My POD HD500x doesn't sound harmoniusly rich when i do the following: 
Phones Output -> Stereo System by using a 1/4"-RCA stereo cable 
  
Sounds like bypass. I'm using the Studio/Direct output, although I've tried the other outputs (Combo Pwr Stack, etc.) and changes a little but stills the same.  
MASTER VOLUME is at half-step. (When I put it 100% it doesn't change either) 
  
I go for distortioned presets and it stills sounds so bad 
  
When I start from the 1/4" R/L Mono output it stills the same. 
  
Cables are fine. 
  
I have the last usb firmware, just in case. 
  
Any thoughs? 
  
Thanks for reading