Mono input to Stereo output passive adapter with isolation

[neazoi]

Hi, I have a receiver with mono output (shortwave RX) and I want to connect it to the stereo input of the sound blaster but also isolate the two systems. The classic way is to do it using an 600R:600R isolation transformer.
However I have seen this schematic https://antiqueradio.org/art/iPodAdaptorSchematic.jpg from this page https://antiqueradio.org/iPodAdaptor.htm it is intended for the othr way round, to accept stereo input and convert it to mono.
However I thought if this phasing of the transformers could be used to isolate the two sound blaster channels.


Also I have seen this https://78462f86-a-6ea0e638-s-sites...sWQ-4ZPxkFH2JpZNvSoPtIxLd5quI=&attredirects=0
Although it is a mono to mono connection, I was wondering what these PI filters do?

Also any other ideas would be helpfull, the only limitation is that this adapter has to be passive.

 

[erikl]

If the stereo input of the sound blaster has a sufficiently high impedance, simply use 2 high-ohmic series resistors for each stereo input. Say 10..30% of the input impedance.

 

[FvM]

Driving a stereo input from a mono signal is done by connecting both L and R terminal.

In so far there's nothing special with driving a stereo input by your circuit. All other points like isolation or RF filtering apply just the same.