Strip 1 inch of shielding from each end of an XLR cable using a pair of wire strippers. Strip 1/4 inch of insulation from each of the three inner wires.
Remove the screw from the XLR connector with a flat-head screwdriver, and slide out the inner connector from its casing.
Solder one of each of the three wires to the three numbered contacts of the XLR connector. Make a note of which color wire is connected to which numbered connector. The connector numbers are stamped next to the base of each contact.
Solder the wire connected to the number 2 XLR contact to the tip contact of the RCA connector. The tip contact is the shorter of the two contacts.
Solder both the wires connected to the numbers 1 and 3 XLR contacts to the sleeve contact of the RCA connector.
Replace the XLR connector's casing and secure it with the screw using a flat-head screwdriver. The casing only slides onto the XLR connector in one position, as it is slotted to match a groove on the inner part of the connector.