Just built my Piarcade arcade cabinet and installed a 12.1" monitor in it today - had it for a week. After installing the new monitor I am having problems with the sound - when I hold the volume up the sound goes up in volume - I let it go and the volume decreases until there is no sound. Even if I disconnect the volume down button from the picade it still goes down.
If i pull the cable out 1/2 way then the sound stays on but the interference is so much it is not usable. Really disappointed :(
I'm not clear what connectors you are using where, can you describe the audio path in mkre details, from the Pi to your speakers?