Make Noise QPAS: Quad Peak Animation System


This is somewhat of a personal plug, but for anyone who owns the QMMG or other multiple filters and aches for the single-source control that QPAS has to offer, may I humbly suggest you look at the ADDAC306 control module (which I collaborated on with Andre from ADDAC System).

One single CV input will allow you to control up to 5 parameters on your filter. That way you can move bands, change resonances etc, with one control (hands-on or CV). Just something to keep in mind to help you tame that GAS. It’s modular after all - lots of ways to achieve things.


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The QPAS doesn’t track 1v/oct, for several reasons:

  1. The existence of the Radiate controls would basically make this impossible since they go in multiple directions.

  2. The character of the stereo imaging is directly related to the particular expo response, as detailed in Tony’s dev story on the website:

the effect is heightened when the filter has an exponential response and the cutoff is modulated. At lower cutoff frequencies the two channels appear to move at similar velocities, but as the cutoff frequency increases, one channel will smoothly increase in velocity, becoming brighter faster. The other channel lags behind, but eventually reaches the same velocity, and finally at high cutoff frequencies the two channels coalesce into full brightness.

Yes, 1v/oct is expo response, but the design goal for this filter is to emphasize the animated character of filter sweeps, and that was therefore the empasis during development.

  1. The filters, by design, do not self-oscillate. In many cases volt per octave tracking on a filter is a way to sort of use it as a VCO, which is not so relevant here. This also plays into the choice of tailored response curve vs 1/octave.


Yeah, I keep getting the comparison but I don’t agree with it. Cold Mac is as far from becoming obsolete by the appearance of ADDAC306 as Frames is. I’d be weary to downplay Cold Mac to filter controller usage. Plus it would be very hard if not impossible to set it up so that your frequency bands move in a specified way, whereas with 306 you can have the move how you want. Not sure if the comparison is really necessary, apart from the centralized control concept (which is far from new).


Oh and regarding the two FREQ CV inputs: 1 has attenuverter, 2 is unity, and they are summed with the offset from the panel control.


Thank you for the clarification. Given that QPAS doesn’t track per se, how far can you get in terms of melodic pinging with the expo input?


Hmm, I hadn’t thought about lack of 1V/OCT tracking. That seems unfortunate given how I often want bandpass filters to track parallel to their input frequency (which seems especially relevant with a multi-peak filter that can ring for some time like this one does, and ping so nicely). It’s not a deal-breaker, but a mild disappointment.


I find pinging it so enjoyable that I almost wish I had two QPAS, one for filtering and one for pinging. I get Subotnick-esque sequences even more easily than I do with DPO and Optomix.


@ParanormalPatroler: The 306 looks brilliantly useful and I think it’d be great neighbors with a Cold Mac rather than a replacement.

@ those who tagged me inappropriate: My post was meta-commentary, not a dig. Leaving it unedited for posterity. Don’t know why a “you posted in the wrong neighborhood” joke is inappropriate but I rarely strike that sort of nerve so I’ll trust you guys on this one?

@ QPAS: We want mid-side processed demos!


I can’t wrap my head around this… does this mean the two channels (L+R) are scaled to track frequency/cutoff differently on the FREQ control (so one channel appears to ‘lag’ behind the other)?


It means that the same change in value in the modulating signal has a greater effect at higher frequencies, which is also a good verbal descriptor of the term “exponential”.

The most well-known exponential curve for synthesis is the volt per octave standard for pitch, which mimics the way the human ear hears pitch: in order to be perceived as a change of one octave, the frequency must double, regardless of the frequency range that is being heard. For example a change from 100 to 200Hz (a difference of 100Hz) is perceived as the same amount of change as a change from 1000 to 2000Hz (ten times the difference).

In the case of the QPAS the curve is tailored so that changes in frequency are even apparently “faster” in higher frequency ranges. So if two peaks are far from each other in frequency, a single modulation seems to affect the higher frequency peak more strongly than the lower frequency one. As they approach their highest frequencies this apparent modulation depth closes together somewhat.

The short version of this is simply to say that if these filters tracked 1 volt per octave, it would in fact result in a compromise to the sound of the complex modulation that is possible from simple inputs. The lack of 1v/oct tracking could even be said to be one of the reasons that the QPAS sounds so good.


Thank you for the detailed response, most appreciated!

It sounds like a lot of thought has gone into getting the most movement and interest out of the minimum of controls :+1:


Something tells me this is going to be a lot of fun patching feedback with Cold Mac, given that the crossfader and min/max can be used in stereo, and given you’ll most often have 3 pairs of filter outputs left to pay around with. I’m already planning patches…


Here’s how I’m planning on amending my Shared System to accommodate QPAS. The concept here is that the system would have three distinct voices, each producing its own stereo image, mixed and preserved into a final stereo signal at the output.

  1. Mangrove --> QPAS --> Chronoblob 2
  2. Mangrove --> Erbe-Verb
  3. Sample / System --> Morphagene

Really excited to think about a system I’ve loved for so long in a totally new way.


I gotta say, when I saw the first few demos I wasn’t really interested since the emphasis was on really watery, fast LFO into cutoff kind of sounds - I’m more into really slow sweeps (I post labradford songs every other minute but just like this one here). I’ve never given any thought to stereo filters at all until now actually, it’d be cool to use it to bring slow, subtle animation to drones and noises!


Is it the stereo aspect of this filter that has folks so pumped up? Wouldn’t you get the similiar effect just patching a stereo signal into two filters? I’m listening to these demos and just thinking, that sounds cool I’m going to try patching this up with what I already have in the rack.


one of the inspiring things about it, I think, is the ease with which the design allows you to control the unit as a stereo pair while describing what should be different about the stereo images. This is definitely something you can patch up with two filters with careful management of CV, of course, so happy patching :wink:


That’s certainly one aspect (and seems to be a major factor in the design). For me, it’s also a versatile filter with a character that I like a lot, based on what I’ve heard. And to me its design invites more playfulness than most other filters that aren’t Three Sisters :grin:


Yeah, for me it’s also the VCA-before-VCF approach which is really interesting tonally.


Was wondering something similar. Hmmm, and I have a Korgasmatron II in my rack…