More from
http://guitar-fx-layouts.42897.x6.nabble.com/Modular-synth-layout-repository-tp33246.htmlHere's the 4 channel mixer
http://castlerocktronics.com/modular/articles/CR-002_-_Output_Mixer.pdfI got a little confused with the output to the master pot so it might be a good idea to check what's going on around pin 6 & 7 in case i've made a balls up
Cheers
Phil