if the DAC only exists between the logic board and the analog jack then there is a good chance it isn't being piped back in to the lightning port. Even then, I

if the DAC only exists between the logic board and the analog jack then there is a good chance it isn't being piped back in to the lightning port. Even then, I really doubt an entire pin on the lightning connector is dedicated to analog signal, so a DAC would have to exist on the other end of your lightning cable anyway; I suspect this is where your difference in quality come from.