The Tubescreamer is probably the most built overdrive pedal in the DIY community. The pedal has a characteristic mid-boosted tone perfect for soft rock and blues. Also, for rock and metal, it can be used before the lead channel of amplifier to make distortion more focused and to cut the low end. The Tubescreamer has many clones and modified versions.
The pedal has a drive knob, a tone knob, and a level knob. The drive knob adjusts gain, the tone knob adjusts treble and the level knob adjusts the output volume of the pedal. The pedal is used to try to mimic the sound of a vintage tube amplifier. The classic Tube Screamer sound includes a "mid-hump," which means that the circuit accentuates frequencies between the bass and treble ranges (mid-frequencies). Some guitarists prefer this sort of equalization, as it helps to keep their sound from getting lost in the overall mix of the band. (from Wikipedia https://en.wikipedia.org/wiki/Ibanez_Tube_Screamer)