Overdrive

Amp distortion in which the waveform is compressed and rounded rather than sharply clipped, adding harmonics while preserving the basic shape of the signal.

The characteristically warm, singing quality comes from soft clipping plus the natural compression of a valve stage, so notes sustain and the sound thickens without becoming harsh. It is a matter of degree rather than a category: push the same circuit further and it becomes distortion, then fuzz. A guitar's volume control changes how much signal reaches the clipping stage, which is why an overdriven amplifier cleans up as the knob is rolled back.

Example: a valve amp at the edge of breakup keeps the body of a chord intact while adding a fibrous, grainy edge to it.

Overdrive

See also