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 Forum index » Instruments and Equipment » Modular Synthesis
Few questions about cd40106 based oscilator.
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Phloxs



Joined: Jan 24, 2014
Posts: 17
Location: Russia

PostPosted: Fri May 06, 2016 2:57 am    Post subject: Few questions about cd40106 based oscilator. Reply with quote  Mark this post and the followings unread

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: 994
Location: Netherlands
Audio files: 27

PostPosted: Sat May 07, 2016 3:30 am    Post subject: Reply with quote  Mark this post and the followings unread

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

PostPosted: Tue Aug 30, 2016 3:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi,

making your own modular is a very good idea... Smile

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 Wink
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