How do I mute my speakers and listen through headphones with this setup?

[admin_exported]

My setup is:

PC Soundcard (X-Fi Titanium HD) -> Amp (Marantz PM7200) -> Speakers (B&W 603 s2).

Sometimes I want to listen through the headphone jack of the amp but have the speakers muted. I want to use the amp headphone amp as I'm sure it's better than the soundcard jack. How do I do this? If I turn the amp volume down it goes down in the headphones too.

Cheers!

 

[nads]

turn the speakers off. left side 1 speakers 2 buttons out is off buttons in is on.