25 ohm pot replacement

[martyfriedman86]

Hi!
I'm trying to build the little gem amp but i can't get any 25 ohm pot anywhere in town (on one place they could order it for me but it would cost me 40 dollars :S )
Does anybody know If I could use any other pot or something similar?

Thanks a lot!

[joecool85]

It's actually a rheostat, not a pot.  And you could use no rheostat at the end, and just have a pot in front of it for volume control.

[martyfriedman86]

great
but I don't understand where shoud I put the pot
could you please explain me in the schematic or something?
thanks a lot

[joecool85]

Something similar to the ruby.  Basically the tail end would be just like the ruby, and the front end would be whatever you want.  I would just put a pot inline on the signal in of the amp before the cap.  Keep in mind you could just have no pot anywhere and just control the volume via your guitar knob.  I have built two little gems, one has a gain control knob and volume knob, the other is built into a pocket radio chassis so I can clip it onto my pants.  It has a jack to plug the guitar into, and a switch and thats it.  The switch connects pins 1 and 8 directly for full gain.  I almost always play at full volume since its not that loud anyway.  Sometimes if its at night I roll back the volume on my guitar.

[teemuk]

A "rheostat" is a potentiometer that has one end of the resistance element and the wiper connected together, one can therefore built a rheostat from a standard three-legged potentiometer. Needless to say, a standard potentiometer/trimmer potentiometer is therefore much more versatile than a "rheostat" type potentiometer. If you can find a 25 ohm potentiometer you can easily "convert" it to a "rheostat" just by connecting it the way it is shown in the schematic. There is one huge problem though: At the position where the potentiometer is used in the circuit it should be logarithmic type. These, on the other hand, are not usually manufactured with lesser resistance values than 10 kilo-ohms. I'd say that the circuit suggested by Joecool85 is a much better idea to build.