Hello, I have a sound issue on my Oculus rift S. The sound is weak even i set the volume to 100% in most applications. And there does not seem to be any problem when I plug in a headset.
According to my experience the volume 100% on Rift S is similar to the volume 10% on Rift CV1. There was a software update to improved this (1.38). But the audio quality still bad and volume still very weak. I bought a pair of on-ear clip earphones and mount them on headset to fix the audio.
I purchased Klipsch R6 II earbuds and they sound fantastic with the Rift S. I actually prefer earbuds myself anyway so that option worked out well for me.