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DSM-01 VCA Questions

chysn

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DSM-01 VCA Questions
« on: May 21, 2016, 04:09:41 PM »
Two questions about the DSM-01's integrated VCA:

(1) Is it a linear or exponential VCA?

(2) Let's say I try to use it as my eurorack synth's only VCA. What limitations would I encounter?
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: DSM-01 VCA Questions
« Reply #1 on: May 22, 2016, 03:32:21 AM »
Two questions about the DSM-01's integrated VCA:

(1) Is it a linear or exponential VCA?

(2) Let's say I try to use it as my eurorack synth's only VCA. What limitations would I encounter?

Hi Chysn!

Prefacing my comments with the fact that I have no experience with the module in question- so I'm addressing everything in a general sense.

(1) I don't know the answer, but do know that if you're feeding envelopes into it (which is often the case), those envelopes can also be linear or exponential, etc. So while the 'snappiness' of a sound often relies heavily on an exponential VCA, whether the envelope you are using is linear or not will also affect that.

(2) By a technicality, you can also use an LPF as a VCA. LPG's are also often used as such. Not sure about this, but the slope of the filter might also affect how 'exponential' it sounds as a VCA.

I could have sworn Tuesday Night Machines had a YouTube video on that, but I'm having trouble finding it.

Assuming you understand the limitations of having just one VCA (which are immense), there are still limitations to this particular VCA judging by what's available on the front panel relative to what is available on other VCA modules out there. I'm going to avoid trying to explain the difference with some of the more esoteric VCA's like those that Make Noise offers.

If you look at what Pittsburgh Modular, Intellijel, or Doepfer have to offer, you'll notice that they all have two knobs per channel. One controls the amount of CV-- in other words, it allows you to decide how high the volume will go at the peak/trough of an envelope or LFO. This is something that could be solved with an attenuator though.

The next common feature is a knob that sets how much of the signal is passed through even if the CV is at 0. This is good for tremolo type effects, where you don't typically don't want the signal to ever reach '0'. Of course you can also do that with by splitting the signal and sending the non VCA'd signal and the VCA'd signal to separate channels of a mixer. There are other uses in more complex patches as well.

Another, although less common, feature is the ability to choose whether the VCA is linear or exponential. This is one of the many areas where Intellijel's design shines since it uses a continuous knob for this choice.

Don't get me wrong though, I think the inclusion of a simple VCA on the DSM01 is a genius move and makes it very appealing. Sometimes I wish more modules included simple VCA's on them as it 1. saves space and 2. saves using a VCA on a pedestrian (although vital) function.

Hope you don't mind the long answer and I hope that my ramblings will help you out in some way.

chysn

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Re: DSM-01 VCA Questions
« Reply #2 on: May 22, 2016, 05:09:38 AM »
Hope you don't mind the long answer and I hope that my ramblings will help you out in some way.

I very much appreciate your time, and this is extremely helpful.

Quote
Assuming you understand the limitations of having just one VCA (which are immense), there are still limitations to this particular VCA

I don't think I have an appreciation for those limitations. When I used the CP-251, I controlled CV levels using attenuators; so I had planned to use attenuators for that in my eurorack system, and then have one VCA for audio output.

Keep in mind that the synth I'm putting together will be based around the DSM-03, and that I'm not necessarily going to have a dedicated filter. But Curtis/VCA seemed to be a good use of space.

If I'm understanding correctly, it might be a good idea to ditch the attenuators, and have a few VCAs instead. Or are attenuators still worthwhile for some reason?

Thanks again for sharing your knowledge!
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: DSM-01 VCA Questions
« Reply #3 on: June 07, 2016, 05:40:21 PM »
The DSM01 box has a signal path diagram on it that answered pretty much all of my questions about it.

So... why isn't this diagram anywhere else? Like, the DSI website on the DSM01 page? I bought it because I wanted a Curtis Filter, but my decision would have been a lot easier (i.e., I would have bought it right away) if this information were on the website.

The integrated VCA is really a brilliant idea, and frees up my other VCAs for things like velocity control.
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