VCA with gain

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JoPo
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VCA with gain

Post by JoPo » Thu Jul 05, 2018 7:36 am

Hi ! Don't know if there are still much module designer.... :roll: But I don't understand why there is only VCA's that only atenuates the signal amplitude and none that could also increase it. That would be very useful ! For instance : building a compressor that would increase low parts volume.
Without such a VCA, if I want to build a compressor that could increase low parts volume, I must add an amplifier just before the VCA but by doing like that, if the audio signal I want to compress has peaks higher than the added gain in the amplifier, the result is cliping. And that wouldn't occur with a VCA that has also positive gain.
All amplifier modules in Scope modular have only async input to modulate their gain and async signals are really not enough time accurate for making a compressor.

Or maybe there is a way to do what I discribed without positive gain VCA ? Please, tell me ! Thank you.
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RA
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Re: VCA with gain

Post by RA » Thu Jul 05, 2018 8:09 am

Well...there is a process called parallel compression which does that. Also i think an expander can do that. A drawback of positive gain is you are also gaining up noise. Signal might go up 10db...but the noise in that signal also.

Or you can take the gr out(for metering) and substract that from a max value(sum with inverted gr?) and achieve roughly the same ;)
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garyb
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Re: VCA with gain

Post by garyb » Thu Jul 05, 2018 8:45 am

a compressor basically does that. a VCA would be the same as just normalizing the part. there is not anything that can think for you, and there is no getting something for nothing....or i probably misunderstand the request...

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Re: VCA with gain

Post by valis » Thu Jul 05, 2018 6:58 pm

I'm confused, are you saying that makeup gain isn't enough in a compressor?

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Re: VCA with gain

Post by JoPo » Fri Jul 06, 2018 11:12 am

Sorry ! Hard to be clear...

I just would like to have modular VCA that could also increase the signal amplitude at its input. All Scope modular VCA can only decrease the amplitude = they only can lower the signal.
It would be very useful (at least for me ! :D ) to sometimes increase the amplitude with a VCA. It is possible with an amplifier module but in Scope modular, in that kind of module, the gain is always modulable via async signal which are not fast and accurate enough.

If I want to increase the gain, I must use an amplifier module with a static gain, then modulate (only in lower direction) the amplitude with a VCA. The problem is that when the signal amplitude I'm modulating is closed to 0db, it cliping will occur with a static gain.

But with a VCA that can have positive gain (increase the amplitude), it can increase gain on low amplitude parts and decrease (as it already does) amplitude on loud parts of the signal.

RA --> when you build a compressor in SDK, I guess you're using a VCA to modulate the volume, amplitude of the signal you are compressing. Is your VCA able to increase the volume or only decrease ? And in that case (only decrease), how do you design the circuit (I guess with an amplifier somewhere) to obtain a louder volume as fast as a compressor can do ?

I'm aware I may be wrong ! And if anyone has the best design for a modular compressor, please, throw it away here ! :)
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Re: VCA with gain

Post by RA » Fri Jul 06, 2018 9:49 pm

Well, a comp is fairly easy in its gain structure. No matter how you build the compression section, that section attenuates the signal. After compression the signal is less. Then you can use a static gain module as the makeup part. This is how comps work.

To avoid clipping you can pre attenuate the signal and make an output gain the user can set by itself. Internally there are so much tricks gainwise you can do.

As i said, you can use math modules for some tricks. And there is a volume modulator which you can use since that can also use sync for the modulation(ofcourse).

Another way is if you want your trick on the tail of a signal one could compress the start of the signal and increase overall volume. That will do the same:
You want to increase a portion of a signal but you can also decrease the other portion and increase overall. Its basically the same.
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fra77x2
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Re: VCA with gain

Post by fra77x2 » Sat Jul 07, 2018 4:27 am

You can use a pitch modulator

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Re: VCA with gain

Post by valis » Sat Jul 07, 2018 11:50 pm

No, he just seems to be missing out on that fact that you have a post-vca 'gain' at the end of most compressors that can then bring the overall level up. By compressing the peaks and then applying post-gain, you get exactly what he *seems* to be asking for, which is a reduction in peaks and subsequent gain in the lower sections....without clipping.

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Re: VCA with gain

Post by JoPo » Sun Jul 08, 2018 8:00 am

Thank you ! I must do some test, now.... And come back here at the first little issue ! :D
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