Another Noob Question: Clipping & Headroom

[sprog]

I'm on a mission to fully understand clipping. I think I'm getting closer, but the more I learn, the more I realize that I don't have a clue. 

Anyway, I have been reading about rail-to-rail opamps and the increased headroom they offer. Question: is this only if they are used as a clean boost? Doesn't clipping squeeze any amount of voltage to the same output, making 'headroom' a non-reality in od/dist effects? Or is this only if the clipping is on the output side.....? I guess clipping in the feedback loop would not really affect headroom.... I don't really know. Anyone shed some light on this?

[aron]

Clipping means that your signal is now distorted and you have no more "headroom" since you are clipping. It's like when you record and you have the input level too high. It's distorting because you have run out of headroom - your signal is no longer "clean".

[sprog]

Thanks, Aron. So, I guess the rail-to-rail opamp's extra 'headroom' is not really true then, if the clipping is on the output side going to gnd, right? If it's in the feedback loop, I can see it still having more dynamics. Am I thinking correctly here? I hope so, 'cause it's beginning to make some sense.

[slacker]

Normally with a diode to ground clipper like a Dist + the opamp its self is producing some distortion and clipping before the signal gets fed to the diodes so not all of the clipping is from the diodes. You can test this by removing the diodes and turning the gain all the way up, you'll still get quite a lot of distortion.
If you used a rail to rail opamp the signal would have more headroom in the opamp section so a signal with the same amount of gain applied would be cleaner than in a normal opamp. If you feed this to the clipping diodes you'll get a different sound than feeding them a distorted signal of the same volume.

Another reason for using rail to rail opamps is because when they do distort it is a softer/nicer sound than a normal opamp so you can use them for disortion pedals on their own without using any clipping diodes.