I’m an Amateur Radio operator, and I have been setting up a new radio. This radio IC-7610, has an inbuilt USB serial port and soundcard,
When setting up the sound system to take audio from the radio it’s easy, (Using pulse audio) click on the loudspeaker icon, and select the applications tab. I can then set up the input source (PCM2901) and all is OK, the computer sees the audion from the radio and the decoding software dose it’s job.
The next stage is to send some audio This is for a number of different digital mods such as FT8 SSTV and so on. I could not find any way tio set the output. I tried all the combinations of devices that the software detected with no luck.
I must have spent a couple of h ours going around in circles trying to solve this. Out of desperation - and the swear box was getting full - 
I opened up the setting (loudspeaker icon on taskbar) and pinned it to stay open.
When I then sent some test audio, the application appeared in the pinned open window and the appropriate output device could be selected. As soon as the test stopped, the application promptly vanished from the window.
So in normal use you would send a test, find it does not work, open the sound window and see nothing. Frustrating to say the least.
I think this behavior is a bit crazy . The system already knows that the application is using some hardware for sound input, so why is the sound output not displayed at the same time.
Andy
Operating System: Debian GNU/Linux 12
KDE Plasma Version: 5.27.5
KDE Frameworks Version: 5.103.0
Qt Version: 5.15.8
Kernel Version: 6.1.0-26-amd64 (64-bit)
Graphics Platform: X11
Processors: 8 × AMD FX™-8350 Eight-Core Processor
Memory: 15.6 GiB of RAM
Graphics Processor: VERDE
Manufacturer: Gigabyte Technology Co., Ltd.
Product Name: GA-78LMT-S2P