TDA7376B AMP with balanced inputs
 

Hi everyone,
I'm making a small 40 watt amplifier and an unbalanced to balanced circuit so I can run home audio through my house.

I am having trouble with the unbalanced to balanced circuit. My schmeatic is shown below: http://sound.westhost.com/p87-f3.gif

To start off I am testing these circuits using the headphone jack from my computer. The trouble I'm having is that there is such a large gain that I need to keep my volume level at about 2/100 to prevent my the amp from overdriving the speakers. What resistor pairs do I need to change to decrease the gain factor? Also when I remove the audio jack from my computer the speakers emit a loud buzzing noise that only exists when I use the Op amp circuit to deliver the balanced signal. If I just take the unbalanced from the headphone jack to the amp circuit (as shown in the TDA7376B datasheet) and remove the headphone jack there is no buzzing noise. Any ideas as to where this buzzing is coming from? Power supply maybe? I'm jsut using a 9V wall wort with a virtual ground to provide ~ +/- 5V and 2 1000uF caps across each terminal.