I HAVE CREATED A NEW INSTRUCTABLE FOR DIY CONTROLLERS:
I have spent endless hours searching for the best and most reasonably priced components from around the world. I ordered many different components to test out and compare, most of them were rubbish and were not used in project. Here is the list of the best stuff I found. The ones with * are my favorites.
(Many of these pushbuttons are available in different sizes and color - check the sites for more options. With pushbuttons, you usually get what you pay for.)
(If these are out of stock, they may also be available at digikey.com or newark.com. If you are a scratch DJ you probably demand a 'frictionless' fader. DJ Deals sells them for cheap, and they are simple enough to use with the DIY controllers.)
(Knurled knobs can only be attached to knurled shafts. Knobs with set screws will require a hex key to couple with the potentiometer. 6.4mm knobs coupled with 6mm shafts fit slightly non-concentric - this can be fixed with some scotch tape. 6.35mm potentiometers do exist although I was unable to find an economical option.)
(Search 'PEC11-' on Newark to get a long list of nice and affordable encoders. I used PEC11-4115F-S0018 and PEC11-4215F-S0024 in my build. I tested many encoders and found the Bourns ones to be best. They have both D, and knurled shaft options available.)
Wires & Connectors
(Sure electronics is by far the cheapest!)
(Every site has plenty of different LED options. Keep in mind this controller framework is not really designed to control more than a few LEDs. Now that is not to say you can't use many LEDs in this project, you just can't control them, ie, turn them on and off when you please.)
All hardware (nuts, bolts, standoffs) can be found at McMaster (USA). McMaster is the best!
Soldering iron, wire cutters/strippers.
There are many other components you may want to include in your interface such as LCDs, touchscreens, trackballs, pressure pads, proximity sensors, etc. SparkFun and Adafruit are the best resources for these kinds of components. Although the controllers I showcased in this Instructable are somewhat conventional, I encourage you to get crazy. DIY gives you the power to do anything you can imagine - just wait till you see the next controller I am going to build!
Read the datasheets carefully before buying components.
Discount/surplus stores like Futurlec & All Electronics have excellent prices, but also carry some components which are totally bogus - be extra careful before buying from these stores.
Note that all these components are panel mount (with exception to the LEDs). There is an important distinction between surface mount and panel mount components. Surface mount components fasten directly to the printed circuit board (PCB) while panel mount components fasten to the top panel and connect to the PCB via wire and solder connections. It is usually not possible to use surface mount components unless you fabricate custom PCBs and have expert soldering skills. Using panel mount components makes this project accessible to anyone.
So how much do these controllers cost? I don't kow how much your controller is gonna cost but mine were cheap, really cheap!
If you are from Europe or Asia this list may not be totally relevant or useful. Please send me links to suppliers in your countries so I can add them to this document.