If I do not connect the ground wire to the phono stage, the sound is reduced but it is still there. Any more ideas?
Ssayeed,
Did you try to connect the ground to the chassis of the integrated amp? Maybe a screw on the bottom of the amp.
Have you check for proper AC polarity orientation?
Sometimes that can cause a buzz. Maybe the amp is crossed....
http://www.boundforsound.com/tweak.htm
http://www.gcaudio.com/resources/howtos/acpolarity.html
and then there is this.
http://www.jensen-transformers.com/an/an004.pdf
http://www.jensen-transformers.com/an/generic%20seminar.pdf
Just grabbing at straws..... Have you tried unplugging the TT from the AC power receptacle and checked for buzz?