The battery snap is the last part to be installed. The red lead goes into the hole marked with a “+” sign and the black goes into the
That’s it! But wait, before you grab a battery and fire up your kit let’s check a few things. Mainly check the orientation of the ICs, diodes, and all those electrolytics. We don’t want anything to go “pop” when we apply power, right? Also check your solder joints for any that are less than perfect and make sure that all the solder connections you see on the back are supposed to be there. Bridges can be dangerous to your circuit. Be sure none of your clipped off wires have lodged between the connections on the back. When you’re satisfied we’ll move on and give your headphone amp a try.