I've gotta backfill a little before I start on this...
There are some great caches of circuit diagrams on the Web. Here's one:
http://www.montagar.com/~patj/gindex.htmIf you read the list & mutter the filenames under your breath, you'll recognize many of 'em quickly enough.
When I first thought of making a few boxes myself, I realized that I didn't want to mess with fiddly components -- if a circuit specified a certain transistor, it was almost impossible back then (without going to a bench tech) to find a full list of equivalences or substitutions, & if it called for a Motorola part, I was pretty much out in the cold. And I didn't feel I was up to finding odd parts like "operational transconductance amplifier" chips central to the Small Stone phaser:
http://www.montagar.com/~patj/smlstone.gifI don't know about "three families," but Jankowiak does agree that the MXR Distortion+ is one of many variants on the same basic circuit... one of them being the DOD Overdrive 250 that I started from:
http://www.montagar.com/~patj/dodoverd.gifLet's use this as an example for the foregoing discussion.
Reasons to build it? It's simple. It uses VERY common components. It's a classic sound. It's so "old school" that few makers are putting it out.
In descending cost, you need:
a box
a board (PC or turret)
two pots
footswitch
two jacks
741 op amp
two electrolytics
three caps (mylar, disk, whatever's handy)
seven resistors
two diodes
battery clip
(If you want, you could put the chip into a socket, or even a ZIF.)
Running down that list, paying one-off prices, you're probably talking something like $25. If your bench is well-stocked &/or you buy components in lots of +/- 100, & go with perfboard, it'd be more like $10.
...which beats heck outta $60 from a kit-vendor. Even if we go with the $25 figure, & factor in two hours' work at $10/hour, that's a geat margin if you sell it at boutique prices of $100+.
Compare the DOD circuit to the MXR:
http://www.montagar.com/~patj/mxrdistp.gifThis also will give you some mod potentials, thus ensuring that YOUR box is unique in the market. And among Tube Screamer maniacs, there's vicious fights over WHICH 741 equivalent is best, so there's even more potential (hence my suggestion of the ZIF socket, maybe even top-mounted).
If you're willing to mess around with transistors, the world is your virtual oyster. Here's a two-x circuit apparently made by Jim Dunlop to clone the Hendrix sound:
http://www.montagar.com/~patj/jhfface.gifThe Zener is the only really offbeat part.
Double the parts-count & you've got a classic Maestro:
http://www.montagar.com/~patj/maefuzz.gifBump it up another 50%, & you've got a Univox Super-Fuzz:
http://www.montagar.com/~patj/uvspfuzz.gifBack in the early 1970s, I shared one of these badboys with my cousin, & I can testify that it kicks ass. The original Univox commonly sells $400+; the Black Cat clone goes for about $200. Tweak the cap values, put in another knob or two to modify response, & there -- you've got a SERIOUS boutique pedal, for not much more than the cost of six transistors & a box to hide 'em in. Find some art-school kid to paint the boxes for you, & you're set.