Step 1: Getting the parts
I downloaded the PDF file, there are two options. The first is that you etch your own PCB or you buy a pre-printed board from them. Personally, I prefer saving a bit of money and DIYing it. If you do not have supplies or experience I suggest you find instructions about etching circuit boards first.
The method that I chose is using found here on Instructables.com. It is at this link:
I chose this because it is "reusable" (yeah, i know, I'm cheap). i won't write out the process of etching since it can be found at the link. I will however post pictures of how mine went.
I ordered all the parts from Small Bear Electronics. They are quite reasonably priced without the large shipping costs incurred from mouser. Definitely recommend.
Recently, i read an article about the parts which make up the tube screamer. There is much discussion whether certain parts are better then others. Some claim and swear that by using all NOS(New Old Stock) which means manufactured back when and never used. This is because they it will replicate the exact sound they had back then. I feel that it's great but considering that resistors are still resistors. Caps are still caps and ICs are still built the same.
Consider this, if a precision resistor does the same job as a carbon resistor, just better then why not? After all, one only benefits from less noise. (which is good...right?)
As for the ICs, i hear that people are willing to pay up $45 for a NOS JRC4558D. But consider this, if it was made on the same production line, using the same materials, with no change to the original. What difference does it make?
Then again that is IF those conditions are the same.
Caps(capacitors)...umm...go for the better ones?
which ones are better? here is a list(again with much discussion of order)
1/2.Polypropylene(Film and foil before Metallized)
For the actual audio chain stay away from ceramic and Electrolytics. These caps are still good, just not in audio.
Recently I recieved this comment from Spinergy(located on the bottom of the page) and I realized that it coved what I missed. Thanks
When it comes to caps in the signal path, if the original used electrolytics that's what I'd stick with here if you really so want to dupe the original sound. In an application like this better resistors will make no real difference. The new cleaner IC's will make a small but probably unnoticeable difference. Poly caps in place of electros is where the biggest change will occur. Electrolytic caps are the last thing you'd want in the signal path of your Hifi amp or speaker crossovers, but for something like this their inherently dirty distorted nature is a key part of the original circuit's voice. This is after all part of an instrument making music, not playback gear trying to faithfully reproduce a recording.
While using NOS parts is usually fine if they're cheap and readily available, I'd never go NOS on electrolytic caps. Unlike resistors, IC's, or film caps which are truly "solid state" and will store practically forever without degradation, electro caps are subject to chemical breakdown of the electrolytic paste which makes them tick. Their tolerance isn't great to start, and after 20-30 years their values can be all over the place. Not to mention they can just outright die from old age.
If you want a smoother sound vs. duplicating the original tone then poly caps are certainly the right choice. Electrolytic caps introduce distortion because their internal resistance vs. frequency is nonlinear making them act like a randomly adjusted graphic equalizer. The higher the frequency, the greater the distortion. Poly caps, on the other hand, are very linear and introduce essentially zero distortion.
Which to use in an effects pedal? No right or wrong, better or worse, it's all up to personal choice. They are a tuning element just like choosing your strings, pickups, etc.