The Ibanez Tube Screamer is an overdrive effect pedal produced by Ibanez and is so named because its light distortion is similar to the sound created by an overdriven tube amp. The pedal’s sound is different from most distortion pedals as the waveform is clipped and the tone is shaped in a subtle manner creating a mid-humped tone popular with blues players.
The pedal has an overdrive knob, a tone knob, and a level knob. The drive knob controls the level of distortion, the tone knob adjusts the amount of treble in the sound, and the level knob controls the output volume of the pedal. The pedal can be used on a solid-state amp to try to mimic the sound of a vintage tube amp, although many guitarists prefer to use it to push a tube amp’s power amp into an overdriven state.
The classic Tube Screamer sound includes a “mid-hump,” which means that the circuit accentuates frequencies between the bass and treble ranges (mid-frequencies).
The pedal was produced with many variants. The early incarnations of the TS-808 and TS-9 are the most sought after by collectors, due in part to the fact that Stevie Ray Vaughan is known to have used them as part of his signature sound. Other variants, including the TS-10, TS7, and TS-5 are less collectible and vary in the their reproduction of the original circuit. The TS-9 and TS-808 pedals have been reissued, and according to the company, feature the same circuitry, electronics and design components that helped to shape the famous Tube Screamer sound. Some musicians have a technician perform modifications to the unit to change the sound to their liking. Also, Maxon, who produced the original Tube Screamer pedals for the Ibanez brand in the seventies and eighties, produce their own version of the Tube Screamer. In addition, many of the most highly-regarded overdrive pedals, both mass-manufactured and boutique, owe their heritage to the Tube Screamer circuit.
When used with a tube amplifier the Tube Screamer increases the gain of the input signal overloading the preamp and further distorting the signal. When used with a cranked master-volume type tube amplifier, this can result in much higher volumes than before the pedal is engaged if the preamp is not already turned up fairly high. Provided the preamp gain is already turned up, the Tube Screamer will saturate the signal, creating a thickly overdriven tone.
Mr. S. Tamura, the designer of the Tube Screamer, used a subtle clipping circuit to create the pedal’s sound. He mixed the input signal with the output signal of the clipping circuit, which
“preserves the original dynamics of the input signal which otherwise would get lost at the threshold of clipping.”: In this fashion, it preserves the “…original dynamics of the input signal [and] avoids muddiness and vastly improves clarity and responsiveness.”
The circuit uses transistor buffers at both the input and the output. The overdrive is produced using a variable gain op-amp circuit with matched diodes in the feedback circuit to produce soft, symmetrical clipping of the input waveform. The overdrive stage is followed by a simple lowpass filter and active tone control circuit and volume control. This circuit is unexceptional, and the success of the Tube Screamer’s sound probably has more to do with intelligent selection of tone shaping elements (particularly capacitor values) throughout the circuit. The TS7 allows switching between “TS9″, with the circuit and all relevant component values being identical to the vintage model, to “Hot” mode which introduces an additional gain stage.
Much has been made of the OpAmp (operational amplifier) chips used in the various versions Tube Screamer pedal, AnalogMan has written a history of the Tube Screamer that explains this. The JRC4558D chip is particularly well regarded. In fact, the JRC4558D is used in Analogman’s “Silver” modification. Trey Anastasio of Phish fame uses two silver-modified TS-9s on his pedalboard. Other popular chips included the TL072, RC4558P, and OPA2134. The Tube Screamer uses electronic FET switching.
More recently, the Tube Screamer has been become a popular template for custom pedal designs of boutique manufacturers. Variants include many dual opamp circuits with diode clipping feedback loops with the classic “mid-hump” tone made famous by the original TS808 circuit. Many suggest that the Fulltone Fulldrive is closely inspired by the tube screamer. Moreover, increasing numbers of modifications of the circuit have surfaced, including popular mods by Analogman of NYC, Robert Keeley of Keeley Electronics , Brian Wampler of Indy Guitarist, Vodka Mods, CMAT, and many others. Typical mods cover chip substitutions, diode replacments, capacitor upgrades, and tonestack reconfigurations. Many DIY versions of the pedal also exist on sites such as BYOC, General Guitar Gadgets, and many others.
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