CATEGORY: OVERDRIVE PEDAL
BY CHRIS GILL
BOSS INTRODUCED THE SD-1 Super Overdrive pedal way back in 1981. Since then, the SD-1 has remained in continuous production, selling literally millions of units and consistently enjoying status as a top-selling pedal for several decades, not just within Boss sales but in general overall pedal sales as well. The reasons for its success are pretty simple: it’s inexpensive (brand-new ones sell for less than $70); it’s incredibly sturdy and reliable; and it just sounds good. Thanks to the SD-1’s long history and incredible success, there’s a very good chance that most guitarists reading this article already own or have owned one.
Boss developed the SD-1 as an improved version of the OD-1 Overdrive by adding a tone control and making a few tweaks to the circuit. Tone snobs can wax poetic about how certain component changes over the years have affected its tone, but the truth is a new SD-1 doesn’t sound dramatically different from an original early Eighties model, and many players may actually prefer the nuances of newer units. The key to the distinctive overdrive tones of these Boss overdrive circuits is asymmetrical clipping, which is the result of when a signal’s waveform has positive and negative amplitude peaks that are clipped unevenly, in the SD-1’s case using a different number of diodes to clip the positive and negative peaks respectively. The end result is similar to the overdrive produced by a tube amp’s push/pull circuit as no two tubes are really ever matched 100 percent.
Asymmetrical clipping produces both even and odd harmonics, resulting in harmonically rich distortion that soun
