I am not sure if this is possible in WP8, but I am trying to tweak the audio playback settings and would like to know if anyone else has been able to accomplish this.
What I am looking to do is have the phone enter a "silent mode," where absolutely no sounds will emit from its speakers, yet retain a volume setting so that if I plug in headphones or an audio cable, it will still output sound across the wire.
Currently, even with my phone on vibrate, I have to hold down the Lumia 920's side rocker switch to bring system volume all the way down to zero if I want the phone to be truly silent. When I want to listen and plug in a cable, I then have to bring the volume back up.
If I forget to bring the volume back down when I am done listening, and then launch a games or another app with sound, the app will play sound out of the phones speakers when in vibrate mode with no headphones plugged in.