Overdrive

Distortion Confusion

"Overdrive" is a gain-based effect that people often mistake as distortion. It's hard to draw the line between the two, especially regarding guitar effect pedals. One of the simplest ways to describe this effect is to say that overdrive occurs when input gain exceeds the capacity of a device to handle the amount of gain thrown at it, in this case, a tube. What happens is that the smooth waveform that goes into the device gets "clipped." Sonically, we perceive the result of this clipping as distortion. The higher the wave's amplitude, the greater the distortion we hear. There's been a lot of confusion about these two terms. This is because they're used so loosely and often interchangeably.  

Boost Pedal

A way to think about overdrive vs distortion is that overdrive happens in the front end (what you put in) while distortion occurs on the back end (what you hear). But here's where we get into some murky territory, especially with pedals. Suppose we're talking about overdrive as simply overpowering the front end of an amp to make the tubes clip. In that case, the only pedal technically an overdrive is a boost pedal that takes your guitar's signal and ups its voltage. But lots of manufacturers call their pedals overdrive pedals. In reality, most of those are technically distortion pedals. The effect is most closely associated with true amp distortion. It aims to mimic the effect of amp tubes overdriven by high gain.  

Guitar Pedals

Overdrive guitar pedals break up into two categories. First are transparent, mid-scooped boosters, and second, compressed mid-boosted overdrives. The transparent, mids scooped boosters were designed to drive large tube stacks into distortion in the late '60s and early '70s. These pedals can sound horrible on an uncompressed amps. However, they sound creamy and smooth on a compressed and mids-boosted Marshall. Compressed and mids-boosted overdrives started to appear in the late 70s with the Tube Screamer and, later, with boutique designs mimicking the Dumble amp and other mids-oriented amps. These pedals will produce a smoother and overall bigger sounding tone on amps like the Twin and smaller bedroom amps.  

Mild Distortion

Put simply, overdrive tends to be a milder, less linear distortion with a more dynamic response. So, the tone will saturate less when played more quietly. On the other hand, it will distort more when played louder/ harder and apply a mild compression to the tone. In effect, when it starts to overdrive, the signal is soft-clipping. Consequently, the signal is distorted and compressed smoothly and gradually according to how much it has crossed this threshold.