ever.
I can see that it might be cool to have comparators on the VCA to kick out a gate whenever the signal drops below a certain threshold. There used to be Expander/Gate units for audio engineering that worked like this. It's useful for ducking/keying or even drum replacement strategies. Drawmer even made one that had MIDI integrated for that purpose.

Likewise the 281, Maths and similar modules have comparators on the envelope (or mix of envelopes) to kick out EOC, EOR etc gates. I'm the kind of nerd that has a couple stand alone (DIY!) comparators. But I can see why people with no soldering gun, and a smaller case might not want such a stand alone module.
A VCA with a comparator, might be cool product.

And if Eurorack has taught me anything, it's that there are no stupid ideas. Only stupid fucking cables that aren't quite long enough.


Expanders, gates, compressors, and limiters have envelope followers of some type. If you are just measuring the voltage of the VCA's output it is going to cross whatever level you pick on a comparator, as an example, 200 times a second for a 200Hz signal.

But the comparator could also measure the VCAs CV input instead of the signal output and put out a gate whenever the CV is zero volts... I guess that would be a nice add-on for a VCA module...


Which is why it is on the envelope instead of the VCA.


Well, not all envelopes have that feature. Furthermore you obviously can apply CVs other than envelopes to a VCA or have a mix of different CVs modulating your VCA. And another nice add-on is that you would get a fixed voltage from your VCA for free if you don't modulate it at all.
authorless
R.U.Nuts wrote:
authorless wrote:
R.U.Nuts wrote:
authorless wrote:
calaveras wrote:
It's not the silliest idea ever.
I can see that it might be cool to have comparators on the VCA to kick out a gate whenever the signal drops below a certain threshold. There used to be Expander/Gate units for audio engineering that worked like this. It's useful for ducking/keying or even drum replacement strategies. Drawmer even made one that had MIDI integrated for that purpose.

Likewise the 281, Maths and similar modules have comparators on the envelope (or mix of envelopes) to kick out EOC, EOR etc gates. I'm the kind of nerd that has a couple stand alone (DIY!) comparators. But I can see why people with no soldering gun, and a smaller case might not want such a stand alone module.
A VCA with a comparator, might be cool product.

And if Eurorack has taught me anything, it's that there are no stupid ideas. Only stupid fucking cables that aren't quite long enough.


Expanders, gates, compressors, and limiters have envelope followers of some type. If you are just measuring the voltage of the VCA's output it is going to cross whatever level you pick on a comparator, as an example, 200 times a second for a 200Hz signal.

But the comparator could also measure the VCAs CV input instead of the signal output and put out a gate whenever the CV is zero volts... I guess that would be a nice add-on for a VCA module...


Which is why it is on the envelope instead of the VCA.


Well, not all envelopes have that feature. Furthermore you obviously can apply CVs other than envelopes to a VCA or have a mix of different CVs modulating your VCA. And another nice add-on is that you would get a fixed voltage from your VCA for free if you don't modulate it at all.


But then why doesn't it make more sense to have that as a standalone module? If you have it on a VCA, then why not a VCF or any other module with a CV input?

I don't understand the fixed voltage part.
mskala
PietroC wrote:
Curious to why Envelope Generators ( AD / ASD / ASDR...... ) have
End of Attack / End of Decay Triggers and VCA's do not ?


Why do cars have accelerator pedals and bathtubs do not?

More specifically to modular synthesis: a VCA is not just for applying an envelope to an audio signal. It more generally multiplies any signal by any other. The concept of an "attack" or a "decay," either of which might have an "end," is completely foreign to the VCA; it only knows voltages. So the VCA is not a natural place to detect or to do things with the end of the attack or the decay.

Just consider what happens if you feed your VCA with two audio signals instead of an oscillator and an envelope - which is a commonplace thing to do. No attacks or decays to trigger at the end of! And although it's possible to conceive of a standalone end-of-attack detector, there is no reason for that to be a VCA feature in particular. Build it into the same module with a VCA and you have two totally unrelated circuits built into one module, not a VCA with a natural extension.
R.U.Nuts
authorless wrote:
R.U.Nuts wrote:
authorless wrote:
R.U.Nuts wrote:
authorless wrote:
calaveras wrote:
It's not the silliest idea ever.
I can see that it might be cool to have comparators on the VCA to kick out a gate whenever the signal drops below a certain threshold. There used to be Expander/Gate units for audio engineering that worked like this. It's useful for ducking/keying or even drum replacement strategies. Drawmer even made one that had MIDI integrated for that purpose.

Likewise the 281, Maths and similar modules have comparators on the envelope (or mix of envelopes) to kick out EOC, EOR etc gates. I'm the kind of nerd that has a couple stand alone (DIY!) comparators. But I can see why people with no soldering gun, and a smaller case might not want such a stand alone module.
A VCA with a comparator, might be cool product.

And if Eurorack has taught me anything, it's that there are no stupid ideas. Only stupid fucking cables that aren't quite long enough.


Expanders, gates, compressors, and limiters have envelope followers of some type. If you are just measuring the voltage of the VCA's output it is going to cross whatever level you pick on a comparator, as an example, 200 times a second for a 200Hz signal.

But the comparator could also measure the VCAs CV input instead of the signal output and put out a gate whenever the CV is zero volts... I guess that would be a nice add-on for a VCA module...


Which is why it is on the envelope instead of the VCA.


Well, not all envelopes have that feature. Furthermore you obviously can apply CVs other than envelopes to a VCA or have a mix of different CVs modulating your VCA. And another nice add-on is that you would get a fixed voltage from your VCA for free if you don't modulate it at all.


But then why doesn't it make more sense to have that as a standalone module? If you have it on a VCA, then why not a VCF or any other module with a CV input?

I don't understand the fixed voltage part.


You also could call such a module "multipurpose analog/digital logic module that applies analog AND logic to inputs A nad B and derives a digital signal from input A" if that makes more sense. Either way I like the idea.

The fixed voltage is the comparator gate going high if the VCA is not in use (no modulation applied and thus a signal at the input is obsolete). Such a fixed Voltage is always handy to have...
snm
comparator. comparator comparator. comparator
PietroC
Thanks So Much for the response
Wigglers on here are really helpful

Im extremely confused about Comparators and mostly of every response that followed
I'm looking into understanding what is said Its gonna take sometime

:bang:
cptnal
Comparators are dead simple: is voltage A higher than voltage B? If yes, gate output a gate, otherwise do nothing.

Like elsewhere in modular, the simplest ideas are the most powerful... This is fun!
ndkent
One sort of end of release tactic for an envelope that has no end of release signal is basically turning 0v into a gate, which is perfect if you want a cycling envelope.

The method is you invert, so the inverted envelope is all less than 0v. Then you offset the inverterted envelope with positive voltage so it just hits the gate threshold. What I mean is an envelope or other gate utilizing module has a voltage that once past it interprets it as a gate, So with the actual envelope less than the off state, you push what was 0v up a few volts with an offset. So you get a gate (not a trigger) all the time the envelope has no voltage, perfect if you want to fire it again, though of course once you've fired it, the gate being produced stops, so your gate is always short.
Homepage Englisch
I don't quite get it. It's perhaps that I see VCA as a fundamental block. Surely, if you have a VCA with input, CV input, and output, I suppose you can have a comparator on CV input but...

It's like adding ADSR to a phaser module. Useful perhaps, even with the context of phaser. But I would expect a dedicated module.

I don't think it's silly, just unusual.
electricanada
Joe. wrote:
R.U.Nuts wrote:

But the comparator could also measure the VCAs CV input instead of the signal output and put out a gate whenever the CV is zero volts... I guess that would be a nice add-on for a VCA module...


There is a module that will do something similar, Elby's Slope detector.

They're pretty fun, and you can setup some pretty complex conditions for triggering when you combine them with a Flip-Flop and a Gate.



Ladik j-110 is a less expensive version.
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