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Basic question about inverters and envelopes
MUFF WIGGLER Forum Index -> Modular Synth General Discussion  
Author Basic question about inverters and envelopes
Batlikecreature
Hi, thanks for taking the time to read this.

I'm seeking to make a synth duck a kick drum. I'm talking eurorack, in case it makes a difference.

The Percussion module I'm waiting on outputs an attack/decay envelope.

If I get an inverter, could I send that signal to a vca on the synth and have that do the trick? Or would I need to trigger a separate envelope?

I guess I'm asking about the impact of an inverter creating a negative cv. Does a vca respond to negative voltage?
Graham Hinton
Batlikecreature wrote:

I guess I'm asking about the impact of an inverter creating a negative cv. Does a vca respond to negative voltage?


All control inputs respond to the total algebraic sum of their CVs, which may include negative voltages. If a particular input only responds to positive voltages then the CV needs an offset. This can be either a front panel control knob or a dc voltage added to it. To reverse an envelope of amplitude A you need to subtract it from a constant voltage A, for ducking you may not want the full amplitude of the envelope as that would be more like gating.
Batlikecreature
Thanks. I cant say I entirely understand your answer, but I think I may get an ADSR rather than an inverter first up.
Graham Hinton
Batlikecreature wrote:
I cant say I entirely understand your answer, but I think I may get an ADSR rather than an inverter first up.


For ducking you need both.

For enveloping some VCAs have no level control knob (which just adds to the CV internally) so you just control it with an envelope voltage and it goes from off to on and back again to off.

Gain is proportional to Venv.

For ducking you need the VCA to be normally on and the envelope to reduce it. So you either need a VCA with a control knob to turn it on and a means to invert the envelope so that it subtracts from that setting or you need to add a constant DC voltage externally. Whether you need an inverter or not depends on if that function is built in to your modules. Some EGs have complimentary outputs or attenuvertor level controls.

Gain is proportional to (1 - Venv) rather than just -Venv.
moremagic
Batlikecreature wrote:
Thanks. I cant say I entirely understand your answer, but I think I may get an ADSR rather than an inverter first up.
get maths Miley Cyrus

its cliché because its true, its a stupendously deep modupe because its a mixer paired with eg's, which is what imo sets it apart from the dusg and all the other clones, including mn function


you get a full range output for each function generator, and an attenuvertor that you can use for the mix or another individual output, which would help easily witth what your doing here. you could use maths ch 1 to make the kick with the full range out, then invert it and mix it with other cvs (such as the ch 4 function generator) and send to a vca to get the ducking effect on whatever signal the vca passes
PrimateSynthesis
Batlikecreature wrote:
I'm seeking to make a synth duck a kick drum. I'm talking eurorack, in case it makes a difference.


But does sduck want to be kick drum? hihi

Anyway, you might also consider doing it with outboard. As you might get better results by having two different envelopes (one controlling the VCA making the kick; the other derived from that sound, with the advantages of key filtering and timing controls, controlling the ducking). This way you can have a sharp attack on your kick, while having the synth ducked by the bass rather than the beater.
Batlikecreature
moremagic wrote:
get maths


Hm, I think as I don't fully understand a single answer I've been given here, that I'm better served with individual modules so I can do some learning before tackling a beast like Maths.
moremagic
Batlikecreature wrote:
moremagic wrote:
get maths


Hm, I think as I don't fully understand a single answer I've been given here, that I'm better served with individual modules so I can do some learning before tackling a beast like Maths.

heres a demonstration
its way easier to use maths because you can mix the cvs within the module instead of getting another module, but it could be done with more modules

(sorry i couldnt get the instagram vid to show up even after taking the s off http)

go read the maths manual. if you cant put into words exactly why you dont need a maths for your system, you probably need one and just dont know it yet Miley Cyrus
zaphod betamax
Are there any CV inverters out there that don't invert the sign
of the voltage.

For example, imagine I am inputing a sawtooth CV with +5,0V
but want the output to be a ramp with +5, 0V.
Navs
Then you need to invert and offset.
diophantine
zaphod betamax wrote:
Are there any CV inverters out there that don't invert the sign
of the voltage.

For example, imagine I am inputing a sawtooth CV with +5,0V
but want the output to be a ramp with +5, 0V.

Are you looking in a specific format?
As suggested, a voltage processor that allows inversion and offset will get you there.

Some systems, like Buchla, only allow positive CVs... early modules like the 156 CV Processor allowed a CV signal to be inverted with respect to the system's CV range (0-15V), so basically if you sent a 1V signal into it you could get a 14V signal out. Presumably some of the modern Buchla 200e processors provide similar functionality.

I don't know if that functionality exists in other formats. I could imagine it being a nifty utility module in Eurorack, with an input, an output, and a pot for dialing in the max voltage level desired.

BTW, this was one of the nice things about the Blacet EG1, which produces a 0-10V envelope as well as an inverted envelope that is 10-0V... as opposed to the typical 0 to -10V envelope.
zaphod betamax
At present I am researching getting into modular,
so I am asking questions before I assemble one.


Thanks

diophantine wrote:
zaphod betamax wrote:
Are there any CV inverters out there that don't invert the sign
of the voltage.

For example, imagine I am inputing a sawtooth CV with +5,0V
but want the output to be a ramp with +5, 0V.

Are you looking in a specific format?
As suggested, a voltage processor that allows inversion and offset will get you there.

Some systems, like Buchla, only allow positive CVs... early modules like the 156 CV Processor allowed a CV signal to be inverted with respect to the system's CV range (0-15V), so basically if you sent a 1V signal into it you could get a 14V signal out. Presumably some of the modern Buchla 200e processors provide similar functionality.

I don't know if that functionality exists in other formats. I could imagine it being a nifty utility module in Eurorack, with an input, an output, and a pot for dialing in the max voltage level desired.

BTW, this was one of the nice things about the Blacet EG1, which produces a 0-10V envelope as well as an inverted envelope that is 10-0V... as opposed to the typical 0 to -10V envelope.
authorless
zaphod betamax wrote:
Are there any CV inverters out there that don't invert the sign
of the voltage.

For example, imagine I am inputing a sawtooth CV with +5,0V
but want the output to be a ramp with +5, 0V.


Not all envelopes or unipolar control voltages have the same max voltage, and the max voltage would determine the required voltage offset needed after inversion.
jorg
Doepfer A-140 ADSR has an inverted output in addition to the standard one.
Blairio
You could run the audio of your kick drum through an envelope follower such as MI Ears, and run the inverted output of that into a VCA.

Or use side-band compression? I don't have a eurorack compressor, but I guess there are some, and maybe even one that offers side-band compression.
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