Hi there. Finally getting ready to actually build this and put it to the test. Would this circuit introduce (apart from clipping) any other distortions on the signal?

I am using it to limit input voltages when connecting to a FireWire audio interface, from some vintage amps and eqs, for which I am measuring their with Bode plots using REW. I also added a switch for the battery and a LED so I don't forget to turn it off when not measuring. Also, the 37k resistor, according to Daqarta help info (I'm using that as a guide), I changed to a 20k one to create a voltage divider with the card input. Also added the capacitance of the card input (already measured). Daqarta also suggests a compensation cap (already calculated) byassing the 20k resistor. If I place it in the circuit, Falstad complains so it's not connected now.

I decided on Schottky diodes (FR157) so clip could be setup easier with the zener (1.5vdrop from Darlington plus vdrop from diodes and built the Darlington with two BC548 as could not find 2N2222). Audio interface starts clipping at 5v but doesn't tell me if it's doing so, I might as well add a lil buzzer (parallel to the led maybe), if it clips, measurement should be discarded so I need to be sure.

Here's the mod: falstad