allows switching between a "TS9" mode, in which the circuit and all relevant component values are identical to the vintage model, and a "Hot" mode, which introduces an additional gain stage. Yet another variant is the Ibanez ST9 Super Tube that features a fourth knob ("Mid Boost"), which provides a harder attack. JRC4558D op-amp Much has been made of the operational amplifier chips used in the various versions of the Tube Screamer pedal, and several "fairy tales" about the merits of these devices have been written on the subject. The JRC4558D chip is well-regarded by some. The (RC)4558 is a low priced, general purpose dual operational amplifier, introduced mid 70s by Texas Instruments as an "improved" version of the early 741, and used in thousands of consumer and industrial designs. In fact, JRC4558D is nothing else than the licensed product manufactured by , and identical to any other 4558 chip. Other popular chips used included the TL072 (a JFET input type, highly popular in 80s), "original" TI RC4558P, and OPA2134. The TA75558 (yet another version, made by Toshiba), standard in the TS10 alongside the 4558, is strangely regarded as the "ugly duckling of TS opamps". In reality, the type of op-amp has little to do with the sound of the pedal, which is dominated by the diodes in the op-amp's feedback path. (See Op-amp swapping.) Notable users The pedal was popularized by Stevie Ray Vaughan and Lee Ritenour. Phish guitarist Trey Anastasio implements two TS9 Tube Screamers in his rig. Gary Moore used the TS9 predominantly for 30 years which was key to his signature lead guitar sound. It is widely used in genres as diverse as country, blues and metal. The Tube Screamer has since spawned many clones and modified versions. Possible modifications include use of mismatched, or different diodes (for example, a silicon and a germanium device), or more than two diodes in various arrangements, or modified tone circuits. It is also used by many metal guitarists before the lead channel of the high gain amps to make distortion more focused and to cut the low end. Notable modifiers of the pedal include Robert Keeley of Keeley Electronics and Mike Piera of AnalogMan. Joan Jett used a TS9DX model. Arctic Monkeys frontman Alex Turner Also used an Ibanez Tube Screamer for the band’s second Album: Favourite Worst Nightmare References External links The Technology of the Tube Screamer Tube