Three Sisters - Quality knob and usage

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soundslikejoe
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Three Sisters - Quality knob and usage

Post by soundslikejoe » Sun Sep 25, 2016 7:20 pm

I just picked up a Three Sisters used. There are a few demos out there, but I can't find this specific answer. How does the "Quality" knob relate to traditional Q function in filters? This seems to be more "mixer" and less resonance boost. Mix CCW and you blend the filtered sound with the unfiltered sound. Mix CW and you blend the filtered sound with the VCO that's under the hood. In the manual it says that "THREE SISTERS follows suit with a non-resonant sound pointing North (12:00), while emphasis increases turning clockwise."

I find it strange that this filter bleeds unfiltered signal at the 12:00 position. Using LOW, with Quality at 12:00, I hear the unfiltered sound at a very low volume.... this original signal seems to get louder as Quality rolls CCW. The original sound is present until Quality is closer to 3:00 when the Oscillator (self resonance) begins to take-over the signal.

I don't have much experience with many different eurorack filters.... only this and the MMG. Everything else was either software or other synths (Virus, Moog stuff, etc). But it seems odd... Is this normal for the Three Sisters? How have you used this CCW Quality in your patches?
Last edited by soundslikejoe on Mon Sep 26, 2016 5:58 am, edited 1 time in total.

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atrostor
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Re: Three Sisters - Quality knob and usage

Post by atrostor » Sun Sep 25, 2016 7:50 pm

soundslikejoe wrote:Mix CW and you blend the filtered sound with the VCO that's under the hood.
It's not a VCO under the hood, it's the filter resonating at high Q.

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Re: Three Sisters - Quality knob and usage

Post by soundslikejoe » Sun Sep 25, 2016 7:54 pm

atrostor wrote:
soundslikejoe wrote:Mix CW and you blend the filtered sound with the VCO that's under the hood.
It's not a VCO under the hood, it's the filter resonating at high Q.
Technical clarification duly noted. When inputs are unpatched and it's tracking 1v/8, it feels like a VCO to me.... but technically, I'm sure you're right.

What about that quality knob?

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Re: Three Sisters - Quality knob and usage

Post by atrostor » Sun Sep 25, 2016 8:00 pm

soundslikejoe wrote:
atrostor wrote:
soundslikejoe wrote:Mix CW and you blend the filtered sound with the VCO that's under the hood.
It's not a VCO under the hood, it's the filter resonating at high Q.
Technical clarification duly noted. When unpatched and tracking, it feels like a VCO to me.... but technically, I'm sure you're right.

What about that quality knob?
Yeah, so as you push the quality knob, you are boosting that cut-off frequency, until the the filter starts self-oscillating at that frequency. The noon to full-CW behavior pretty much displays a standard filter response that you would get from something like a Moog filter.

The noon to full-CCW behavior is a bit more tricky. It starts reversing the Q's direction (think downwards as opposed to upwards), so you get a notch-like filter response.

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