I had some problems zeroing in on some resistance and capacitance values building a tube-distortion stompbox. Inspired by Matt-the-Modulator's work ( http://www.flickr.com/photos/matt_the_modulator/3874753521/in/pool-make/ ), I created a simple interface to swiftly switch values of one or both.
Please bear the lack of step-by-step pictures. I didn't plan an instructable.
Step 1: Choose Resistance and Capacitance Values You Want.
I chose to use a dipole, 6-way switch for each component type. Thus, 12 resistors and 12 capacitors are available for use.
Being geared towards music, I chose resistors from packs of carbon composite resistors purchased on ebay. These were 1/2W capable.
For capacitors, one pole was filled with 6 non-polarized values. The other pole had 2 tantalum and 4 standard polarized values.
Since some schematics call for sound-altering diodes, I added a standard (1N4001-1N4007) type,a small switching type, and an LED to one side.
Step 2: Get Parts.
I pulled the 3 component types and a Radio Shack PCB from my stockpile-o-stuff. Next, I purchased the 2 switches and a 4"x2"x2" black plastic box from Radio Shack, as well as a small euro-style barrier junction strip.
Step 3: Plan the Layout.
Using pre-formatted PCBs takes some planning. I used an almost-breadboard style that worked beautifully.
Step 4: Put It Together.
Put it together. I had some large capacitors, so creative placement was needed. Just trying to save a buck by using stocks on hand.
Please ignore the polarization scribbles. Plans change when components hit the board.
They aren't visible, but I scraped the copper from the center of the 2 input busses to create 4 instead.
Step 5: Wire It Up.
Know your switches' positions. Use enough length for mounting, but too much can create a headache (and stray capacitance!).
Step 6: Drill Holes.
Inputs, outputs, and 2 switches. Don't forget screwholes for barrier strips! That made 15 holes for me.
Step 7: Mounting and Testing.
Mount your hardware. Insert inputs and outputs. Test your work with a multimeter. Got it in one! Made me feel good!
It turned out I didn't need to mount the board. It just worked out.
Don't forget to label!
With this setup, I can not just switch between one or another value, I can serial or parallel the in/outs for other resistance and RC values. If you don't mix polarizations in your design, that can be done with capacitance. I imagine strange results if I mix that on mine, though.
When you get the sound (or other result) you desire, plug them into your finished project.