Try tanh function mapped to the range of about -5 +5 and a small signal input. http://mathworld.wolfram.com/HyperbolicTangent.html
Here's a nice approximation with five multiplies http://www.musicdsp.org/archive.php?classid=5#238
what's the best and most cpu efficient way to clip a signal in an analogue fashion, rather than getting nasty digital distortion?
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