As you know, almost all profesional audio equipment use Balanced (+4dBm) Output. However, almost all FM Exciter have UnBalanced (-10dBV) MPX Input.
The problem is, almost all High-End Soundcards have Balanced circuit for their Input/Output connection.
I think, only ESI Juli@ soundcard that can use Balanced Input, but UnBalanced Output also can be operated, simultaneously. (thanks to Leif for this information 😀 ).
So, you need "Balanced-to-UnBalanced" adapter, and it can be made with very simple "tweak", illustrated as follow…
Pin 3 (Cold) jumper, don’t really needed, because all Soundcard Balanced Output, produced by OpAmp ICs – not from balanced output transformer (such as Lundahl or Jensen).
Balanced connection using TRS connector
VBR,
Ferry