Passive box to connect 3 stereo outputs to pair of monitors

Hi, I have 3 stereo sound-sources in my home studio:

• a sound card with an analogue output + a mini jack spdif (48000 Hz) output


• a sound card with an analogue output + an RCA spdif (44100 Hz) output


• an analogue line out

I want any of their outputs to be connected to one pair of monitors. Preferably using a passive box / audio-interface / controller. Any recommendations?

Passive box to connect 3 stereo outputs to pair of monitors