Looking at the picture I assume you have removed the shield that surrounds the tube and the tube is exposed.
While pulling outward on the tube gently move the tube ever so slightly side to side as pulling the tube out of the socket.
>http://www.digitalaudioreview.net.au/index.php/audio-reviews/digital-source-reviews/item/175-eastern-electric-minimax-tube-dac
While pulling outward on the tube gently move the tube ever so slightly side to side as pulling the tube out of the socket.
>http://www.digitalaudioreview.net.au/index.php/audio-reviews/digital-source-reviews/item/175-eastern-electric-minimax-tube-dac