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).These came in narrower boxes without battery covers.
The TS10, Tube Screamer Classic, is the original Tube Screamer that Ibanez became famous for. It features a Drive control to vary the intensity of the distortion, a Tone control for equalization, and a Level control that varies the overall gain when the distortion is engaged.
SRV used the Tube Screamer to drive his amplifier – either a Fender Vibroverb or a Dumble Steel String Singer, depending on accounts.
The boost gain of the TS-808 pushed the amp to new levels of creamy distortion, adding a grit, a bite, a scream. It was a unique tone, one that SRV cooked up, tasted, added a bit more spice, then adjusted again to create what became his trademark sound on his trademark solo on his trademark song.
Some guitarists prefer this sort of equalization, as it helps to keep their sound from getting lost in the overall mix of the band.
The pedal was produced with many variants: The Tube Screamer pedal was preceded by the orange "Overdrive" (OD) and green "Overdrive-II" (OD-II).