anti clipping circuit

Hey all, This is my first post but I've been reading (and learning) a LOT here. :) Here's what I'm wondering about (that I can't find the answer to). One of the amps in my car boasts an "Anti-Clipping Circuit" and I was wondering how that works. The only way I expected it to work was by stopping the volume from going any higher at a certain point, but it doesn't do that because (admittedly, drunk) testing has proven that it can go loud enough to be distorted quite badly. So if it's not that, how DOES it work? The amp is a Proton 222 (I know, it's more than 20 years old. I got them free from my dad's old system.) Thanks in advance for your help guys. :)

"Anti-clipping" is a bit of a misnomer, really. "Soft-clipping" is more correct. It monitors the input signal, and if it sees that the rails are going to be the limit for the output signal, it gently limits the outout signal by "rounding off" the input signal. Rather than a square wave, hard clipped output wave, it is a truncated or shortened sine wave. It does not work "no matter how hard you push", it is most effective AT onset of clipping and slightly beyond. Beyond that level/limit, you can certainly drive the amp to hard clipping, as you have described.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."