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DSM01 Curtis Filter Thoughts

chysn

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DSM01 Curtis Filter Thoughts
« on: June 08, 2016, 06:59:39 AM »
The DSM01 is very much the sound I wanted it to be, and it does things that a Moog filter can't do. On other forums, people have compared it to the Pro One filter, but I can't speak to that. What I can say is that it sounds just like a Mopho, and it's great to have that sound back under modular control.

The build quality is good; the knobs aren't as rock-solid as Doepfer modules, but aren't as wiggly as Make Noise modules. The pot shafts are metal, and it's made in San Francisco, like other DSI products. The controls are nicely spaced, and clearly marked. "Clearly marked" is nothing to take for granted, as other eurorack makers try to make their panels as bewildering as possible (I'm looking at you, Make Noise).

Until you start patching stuff up, you don't know how convenient it is to have a VCA built into the filter. That's a very considerate touch, and leaves any other VCAs you have available for other duties. But if you wanted to build a minimal eurorack system, you could get away with the DSM01 as your only VCA, as long as you don't mind your signal always going through the Curtis filter.

The filter is switchable between 24dB and 12dB modes. The 12dB mode sounds good, and will be useful, but note that in 12dB mode, the resonance control does almost nothing. I mean, it does something, but it's confusing. It's not what I'd think of as "resonance." It seems to behave almost like a tiny high-pass filter.

The bottom line is: I'm happy I got it.

A picture of my synth is below. That big, gaping maw there is earmarked for a Triatt mixer, and the DSM03, which will make it complete, at least until I replace the oscillator.
DSI: DSM03; previously: Mopho Keyboard, Desktop Mopho, Evolver, DSM01
Hardware: Eurorack, Moog Little Phatty w/ CV Outs, Arturia MicroBrute, KMI QuNexus
Software: macOS, Ableton, MuseScore
Modular Grid: https://www.modulargrid.net/e/racks/view/354385
GitHub: https://github.com/chysn

Re: DSM01 Curtis Filter Thoughts
« Reply #1 on: June 09, 2016, 06:56:57 AM »
Nice to hear your report.
Have you tried feeding the signal from the filter back to the input, like on the Mopho/Tempest?
I really like the sound of 2-pole filter with resonance on full with some feedback added on the Mopho and wonder if you can get the same effect with the DSM01.

chysn

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Re: DSM01 Curtis Filter Thoughts
« Reply #2 on: June 09, 2016, 08:33:21 AM »
Nice to hear your report.
Have you tried feeding the signal from the filter back to the input, like on the Mopho/Tempest?
I really like the sound of 2-pole filter with resonance on full with some feedback added on the Mopho and wonder if you can get the same effect with the DSM01.

So, I was going to put together a video and put it on YouTube, but I must be doing something wrong, because the sound is unaffected by what I'm doing.

(1) Little Phatty CV pitch Out to 1v/Oct In of the oscillator.
(2) I'm borrowing one of the LP's envelopes, going into the DSM01's VCA In.
(3) The saw Out of the oscillator goes to the first mixer In.
(4) The DSM01's VCA Out (which is post-filter) goes to two destinations via multiple: the second mixer channel, and the main audio Out to the amp.
(5) The mixer Out (which mixes saw Out and post-filter VCA Out) goes into the DSM01's audio In.

This looks like it should be a feedback loop to me, but there's no audio difference between doing this, and sending the DSM01 straight to the amp. So I've either got issues with level, or signal path. Chalk it up to inexperience. I'll soon have another mixer, with which I can control one of my other VCAs, and I'll try this again by increasing the gain of the mixer Out.
DSI: DSM03; previously: Mopho Keyboard, Desktop Mopho, Evolver, DSM01
Hardware: Eurorack, Moog Little Phatty w/ CV Outs, Arturia MicroBrute, KMI QuNexus
Software: macOS, Ableton, MuseScore
Modular Grid: https://www.modulargrid.net/e/racks/view/354385
GitHub: https://github.com/chysn

Steven Morris

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Re: DSM01 Curtis Filter Thoughts
« Reply #3 on: June 18, 2016, 09:32:42 AM »
Your notes and thoughts are very much appreciated! Thank you :)

RE: 12db Filter Resonance
I actually use the 12db filter's resonance control as a way to remove low frequency content from my MoPho patches! It's nice to know that the module version of the filter responds in the same way.

Also, welcome to the world of modular!!

chysn

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Re: DSM01 Curtis Filter Thoughts
« Reply #4 on: June 18, 2016, 09:52:26 AM »
Steven, thanks!

Do you have any ideas about how to feedback the filter (see above)?
DSI: DSM03; previously: Mopho Keyboard, Desktop Mopho, Evolver, DSM01
Hardware: Eurorack, Moog Little Phatty w/ CV Outs, Arturia MicroBrute, KMI QuNexus
Software: macOS, Ableton, MuseScore
Modular Grid: https://www.modulargrid.net/e/racks/view/354385
GitHub: https://github.com/chysn

chysn

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Re: DSM01 Curtis Filter Thoughts
« Reply #5 on: June 21, 2016, 04:53:16 PM »
Have you tried feeding the signal from the filter back to the input, like on the Mopho/Tempest?

Benzebub, I'm still working on answering this question. I'm almost there. I now have a Triatt mixer, so I can feed the VCF Out of the DSM01 back into the signal path. This does work. The effect is really subtle, but now I know that it's just a matter of amplitude; so when I get my new skiff tomorrow, I'll be able to put the return signal through its own VCA, hopefully with a more pronounced tone.

Right now, I'm really appreciating the 12-pole mode of the DSM01. It sounds huge.
DSI: DSM03; previously: Mopho Keyboard, Desktop Mopho, Evolver, DSM01
Hardware: Eurorack, Moog Little Phatty w/ CV Outs, Arturia MicroBrute, KMI QuNexus
Software: macOS, Ableton, MuseScore
Modular Grid: https://www.modulargrid.net/e/racks/view/354385
GitHub: https://github.com/chysn

Re: DSM01 Curtis Filter Thoughts
« Reply #6 on: June 23, 2016, 02:56:55 AM »
Have you tried feeding the signal from the filter back to the input, like on the Mopho/Tempest?

Benzebub, I'm still working on answering this question. I'm almost there. I now have a Triatt mixer, so I can feed the VCF Out of the DSM01 back into the signal path. This does work. The effect is really subtle, but now I know that it's just a matter of amplitude; so when I get my new skiff tomorrow, I'll be able to put the return signal through its own VCA, hopefully with a more pronounced tone.

Right now, I'm really appreciating the 12-pole mode of the DSM01. It sounds huge.

Sorry for late reply and thank you very much for your response. Good to know that it seems doable, albeit with some extra modules.
I really like the 2-pole sound as well. When the day comes I start building a modular I think I will start with the DSM01 filter in the system.