How to work out potentiometer value. ASAP!

[superslash1994]

Hey, I'm Louis, I'm 14, and I'm new here :P

Basically, I'm building a 10 channel audio mixer, like you'd typically find in a PA system. Anyway, It's almost finished but I need help working out the value for a potentiometer for the master volume on it.
The image (below) shows the schematic, (although it only shows 8 channels, it's actually now 10) And an arrow indicating where the potentiometer needs to go.
http://i236.photobucket.com/albums/ff22/superslash1994/8channel.jpg

Thanks in advance :D

~Louis

[sparkysi]

Why would you put the pot in the line out stage rather than replace one of the pre load resistors on the amp stage? By putting it on the output you are loading up the signal and will cause losses that will be quite bad.