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 Forum index » DIY Hardware and Software » YuSynth
VCO frequency pot size
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soffiuson



Joined: Apr 15, 2016
Posts: 2
Location: Reykjavik

PostPosted: Tue Oct 29, 2019 8:20 am    Post subject: VCO frequency pot size
Subject description: Does the size matter?
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Hi.

I have built two VCO's that are both working fine. I broke one of the frequency pots on the second oscillator while forcefully tightening it to the front panel Embarassed Unfortunately I don't have another 22k pot to replace it. I have a bag full of 100k pots so I was thinking... Are these pots not basically voltage dividers? What would be the effect of replacing them with 100k pots? I have already replaced them and the oscillator works although I have not calibrated the cv tracking. Is there a reason not to do this?

Regards

Kolbeinn
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JovianPyx



Joined: Nov 20, 2007
Posts: 1988
Location: West Red Spot, Jupiter
Audio files: 224

PostPosted: Tue Oct 29, 2019 8:59 am    Post subject: Reply with quote  Mark this post and the followings unread

welcome I see you're new here - Welcome! welcome

Without a schematic it's hard to say. Not all variable resistors are used as voltage dividers. And some that are used that way are also used as a load resistor for a transistor amplifier. Still others are used as variable resistors. So while in some circuits the value matters greatly (load resistor) and others it doesn't matter much. In some circuits, a higher value may result in increased noise.

We can help much more if you post a schematic of your VCO.

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soffiuson



Joined: Apr 15, 2016
Posts: 2
Location: Reykjavik

PostPosted: Tue Oct 29, 2019 9:15 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi.

Thank you! Very Happy It is the yusynth VCO:

http://www.yusynth.net/Modular/EN/VCO/index.html

The pots I'm referring to are the coarse and fine tune potentiometers.

Regards,

Kolbeinn


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JovianPyx



Joined: Nov 20, 2007
Posts: 1988
Location: West Red Spot, Jupiter
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PostPosted: Tue Oct 29, 2019 9:57 am    Post subject: Reply with quote  Mark this post and the followings unread

The website calls the pots P1 through P6, but they aren't shown on the schematic.

EDIT: I see the wiring diagram now and yes, it's a voltage divider.

I'd test-replace it with the 100K pot and see if the VCO performs as it should. If it works, I'd leave it.

Worst case: might be a bit of noise going into the frequency control circuit.

Best case: it could just work as spec'd.

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gabbagabi



Joined: Nov 29, 2008
Posts: 651
Location: Berlin by n8
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PostPosted: Tue Oct 29, 2019 10:17 am    Post subject: Reply with quote  Mark this post and the followings unread

i would say for the fine tune pot it does not matter much,
cos it is connected to a 3,3M resistor

the 100k will behave bit different from the 22k,
but at least there is no risk in using 100k instead
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