You have only configured one sound card. Solution: You need two separate stereo outputs. Use a USB sound card as a second output. Configure Player B to use the USB device.
Jazler does not offer a traditional "freeware" download. The software is licensed, but you can obtain the installer in two legitimate ways: Jazler Soho Download
To help you make an informed decision, here is a quick look at the advantages and limitations of this platform: You have only configured one sound card
If you tell me what specific feature you are most interested in testing (like streaming, automated scheduling, or database organization), I can provide a step-by-step setup guide for that module! Jazler SOHO - New Radio automation, reliable and stable or database organization)