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PostPosted: Mon Jul 14, 2008 2:56 pm 
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Pre-Setting the Gain, Bass, Mid and Q Trim Pots

Before installing the trim pots you should set them to their stock values first. Once you have done that mark the pots so you will always have a reference point to return to. Once you have done this you can begin tweaking the circuit to your liking. In each photo I have indicated which lead is not used in the circuit. To measure the pot's value connect your meter to the other two leads. Do not take your measurements with your fingers in contact with the leads. This will prevent you from getting a false reading. If you leave your fingers in contact with the leads you will be measuring your body's resistance in parallel with the resistance of the trim pot.

Do NOT try to adjust the Bass trim pot for too much bass. Setting this trimmer too low in value can result in the circuit making odd noises. Same goes for the Gain pot. When you convert a stock Cry Baby to True Bypass there will be a slight volume loss. To offset this loss the trimmer needs to be set anywhere from 48K to about 52K. Go any lower than that and your wah pedal may begin to pick up RFI. (Radio Frequency Interference). Some people like to mount their wah pedals to a pedal board without the pedal's metal bottom plate. I would recommend NOT doing this. Having the plate installed can help to shield the circuit from picking up RFI.

I have the Bass trimmer's stock value shown as 390 ohms. For a Dunlop Cry Baby this resistor may be as high as 470 ohms. The Bass resistor in a Vox wah is 510 ohms.

CW = Clockwise
CCW = Counter Clockwise
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PostPosted: Tue Jul 15, 2008 2:19 pm 
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The photos above apply for the 3386F series trim pots specified in my parts sourcing thread. If you would like to use the 63P series trim pots everything will be reversed (except for the pin that is not used).

Example: A 3386F series Q trimmer gets rotated CW to raise the resistance for a more vocal wah sound. A 63P series pot would get rotated CW to lower the resistance for a less vocal wah sound.

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PostPosted: Sat Jan 09, 2021 11:29 pm 
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So let's just say, "hypothetically", a guy installed all the trim pots and completed his build BEFORE seeing this very helpful post. What would the measurements be for each trim pot in a completed build?

Sorry, I'm a buster... I should have checked first. Can you help?

Thanks!
s


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PostPosted: Sun Jan 10, 2021 8:11 am 
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You can’t measure them in the circuit. It would measure the whole circuit. Start them all at 12:00 and tune by ear.


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PostPosted: Sun Jan 10, 2021 11:10 am 
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Thank you!


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