HOW TO changing pot value

[bent]

Hi,

I have a question, is it possible to change the value of a pot inside a circuit.
Supposed we take the BSIAB2 (or the blue magic) , there is a 500kB pot for the drive, but i would like it to be 100KB, is there some parts that need to be change around the pot to be able to take down the pot value...

In a simple term, is there a way to take any pot in any schematic and take the value down.....

P.S. i try to search the site, but maybe i didn't use the right term for searching...got nothing...

Thank'S

bent

[Taylor]

Here's a good place to start:

http://www.geofex.com/Article_Folders/potsecrets/potscret.htm

[bent]

Thank's Taylor, 
but i dont want to open the pot and play in it...i want to use another value instead of the one in the schematic, caus e if i used a 100k instead of of a 500k it will affect the sound, but i think there's a way to change some parts around the new value pot so it will not affect the sound....

bent

[MikeH]

If you read it, that article will explain everything your asking.

In short, you cannot make a larger value out of a smaller value (ie- 100k to 500k) without sacraficing a portion of the pot rotation.  You can go the other way (ie- 500k to 100k) using a parallel resistor.

[bent]

hummmm.....
i think i dont explain in good term ( sorry english is my second language), or i dont understand the article ....

i dont want to modified the pot itself, i want to be able to used another value in a schematic...so if the pot is 1M in a schematic, i change some parts (caps+resistor) around the circuit to make it work with (exemple) 100k without affecting the sound that the effect is doing,  cause if a took the original circuit and in place of a 1M  pot i put a 100k pot , the sound of the effect will be affected...

They did that with the Dr Boogey, they lower the tonestack, so instead of volume 1M, presence 100k, treble 250k, mid 22k (ect..), they now have volume 100k, presence 10k, treble 25k, mid 2k5 (ect..)... that's what i want to know, how to reduced the needed value of a pot.... they seem's to reduced by 10 the value of resistor and multiply by 10 the value of caps.... does this can be apply to any circuit ( like the drive pot for the BSIAB2 or Blue magic)...

thank's

Bent
ps; exemple in the BSIAB2, http://www.generalguitargadgets.com/pdf/ggg_bsiab2_sc.pdf, i would like to change the drive pot (R19) from 500K to 50K, do i have to change C6 to 1500PF, R6 to 47K, and C5 to 4700PF, ... if i test side by side a pedal with those new value VS the original schematic, will they sound and act the same...?

[Ice-9]

You could just stick in the 10k pot and test it to see what you think, tthis will change the range of gain though. You could try the 100k pot then add a resistor in series of say 390k (this brings you back to near 500k) and listen to it to see if you prefer it this way. Again that will affect the gain range but in the opposite extreme to just the 100k pot.

What you mention in your example of the Dr Boogie is tone control scaleing. ( this is done to change the pot values for impedeance reasons i think, but buy changing the caps + resistors it keeps the tone correct.)

[jonfoote]

placing a 56k resistor in parallel with C6 should sort that out for you