Re: "Types" of distortion pedals?
IMO, there are a few reasons for this. First of all, getting the right boost/overdrive/distortion/fuzz that works well with your amp and guitar (and other pedals) is a pretty important part of your core sound. Subtle differences can make all the difference for your ear and gear. However, they are also the easiest pedal to make, and by taking standard circuits and doing a few tweaks you can easily make a new drive pedal that's just a little different than everyone else's.
I'll just do a stream of consciousness on my thoughts on different Drive pedals.
Boost:
-Clean: a literal clean boost that can be used to make your guitar louder or push the next stage in your chain harder for breakup. (See: Keeley Katana)
-"Dirty": a boost similar to the clean, but it'll inject a little of its own breakup by transistors or opamps distorting. (see TC Spark Boost)
Overdrive:
Generally speaking overdrives use "soft clipping" diode arrangements. If you look at the guitar waveform on an oscilloscope, the peaks of the wave will "softly" turn over into clipping. Generally used to either add "tube style" breakup to an amp, push the next stage harder or both.
-Tube Screamer style: a soft clipping overdrive with a stereotypical "midrange hump". It rolls of the bass, increases midrange and adds the diode clipping (See Tube Screamer, Boss SD-1)
-"Standard": massive range of options, basically take the idea of a tube screamer but tune the EQ so not as much bass is rolled off and the midrange is less prominent. (See Boss Blues Driver, and most modern overdrive pedals)
-"Transparent": ideally a "flat" EQ overdrive, that is supposed to sound like your guitar and amp, but "more". If you like the overall breakup and tone of your guitar/amp, this should just add additional breakup through boosting the next stage, adding clipping or both. (See Paul C Timmy)
Distortion:
These are usually separated from the overdrive category by their usage of "hard" clipping. The signal has a sharp limit rather than the smoother clipping of the overdrive style.
-Classic style: uses an opamp and diodes to ground to provide the classic hard clipped sound. Can be used as a sole source of breakup or to layer over amp breakup. The EQ options are endless, from flat, to scooped mids to boosted mids. (See RAT, MXR Distortion +, Boss DS-1)
-"Amp Style" using FETs. Most of these bill themselves as "Marshall in a Box", but they are using FETs to amplify and clip the signal, which combined with a classic Marshall tone stack can kind of approximate an amp tone and feel. At least more so than the classic diode clipped circuit. (See BSIAB, Zvex Box of Rock, Wampler Plexi-Drive)
Fuzz:
Probably the first distortion effect, they are usually pretty primitive transistor circuits that go to square wave clipping quickly.
-60's style: super gritty and nasty. Think Spirit in the Sky or Satisfaction (See Mosrite Fuzrite, Maestro FZ-1)
-Fuzz Face style: Next generation, buzzy clipping, but also do a really cool overdrive tone with the guitar volume backed off.
Think Hendrix's tone. (See Dunlop Fuzz a Face, Fulltone 69, 70, etc.)
-ToneBender: next step after Fuzz Face, the one most are familiar with use a third transistor for more distortion, early Jimmy Page was a big user. (See Tonebender, Throbak Stonebender)
-Big Muff: Uses transistors and diodes to clip, plus a scooped EQ. Originally designed to sound like Hendrix's fuzz face into cranked Marshall. The singing Gilmour sustain and grungy fuzz riffs both use the smooth breakup of the muff. (see Electro Harmonix Big Muff)
Like I said, those are just off the top of my head, from least gain to most gain. Some guys are going to split hairs over my definitions, say I missed some major category, or that I way over-simplified it, but regardless, I think a good chunk of pedals fit into these categories.
Most boutique circuits are based on one of those base circuits, then tweaked for different EQ, clipping (harsher/smoother, more/less), and overall response. You are right, there are a million gain pedals out there now, but I think you can go into Guitar Center, play what they have to get in the ballpark, the do more research from there. Like "I want a Big Muff with flatter mids to cut through the mix" or "I want a Tube Screamer that has more output to push the front of the amp, and is a little fuller in the bass".
Our good buddy GearJonser has wisely pointed out, it's all about matching your gain pedal to your guitar and more importantly your amp. Have fun on your quest, and don't make it more complicated than it has to be.
