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françois
Joined: Dec 23, 2006 Posts: 139 Location: Paris (France)
Audio files: 1
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Posted: Fri Dec 29, 2006 5:15 am Post subject:
Percussive envelope generator |
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Hello all,
Here is one of my recently designed modules.
I just got tired of those ADSR envelopes, mostly because you can't know exactly what the "attack peak level" is (90% ? 67% ? other ? voltage controlled ?). It turns out that there is a nice smooth function which, when initiated by a trigger (not gate !) pulse, will rise to its full amplitude, and then fall back to zero.
The function is y(t) = t.exp(-t/T) and is plotted below. The differential equation is "easily derived" (did I mention I was much better at math than music ?) as d²y/dt² + 2dy/dt + y = 0 (trust me) and the resulting analog circuit is exactly similar to a state variable filter, except for the resonance factor of 2.
When mixing this with an ASR envelope and playing with the trigger/gate delays you can get some funny envelopes...
- françois
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Sound
Joined: Jun 06, 2006 Posts: 842
Audio files: 1
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Posted: Wed Jan 03, 2007 12:18 pm Post subject:
Re: Percussive envelope generator |
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françois wrote: |
Here is one of my recently designed modules.
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Where is it?
Do you have any photo?
Thanks a lot. |
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françois
Joined: Dec 23, 2006 Posts: 139 Location: Paris (France)
Audio files: 1
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Posted: Fri Jan 05, 2007 4:46 am Post subject:
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Hello Sound,
Maybe I wasn't clear enough: it is a Spice simulation!
But the circuit is so simple I am confident it will work well on breadboard. Except, probably, for some annoyance due to the OTA's offsets with DC signals. I experimented that already in simulation...
I lack a few $$$ (€€€ in fact) and, more important, I lack room to get a decent lab. I expect to have one shortly but this depends on a friend's good will...
-- françois |
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françois
Joined: Dec 23, 2006 Posts: 139 Location: Paris (France)
Audio files: 1
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Posted: Fri Jan 05, 2007 4:39 pm Post subject:
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Thinking of it, I did in fact test (simulate) this module. LTSpice can generate .wav files as well as taking them as inputs.
It sounds really dull on a linear VCA. Much better on an exponential one.
BTW, my simulated modules already include several types of VCOs, of VCFs, of EGs... A real simulated modular, but simulated at the transistor level... No surprise I can't get real-time !!!
-- françois |
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