I built a Line Out Box. See pics and illustration below. The reason for this build is to run delay-based effects into a secondary amp and to play a no master volume plexi at bedroom levels. The transformer based design seems to work and gives a transparent guitar signal. The problem is the hum. It's not loud but it's there. I placed a ground lift switch in but regardless of it being engaged or not I still seem to get a hum. Can someone please look at my design and verify if the wiring is correct. Have I created a ground loop somewhere? Is there something better I can do?
(http://i1057.photobucket.com/albums/t392/johnnybgooode/line_out_box_pics_zps75871084.jpg)
(http://i1057.photobucket.com/albums/t392/johnnybgooode/lineout_w_phaseampground_zps3b412b58.jpg)
(http://i1057.photobucket.com/albums/t392/johnnybgooode/LineOutBoxforSlaving_zps9a2874ba.jpg)
Your box is not grounded! (there needs to be a physical wire-connection between signal-ground on one of the jacks and the enclosure, so that it can serve as a shielding. Otherwise the wiring inside, and especially the transformer, will pick up hum). You can possibly clamp a piece of bare wire around the shaft of a switch, so that it securely touches the enclosure. Solder the other end to one of the ground-lugs of a jack).
Thanks! Connected a ground wire as suggested and the box is now much quieter.