I'm having problems finding pots that i need. What I'm working on is a power supply with variable voltage from 0-20V at 3A max. I'm using a lm317 with a bypass transistor to allow for more current.

The LM317 uses a 5k trim pot to control Vout. I was going to use two 2.5k or a 5k and 1k in series to give me coarse and fine adjustment of my voltage. but I've seen a fair amount of power supplies that two knobs on top of each other, but i can't seem to find them anywhere.

does anyone know where i get get a couple?

 

For the odd values, you may need to get a custom made pot. Concentric shafts will give the fine/coarse controls (although the trimmer will always be superior for absolute adjustment). Here is a link you can explore - http://www.potentiometers.com/

 

Another alternative is to use a 10 turn pot with a turns counting dial. That will give you very fine control and a scale for quick setting.