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Side-chain gating in Eurorack?
MUFF WIGGLER Forum Index -> Eurorack Modules  
Author Side-chain gating in Eurorack?
divot
Howdy folks - looking for pointers here. I'm looking for the nicest, quickest and easiest (they always go together right?!) - way to do sidechain gating a la Drawmer DS201.

One of the things I want this for is gating low-frequency oscillators using kick drums, to fatten & tone-out kick drums. So it needs to be fast, gate to total silence, and probably given the super-low-frequency content of what I'll be gating, probably needs some attack/decay control to try and avoid clicking...

Anything that does this? I can't actually find a basic DS201 equivalent in Eurorack format. Closest thing I've seen is the Make Noise Dynamix, but it's really unclear if that's going to do it well enough for my purposes...

Any clues? thanks! It's peanut butter jelly time!

cheers,
dave
xenosapien
That´s an easy one... literally use a Gate signal, like the ones you get from most sequencers and/or MIDI-to-CV converters.

for less click you could use a vactrol based Low-pass-gate (i.e. VCA and low pass filter combined) since those tend to "slew" a tiny bit and produce less clicks.

i.e. the Make Noise LxD has a strike input, meaning you could do the gating thing with a single module.
the Dynamix can probably be used in the same way, but I don´t have that module.

(you´d have to be able to provide variable gate lenghts tailored to your needs of course)

other method would be:
gate into envelope (adjust attack/release to taste), envelope into VCA´s CV control input
"to be gated" signal into VCA input, take the gated signal from VCA out. done.
xenosapien
another double post because stupid me keeps clicking "quote" instead of "edit". >_<
brandonlogic
wmd has two modules that can do side changing well.

i have the MSCL. only 4 hp love it.



and their Compressor

starthief
Aside from dedicated compressors, there's the Bastl Dynamo -- the top section is an envelope follower with comparator, which generates a "ducking" CV for a VCA (or filter or wavefolder or whatever).
subdo
This is probably completely impractical and specific to my system but might give you some ideas other than, you know, a compressor with a side chain input.

My kick drum is the SSF Entity Bass Drum which has both an envelope and inverted envelope output. What I do is take the inverted out along with the Envelope for my bass into the Mutable Kinks logic section A and B and then use the MIN output into the VCA for the bass. Sometimes I need to add some attenuation between the Entity and Kinks but often it's perfect side chain ducking without doing anything else. If I needed attack/decay which TBH I've never done I could also put it through a slew like one channel of Maths.

Now the Entity BD is a little unusual in that it provides that envelope out (inverting it is easy enough with any number of modules). It's one of the many reasons I love the Entity BD. But you could do this with any drum source with an envelope follower. In that set up you've basically built a compressor. The threshold on the follower becomes your threshold, slew settings are your attack/decay and makeup is done on the VCA. I'm not sure how you could recreate ratio but in my mind it would be how much of the side chained source you are MINing with the signal you're side chaining.
tbecker
Actual gates and triggered envelopes are OK, but not as good as using an envelope follower to grab the sound intensity and use that for dynamic control. A channel of MATHs, DUSGMK2, MI ears, Erbeverb, Morphagene, 4MS SMRF, FUMA, or compressor modules like WMD, ect that have a dedicated SD chanel output will all work. A hp or lp filter into a MATHs gives you some control over the spectrum you will integrate which is a nice touch when you are trying to put together lets say a bass line with a full spectrum drum kit.
Stab Frenzy
divot wrote:
I can't actually find a basic DS201 equivalent in Eurorack format.

The DS201 is made up of a few sections, all of which have equivalents in Eurorack. You can then just patch them together to get the effect you want.

The input section consists of a high pass filter and a low pass filter to filter out the frequencies you don't want triggering the gate. This is quite handy when you're using the gates on a drum kit to stop them triggering from bleed, but you might not need them in a modular context. Regardless, any Eurorack filters will do the job.

The next section is an envelope follower and comparator, like in the Doepfer A-119. The comparator level control acts the same as the threshold control on the DS201, it sets the level at which the gate will open. The comparator outputs a gate signal which triggers the next section, which is an envelope. To get the same controls as the DS201 you need an AHR envelope or to run the gate signal from the comparator through a trigger to gate convertor to get your hold time, and then run that new gate signal with hold into an AR envelope. Use the attack and release times of the envelope the same as you would the attack and release times of the gate, although you'll probably have a greater range of times from a synth envelope than you would from the DS201. If you've got a Maths you can use channel 1 as the trigger to gate convertor (set rise to fastest, use fall for hold time, take gate out from EOR) and then use channel 4 as the attack and release envelope.

The last section is the actual audio path, which is a VCA. If you use something like an A-132-3 or uVCA which has a bias or offset control you can use that to set your range, but for your purpose of gating a sub from a kick you want full range and any old VCA should do the trick.

It's pretty basic once you break it down into the component parts, and once you understand how all the different bits work you can patch them together in more interesting and creative ways that you couldn't do if you just had a single-purpose gate module. thumbs up
divot
I'm super-familiar with the 201, just trying to equate exactly what I want to do into Eurorack thinking (which I'm not familiar with!)

I won't need the filters for this, so looks like to accurately do side-chain keying of a super-low frequency carrier and avoid clicks (I want to gate *on* - not duck), what I'm probably looking for is an envelope module (AR or AHR or something) to be triggered by an audio kick drum, and then output of the envelope drives the control input on a VCA module. Sounds right? (In which case may actually be way easier than I thought)
xenosapien
divot wrote:
I'm super-familiar with the 201, just trying to equate exactly what I want to do into Eurorack thinking (which I'm not familiar with!)

I won't need the filters for this, so looks like to accurately do side-chain keying of a super-low frequency carrier and avoid clicks (I want to gate *on* - not duck), what I'm probably looking for is an envelope module (AR or AHR or something) to be triggered by an audio kick drum, and then output of the envelope drives the control input on a VCA module. Sounds right? (In which case may actually be way easier than I thought)


if you want to use an audio signal, you´d want an ENVELOPE FOLLOWER instead of an envelope.

An envelope is triggered by a trigger or gate signal, not by audio directly.

a Module like Make Noise MATHS would be suited for this - put a copy of the kick audio into channel 1 or 4, set the rise and fall times and the ch1 or ch4 output attenuverter to taste and take the output of ch1 or ch4 into the CV control input of the VCA that is gating your sub signal.

Maths will create an envelope-like Signal derived from the Audio input.

(Maths will also do Attack/Decay envelopes, coincidentally. There´s a reason why everybody should have at least one of those modules razz )
pr0t0
i'm using Entity's Bass Drum duck out, with nice results. log, lin and expo curves for attack and release makes it very precise. PEG with negative polarities would also work well.
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