Combine sound for Display port and HDMI

I have an nvidia gtx 1050 running on debian 9. I have 2 external monitors, one through Display port and one through HDMI. Both monitors output the sound just fine, but only one at a time. Is there any way to combine sound for both digital outputs? I tried using Pulse audio preferences to add a virtual device, but that device is a bridger between the "Digital Ouput" (motherboard sound) and one of the HDMI outputs (whichever is currently enabled/active)