From the course: Learning Modular Synthesis: Eurorack Expansion

Erica Dtech: Exploring instability

From the course: Learning Modular Synthesis: Eurorack Expansion

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Erica Dtech: Exploring instability

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(electronic music) - [Narrator] In the first movie, we found the Erica Dtech Polivoks filter to be interesting, but not quite as wild and crazy as it's reputation. The fun happens, when you start increasing the resonance slope, lets go ahead and get this to the point where we have a little bit of audible resonance here. (note resonating) You can see a little peak there around the fifth harmonic. On our spectrograph display. Now we'll start increasing the resonance slope. You can see the wave form grow. (resonating note grows louder) So the resonance peak is moving up in frequency, (resonating note grows louder) and now you here some instability start to come in. (note wavers) I can cut back the input level a little bit. (note steadies) To tame that. The input level will drive it into a more unstable response. (note wavers) Up to full Polivoks mode. (note wavering loudly) Very sensitive of that input level. Let's do slow filter sweep. (note resonating) Very pronounced as we come across those harmonics. (keyboard notes resonating) If you like instability, that's a lot of fun. If you don't like it, dial back the input level. (note steadies) (keyboard playing notes) (note grows louder and wavers) Now if you want to get even crazier, start playing with the CV assign control. That takes some of the control voltage coming in, which we're using right now to lift the cut-off frequency and also track the keyboard a little bit. And we'll start to send it to the resonance amount, increasing the amount of feedback and driving it into oscillation. When you have an envelope coming in, and you assign a little bit of that envelope's peak, or blip to the resonance, you'll get an additional amount of resonance, or feedback, or oscillation, just on the attacks. I'm going to go ahead and go toward a shorter decay there. Start pulling down the CV assign as I play notes. (keyboard playing notes) (volume increases) (electronic wavering) You can hear the more extreme resonance now. And see the display on the spectrograph go to noise during that sweep. (electronic resonating) Now it may seem very unruly when you have a slower envelope like this, (electronic resonating). But it's actually a lot of fun, when you have a very short envelope. (short rapid notes) They develop just a little bit of punch right at the start of a note. (series of short rapid notes) And the amount of craziness, is also controlled by the resonance slope. (notes steady) Going to flat gives a much more normal filter response. Going to a Polivok slope, gives you the instability. (notes resonating and wavering) Of course resonance now controls this, too. (notes steady) (wavering increases) And also input level, also affects how much instability you have. (notes waver) Particularly when we bring our second oscillator into the mix. (notes waver faster) (notes steady) And again you still have the cutoff curves dial. (volume increases) Much brighter sound. (volume decreases) More muted sound. Very obvious, the difference between one and two pull, with this filter. It's not as obvious with some other filters. (notes end) And as if it wasn't enough that the Dtech gave you all this control over how stable, unstable you get. Again basically, the more clockwise you go in resonance and resonance slope, and the more counterclockwise you go with CV assign, the more unstable you get, also higher levels make you more unstable. This does have a switch to go into a bandpass mode, as well. (keyboard playing notes) (notes begin resonating) I can start playing around with resonance (volume increases) (notes waver) (electronic resonating) You can really, on these edges of instability, if you're over-driving it. (electronic resonating) Very sensitive to input level in addition to resonance amount. (keyboard playing notes) (electronic resonating) More control voltage to resonance. More feedback, more oscilation, more instability. (note steadies) Or you could just make it a very tame filter (keyboard playing notes) So if you want something that's a bit crazier, a bit nosier, a bit wilder, a bit edgier. Go seek out what's referred to as an unstable, or so-called aggressive filter. One based on a Russian Polivoks design will get you there, but I particularly like the Erica Dtech variation, because it's an enhancement of the original Polivoks design, and gives you even more control.

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