connecting audio shield headphone output to my amp?

[dentaku]

I see the warning on the back of the Audio Shield about not shorting Vgnd and Gnd. I'm still not sure what Vgnd is.
If I plug in a 1/8" cable from the headphone output to my amplifier aren't I doing just that. The sleeve on the TRS connector is being connected to the GND of the amp which is the same as the GND of the USB in the end.

Am I correct in assuming this or is it OK to connect the headphone output to my amp?

Line out works fine but it's annoying not having control over it's volume as easily as it is with the headphone out.

 

[Theremingenieur]

VGND as its name says, is a virtual GND, only for the headphone output with a DC offset of about 1.7V to save the huge output coupling capacitors. By connecting VGND to GND, you will short these 1.7V and put the SGTL5000 into trouble, it is a clear DO NOT. There are line outputs on the audio board which allow connecting an amplifier without risk. If you want volume control, add a mixer object to your code. Or DOUT the classic way: Add a 22k stereo potentiometer with log characteristic.

 

[dentaku]

VGND as its name says, is a virtual GND, only for the headphone output with a DC offset of about 1.7V to save the huge output coupling capacitors. By connecting VGND to GND, you will short these 1.7V and put the SGTL5000 into trouble, it is a clear DO NOT. There are line outputs on the audio board which allow connecting an amplifier without risk. If you want volume control, add a mixer object to your code. Or DOUT the classic way: Add a 22k stereo potentiometer with log characteristic.

OK, that's what I figured.
Thanks