madbeanpedals::forum

General => Open Discussion => Topic started by: bigdaddymrx on January 10, 2015, 11:06:53 PM

Title: Can you use a 20K-A pot instead of 25K-A in chunk-chunk build?
Post by: bigdaddymrx on January 10, 2015, 11:06:53 PM
Can you use a 20K-A pot instead of 25K-A in chunk-chunk build? Can't seem to find a 25K-A 16mm solder lug pot.
Title: Re: Can you use a 20K-A pot instead of 25K-A in chunk-chunk build?
Post by: alanp on January 10, 2015, 11:16:12 PM
You could possibly use a 50k pot with a 50k resistor across lugs 1 and 3.
Title: Re: Can you use a 20K-A pot instead of 25K-A in chunk-chunk build?
Post by: midwayfair on January 11, 2015, 12:27:24 AM
Quote from: alanp on January 10, 2015, 11:16:12 PM
You could possibly use a 50k pot with a 50k resistor across lugs 1 and 3.

Not really a perfect solution in this case -- the series resistance will increase at both ends of the travel, because the resistance between the outside lugs to the WIPER will be wrong. A 51K between lugs 2 and 3 and another between lugs 1 and 2, however, would get it to 25K with a slightly weird taper.
Title: Re: Can you use a 20K-A pot instead of 25K-A in chunk-chunk build?
Post by: mgwhit on January 11, 2015, 06:34:01 AM
Quote from: bigdaddymrx on January 10, 2015, 11:06:53 PM
Can't seem to find a 25K-A 16mm solder lug pot.

Mammoth (http://www.mammothelectronics.com/Alpha-Potentiometer-p/200-100-a.htm) has them.  As does PedalPartsPlus (http://www.pedalpartsplus.com/mm5/merchant.mvc?Screen=PROD&Store_Code=PPP&Product_Code=7526&Category_Code=Pot16).  And SmallBear (http://smallbear-electronics.mybigcommerce.com/alpha-single-gang-16mm-solder-terms-linear-audio-taper/).

[Edit: It occurs to me a day after writing this that you probably meant you couldn't find an A25K pot in your personal stash.  If that's the case, I apologize for sounding snarky.]
Title: Re: Can you use a 20K-A pot instead of 25K-A in chunk-chunk build?
Post by: mremic01 on January 11, 2015, 06:46:17 AM
Per Keen's Laws: http://www.geofex.com/effxfaq/keenslaws.htm

1. Use what you can get.
2. Get it running now, and put the perfect parts in later.

You can also put that 25k in there later. If you have multiple 20k's on hand, you might find one that measures in well above 20k.