Help with Reverse Engineering simple Audio PCB - ESD Protection and Filter

[NNeerr00]

Hi everyone,

I’m pretty new to PCB design and reverse engineering, and this is my first attempt at trying to reverse engineer a part of a PCB. So far, I’ve managed to trace out a portion of the schematic (see attached picture and schematic), but I could use some help moving forward.

What I’ve found:
    - The section seems to be a filter circuit with an L-C combination.
    - Component SX603 looks like it might be an ESD protection diode.

My questions:
How can I figure out the values for:
    - C600, L600, C601, L601, and SX603?
    - What’s the purpose of the 0-ohm resistor in the circuit? I’m seeing one here, but I’m not sure why it's used.
    - Why is the ESD diode only placed on the tip and not also on the ring of the connector? Is there a design reason behind this?

Any advice or guidance would be greatly appreciated, especially since this is my first time trying something like this. Thanks in advance for your help!

[m k]

For component values you need a substitute circuit for calculations and place unknown components there, one at the time.

There's a place for SX600, but component is missing.
So it has had an intention to be there sometime in the past.

To where is 0R connected?
There are big traces around, maybe it's shorting the other side to GND and making the thing mono.

Usually 0R is a simple jumper, or two when other trace goes under it, like SX603.