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synthmonger
Joined: Nov 16, 2006 Posts: 578 Location: flada
Audio files: 3
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Posted: Sun Jun 07, 2009 9:16 pm Post subject:
3 Channel gatewidth Modulator Subject description: name changed added schematic |
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I redesigned my Lunetta-esque pulsewidth modulator circuit into something a bit beefier, easier to control and a heck of a lot more fun to play with!
I've been troubled for a while now getting good pulsewidth modulation out of the 40106 chip and I've found the solution today by using FETS over NPN/PNPs.
The controls for the PWM are as follows:
CV input and manual frequency control for each channel
Input for each channel
Output and non inverted output for each channel with LED indicator
It's finished now and I'm going to be working on the PCB/schem as well as a new scope/audio demo this week.
To make this thread worthy I've included an audio clip. The input signal is running through a frequency divider whose /2 /4 /8 outputs are running into each channel. I'm using one triangle or noise output from my triple Modulation source (think CGS Pyscho LFO but CVable and insane) to control the PW. The PWM outputs are mixed together at different levels through an external mixer. The levels sound like they're being faded in and out but thats just due to the width of the signal being hardly audible.
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_________________ Youtube!
modular demos!
Whacky tunes! |
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synthmonger
Joined: Nov 16, 2006 Posts: 578 Location: flada
Audio files: 3
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Posted: Tue Jun 09, 2009 4:34 pm Post subject:
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Added a schematic!
It accepts just about any input signal. Works splendidly for gate signals and low frequencies, not so good with mid-high frequencies. _________________ Youtube!
modular demos!
Whacky tunes! |
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fonik
Joined: Jun 07, 2006 Posts: 3950 Location: Germany
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Posted: Sun Jun 14, 2009 3:35 pm Post subject:
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so you are using a FET to creat a variable resistance!? great.
thanks for sharing. i almost missed it _________________
cheers,
matthias
____________
Big Boss at fonitronik
Tech Buddy at Random*Source |
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synthmonger
Joined: Nov 16, 2006 Posts: 578 Location: flada
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Posted: Sun Jun 14, 2009 3:39 pm Post subject:
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fonik wrote: | so you are using a FET to creat a variable resistance!? great.
thanks for sharing. i almost missed it |
Yep! It works better than any PNP/NPN combo. I tried it with a few other circuits. One of them was the Resonator. I replaced the vactrols with two Fets and it worked kind of ok. I think my use of 4007's instead of the vactrols worked better. _________________ Youtube!
modular demos!
Whacky tunes! |
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funkyfarm
Joined: Jan 21, 2007 Posts: 583 Location: France
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Posted: Sun Jun 14, 2009 6:24 pm Post subject:
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Great !!
this is kind of digital "voltage control gate length"
"3 channels" ? were is the pcb ? |
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synthmonger
Joined: Nov 16, 2006 Posts: 578 Location: flada
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slo
Joined: Feb 18, 2007 Posts: 204 Location: Victoria, BC
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Posted: Wed Jun 17, 2009 7:09 am Post subject:
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Looks like this is what I need, I think.
Questions
Can it operate as a simple gate strecher if I left off the CV circuitry?
Should there be a dot at the junction of R6 - R5 joining them to the FET input?
I'm assuming R8 is the width control
George |
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synthmonger
Joined: Nov 16, 2006 Posts: 578 Location: flada
Audio files: 3
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