Ibanez Tube Screamer

The Ibanez Tube Screamer is an overdrive effect pedal produced by Ibanez which is named for the fact that its light distortion is similar to the sound given by overdriven tube amps. The pedal's sound is different from most distortion pedals as the waveform is compressed with little loss of the original signal, creating a full bluesy tone.

Description

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 preamp tubes into an overdriven state. The classic Tube Screamer sound includes a "mid-hump," which means that the circuit accentuates freqencies between the bass and treble ranges (mid-frequencies). Many 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 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, TS-7, and TS-5 are less collectible, but contain a nearly identical underlying circuit. The TS-9 and TS-808 pedals have been reissued, but not all of these reissues are using the same parts (chips) that helped to shape the famous tubescreamer sound. Some musicians are having a technician perform modifications to the circuit to improve the sound. In addition, a number of other effects manufacturers make versions of the Tube Screamer circuit, including Maxon (who produced the original Tubescreamer pedals for the Ibanez brand in the seventies and early eighties). In addition, many of the most highly-regarded overdrive pedals, both mass-manufactured and boutique, owe their heritage to the Tube Screamer circuit.

Because the Tube Screamer produces symmetrical clipping, its tone may be associated with a vintage characteristic. Other overdrive pedals such as the Boss SD-1 clip the waveforms asymmetrically, which has been said to result in a more tube-like overdrive.

Effectively, what the Tube Screamer actually does is overload an amplifier's preamp circuit with an artificial amount of gain. 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.

Design

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." As well, Tamura added a "Post-clipping equalization circuit" with a "first-order high-pass shelving filter" that "is linearly dependent on its gain", an approach called "progressivity." http://www.bteaudio.com/articles/TSS/TSS.html Tube Screamer’s Secret

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. Later versions include a "Hot" mode, which modifies the circuit slightly to produce higher gain sounds. The TS-7 is notable for this, since it allows switching from "Classic" (i.e., TS-808 or TS-9-like sounds) to "Hot" mode.

Much has been made of the OpAmp (operational amplifier) chips used in the various versions Tube Screamer pedal, [http://www.analogman.com/tshist.htm AnalogMan] has written a history of the tubescreamer 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. The Tube Screamer uses electronic FET switching.

References

External links

* [http://www.geofex.com/Article_Folders/TStech/tsxtech.htm The Technology of the Tube Screamer]
* [http://www.analogman.com/tshist.htm Tube Screamer History on Analogman.com]
* [http://www.bteaudio.com/articles/TSS/TSS.html Tube Screamer’s Secret]