Well, before deciding what they do and designing a switch circuit. If you wonder what they do, unsolder one end of each and lift it out of the circuit. Now you'll know.
An LED has a junction voltage. Seems to me they start at something over 1 volt, and like blue ones up to well over 2v maybe even 3v. I don't mess with them so I am not up to date on current LED types. But until you hit that voltage, they don't conduct, so they only will clip when your signal level gets up to the 1.2v or whatever it is in your case.
Just my opinion, but I suspect they are not there as clippers, they are there as limiters. I could be wrong.
An LED has a junction voltage. Seems to me they start at something over 1 volt, and like blue ones up to well over 2v maybe even 3v. I don't mess with them so I am not up to date on current LED types. But until you hit that voltage, they don't conduct, so they only will clip when your signal level gets up to the 1.2v or whatever it is in your case.
Just my opinion, but I suspect they are not there as clippers, they are there as limiters. I could be wrong.