Open the project enclosure so that you have clear access to the inside of the box. Decide where on the project enclosure you would like to mount your connectors and switch. Make sure you leave enough room between connectors to work while you make solder connections, and make sure you leave adequate space for the audio transformer to be mounted inside the project enclosure once all three connectors and the switch are in place.
Determine the correct mounting hole diameter for the panel-mount switch and XLR and phone connectors. Do this either by consulting the mounting instructions supplied with the item, or by measuring the diameter of the item and sizing the hole slightly larger than its mounting area width. Mark the center locations of your switch and connectors, and use the step drill to make mounting holes for each of them. Use a small drill bit to make holes for any mounting screws or rivets if required. Mount all three connectors and the switch in the project enclosure. Mark the position of the mounting holes for the audio transformer, and use a small drill bit to make holes for the mounting hardware. Mount the audio transformer inside the project enclosure. Make sure any metal shavings are cleared from the project enclosure before proceeding.
Use labels or a felt-tip marker to label the connectors on the outside of the project enclosure. Label one of the 1/4" connectors "Input," the other 1/4" connector "Through," and the XLR connector "Direct Out." Label the switch "Ground Lift."
Solder a wire from the sleeve solder terminal of one 1/4" connector to the sleeve solder terminal of the other 1/4" connector. Solder a wire from the tip solder terminal of one 1/4" connector to the tip solder terminal of the other 1/4" connector. Solder one of the audio transformer primary wires to the sleeve solder terminal of the Input 1/4" connector. Solder the other audio transformer primary wire to the tip solder terminal of the Input 1/4" connector. Make sure that the wires you soldered from the Input 1/4" connector to the Through 1/4" connector remain connected after soldering the transformer primary wires.
Solder a wire from the sleeve terminal of the Input 1/4" connector to one terminal of the switch. Make sure that the wires you previously soldered to the Input 1/4" sleeve solder terminal remain connected. Solder a wire from the other terminal of the switch to pin 1 of the XLR connector. Solder one of the audio transformer secondary wires to pin 2 of the XLR connector. Solder the other audio transformer secondary wire to pin 3 of the XLR connector. Close the project enclosure, making sure that no wires are pinched in any joints.