Cut plywood into seven pieces: one 43 1/4 inches by 33 inches, two 12 inches by 43 1/4 inches, three 12 inches by 31 1/2 inches, and one 13 inches by 33 inches. The two pieces that are 12 by 43 1/4 inches are the side pieces, the piece that is 43 1/4 by 33 inches is the back, the piece that is 13 by 33 inches is the top, and the three pieces that are 12 by 31 1/2 inches are the shelves. Make sure you have someone to help you, as you will need two sets of hands.
Hold the two side pieces straight up and down on their short edges. Place the top board across them and line up all of the edges. Attach the top with nails at the corners.
Turn the piece on its face and lay the back piece in place. Align the edges and nail the piece securely at the corners again. Turn the open box you have built right-side-up.
Decide where the shelves should go to fit all of your equipment. Measure out these locations and mark them on the inside of the shelving unit. Pick up one of the shelf pieces and slide it into the unit.
Align the shorter edges of the shelf with one set of height marks. Use a level to make sure that you are holding the shelf straight. Attach the shelf with nails at each corner sunk through the side of the unit.
Install the rest of the shelves in the same way as you did the first. Cut holes in the back as necessary for wires using a hole saw. Paint the shelving unit if you wish, and allow it to dry 12 to 24 hours before installing your media.