This app note was used to develop the program used to make the following screen shot data.
The cap goes from input to ground and the coil is in series with the head phones. I assumed 2K phones for the sim.
This is the frequency response. As frequency increases the coil rejects and the cap passes the signal.
I've got the set half wired. The choke is already in place.
After I get the set working I'll try the cap using clip leads.
You've got your ARF settings so that I can't reply there. Something about disabled private message receipt