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 Forum index » DIY Hardware and Software » ChucK programming language
ChucK + MOTU Ultralite = CV out!
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Antimon



Joined: Jan 18, 2005
Posts: 3739
Location: Sweden
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PostPosted: Sun Apr 19, 2009 5:51 am    Post subject:  ChucK + MOTU Ultralite = CV out! Reply with quote  Mark this post and the followings unread

I've been sweating over my SoundLab from MFOS (some woes and pics here), and while I've been doing that I've been thinking that it would be cool to try out that MOTU Volta thing I've been hearing about, and plug my soundcard into the CV inputs in the soundlab. Having analogue/cv stuff around is pretty new to me, and I've grown increasingly excited about it all, getting modular GAS from Jyotis postings and comments etc.

Anyway, Volta seems to be floating in limbo a bit - there is no mention about it on Motu's homepage, and googling for it just finds old pages, plus Stretta (I think it was) who did the cool demo video and is pretty active on the monome forum hasn't mentioned it recently (as far as I know, I sometimes miss posts on the monome forum). So that's a bummer. But then I thought, if they can do a plugin that does this without any hardware mod needed, maybe I can do it just as easily from ChucK! So I tried it - and I can! Very Happy I hooked the first soundcard output (not of of the main outputs, also I need to run ChucK with extra options to make it use the other outputs) up to my new scope (a very nice purchase), and saw a signal moving from a steady -something to a steady +something (I haven't learned to read the volts on the scope yet).

This is the ChucK program I ran:

Code:
SqrOsc sqrOsc => dac.chan(0);

1 => sqrOsc.freq;

while (true) {
        1::week => now;
}


Attached is a sample of my soundlab being controlled by this signal, first through the gate input then through the oscillator 1 input. Correct me if I'm wrong, but there should be nothing to stop us from doing whatever kind of wild sequencing or controlling or whatever from this kind of soundcard's output into analogue gear with CV inputs. Is this cool or what? Very Happy I'm glancing at my monome with a new kind of lust... Twisted Evil

The question is then, what kind of soundcards can support this? I'm guessing my Ultralite's outputs are not DC coupled (is this the right term), otherwise it wouldn't have worked, right? Volta is supposed to work for all MOTU's stuff.

/Stefan


CVd MFOS.mp3
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Antimon



Joined: Jan 18, 2005
Posts: 3739
Location: Sweden
Audio files: 277
G2 patch files: 96

PostPosted: Mon Apr 20, 2009 9:16 am    Post subject: Reply with quote  Mark this post and the followings unread

After the first enthusiasm ebbed out I realized that this might be old hat, and if you're into ChucK maybe you're not into hardware, but well...

Anyway, I checked this code (a bit more intuitive way of specifying a dc level on the output), and found out that you can use the interval -2.0 to 2.0 to set the output voltage to the interval -4V to +4V. So when I checked this code, the -2.25 wasn't different from -2 on the scope (-4V) and 2.25 wasn't different from 2 (+4V). Reading on another forum (99.se) about hacking soundcards the general feeling is that this isn't enough for serious use in modulars (they're messing around with amplifiers and stuff). Should be usable for gates though.

Code:
SqrOsc cv1 => dac.chan(0);
SqrOsc cv2 => dac.chan(1);

0 => cv1.freq;
0 => cv2.freq;

while (true) {
        0.5::second => now;
        -2.25 => cv1.gain;
        0.5::second => now;
        -2 => cv1.gain;
        0.5::second => now;
        -1.25 => cv1.gain;
        0.5::second => now;
        -1 => cv1.gain;
        0.5::second => now;
        0 => cv1.gain;
        0.5::second => now;
        0.25 => cv1.gain;
        0.5::second => now;
        1 => cv1.gain;
        0.5::second => now;
        1.25 => cv1.gain;
        0.5::second => now;
        2 => cv1.gain;
        0.5::second => now;
        2.25 => cv1.gain;
}


/Stefan

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Kassen
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Joined: Jul 06, 2004
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PostPosted: Mon Apr 20, 2009 3:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

Antimon wrote:
After the first enthusiasm ebbed out I realized that this might be old hat, and if you're into ChucK maybe you're not into hardware, but well...


I think it's interesting and relevant. I have a E-MU instead and aside from some pedal inputs here&there no CV controlled synths so I can't replicate your findings but I think this is quite interesting.

I did one brief livecoding set using ChucK and a analogue synth (a Blippo Box by Rob Hordijk) that I sampled live and treated and I think there are many, many more interesting possibilities in combining the two. For one thing analogue sequencers tend to be fairly simple, even when the sounds they control are rich, that's a gap that could nicely be filled by a system like this. I hope you'll keep us posted.

I'm still wondering how this works, BTW, maybe it's high frequency PWM? -4 to +4 V is still 8 octaves in a volt-per octave system, right? That should do the trick, I imagine, that's a larger range than any grand piano I ever heard of, maybe I'm missing something.

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Antimon



Joined: Jan 18, 2005
Posts: 3739
Location: Sweden
Audio files: 277
G2 patch files: 96

PostPosted: Tue Apr 21, 2009 3:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for your input Smile

I pretty new to CV overall, so I read up a bit. I had gotten the impression that there were loads of different standards (especially for modulars) floating around, but maybe I am confusing cv with power supply voltages.

This wikipedia article mentions two standards: http://en.wikipedia.org/wiki/CV/Gate . The control per voltage looks like the most common, so I think you are correct that 8Volts would present an OK range. Possibly not all synths will accept negative voltages? That would mean only 4 octaves, which still is big enough to be usable for stuff. I think I'm going to try sending stuff into my Evolver CV inputs tonight and see what happens.

/Stefan

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