Notes

The OD-3 is the one of the best overdrives Boss ever created in my opinion, I actually think it's one of the best OD boxes that currently exist on the market. The sound of this pedal is very musical and pleasant, not plain like with many stomp boxes out there. It really sounds smooth, warm, tube-like.

Albeit the manufacturer stated it has a dual-stage overdrive circuit, when I took a look into the OD-3's schematic it seemed to me it had even three clipping cascades, each next one slightly overdrives already overdriven sound that comes from a previous cascade (although I don't consider myself an expert in the electronic field).

The part of the circuit that participates in the clipping (and mostly the whole pedal) consists of discreet components: transistors, resistors, capacitors, and diodes.

A couple of op-amp ICs are used after the clipping stage though.

The range of overdriven sounds I got from my Boss OD-3 pedal varies between just a warm boost to a non-aggressive crunch that I found useful for playing soft-rock and some classic rock tunes. Because this pedal reacts well to attack level of the plectrum, for punchier tones try to pick the strings harder.

Example Settings

(position is indicated in space relative to the numbers on a clock's face)

Typical overdrive sound: 
level = 11:30, tone = 12, drive = 12

Booster:
level = 5, tone = 11:30, drive = 7

Crunchy Rhythm Tone (bridge pickup): 
level = 11, tone = 12, drive = 3

Smooth, Melodic Lead Tone (neck pickup): 
level = 11, tone = 2, drive = 2