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Phloxs
Joined: Jan 24, 2014 Posts: 17 Location: Russia
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Posted: Fri May 06, 2016 2:57 am Post subject:
Few questions about cd40106 based oscilator. |
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Hello.
Few days ago I lost my backpack with synths. After few hours of hysteria I decided to make my first diy modular. I'm a totally novice in synth building so I choose quite simple osc scheme based on cd40106 Shmidt trigger. On protoboard it sound not perfect, but not awful same time.
So I have few questions:
1 - All schemes I found use variable resistor to control pitch. Is it possible to use add additional control with buttons + resistors (for ex. variable resistor for lowest note tuning and buttons for chromatic scale)?
2 - how can I realize pulse width modulation for osc?
I use this scheme but without triggering between low and hight freqs.
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Grumble
Joined: Nov 23, 2015 Posts: 1294 Location: Netherlands
Audio files: 30
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Posted: Sat May 07, 2016 3:30 am Post subject:
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Replace R2 with a potmeter of 5k, and feed the runner in another cd40106 schmitt trigger inverter.
The output of this inverter will have a variable pulsewidth, set with the potmeter. |
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robTech
Joined: Aug 30, 2016 Posts: 1 Location: Germany
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Posted: Tue Aug 30, 2016 3:46 am Post subject:
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Hi,
making your own modular is a very good idea...
surely you could add a number of potentiometers and switch always one of these by a number of buttons; but the typical modular way is frequency control by an external voltage (this voltage can come from either a keyboard, a MIDI-CV-Interface, a Sequencer... so you are much more flexible).
For pulse width modulation add a so-called Schmitt-Trigger (created with an OpAmp IC) at the triangle output; this circuit switches to high output at a selectable threshold level. If the threshold level is e.g. little below the triangle peak, you get a narrow pulse out, lowering the threshold makes pulse wider.
Give me some time, I will add a circuit that will answer your question. I developed a low cost modular synth shortly - I'm also using 40106 for the oscillators |
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