So I used the schematic with the square wave, the PWM and the PWM CV. (https://www.lookmumnocomputer.com/projects#/cem-3340-diy-simple)
I’ve got a problem with it. The square wave is working, but just when I tweak the PWM pot to a certain point. Else, I don’t have sound for the square wave. I cheaked, but I think i soldered it as it’s on the website.
What could be the problem?
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The PW work only with the square wave, and it’s normal that there is a dead part with
the pot
it works but when the pot is at zero = no sound and fully either ?
I added a trim pot to remove the dead part when the pot is full
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Thanks, for the answear.
Can you share the schematic?
i have no schematic for this, … i make a little draw quickly
maybe 10k trim pot ? try
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The square wave is generated by running the sawtooth through an internal voltage divider and comparing it to the control voltage, which gives you an effective range of just over 0 V to just under 4 V (supply/3). The circuit still works, it’s just that you cannot hear a signal that’s 100% on or 100% off 
(this is common in DIY circuits since the alternative is trimpots everywhere, and you need to be able to tweak your CVs anyway so people usually don’t care that much about what happens at the boundaries…)
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Clever idea. My Behringer Crave has a dead spot like this as well. A trim pot would be a great solution there.
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like said @fredrik
I did the same in a lot of circuits (it really helps), the resonance pot of the MS20 for example to calm down the high frequencies of the auto oscillation, while keeping what I want
vive le trim pot !
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Not sure what dead spot you’re referring to, but if it’s the VCO there are a couple of trimmer screws next to the frequency knob on the Crave that can be used to adjust the linearity and range of the tuning.
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Once you’ve figured out what the value should be, a fixed resistor should do just as well.
It’s not something you should need to ever change.
EDIT: Clarified my thought.
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yes indeed, but what I find interesting with the trim pot is that we can make the adjustment once the module is completed without the need to reweld somethings
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I was thinking of the PWM modulation of the square wave. This can be chosen in such a way that there is no audible signal anymore.
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Indeed, if the prototype is the product, i.e. no breadboarding, then sure, you might as well build the trimpot right in.
PTI: On utilise “weld” pour souder des pièces de métal avec une soudeuse à l’arc ou des torches à l’acétylène etc, et “solder” pour souder des circuits électroniques avec un fer à souder ou de l’air chaud.
C’est drôle, dans le premier jet de ce message j’avais aussi fait un gallicisme en écrivant “effectively” au lieu de “indeed” ci-haut. J’habite aux États-Unis depuis plus de 10 ans et je fais encore des gallicismes, je trouve ça un plutôt bon signe pour ma résistance à l’assimilation. Ça l’air que y’a pas juste les gaulois qui sont irréductibles (je suis québécois).
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I’ve noticed this use of “weld” by some non-native speakers. From context, it’s always clear when one is speaking of “welding” part of an electronic circuit. One thing I’ve noticed is even in English the pronunciation of the word “solder” varies quite a lot. Americans pronounce it as if it were spelt “sawder”, where British speakers tend to pronounce it to rhyme precisely with “older.” I’m not sure how Australians and others in the anglosphere pronounce this word.
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