Dieselpunk Stereophonic Amplifier

Step 3 Make: the Internal Chassis

The chassis consists of three layers. The first is the speaker grill itself. Next is a masonite layer than holds the speakers and the amp. The top layer creates a secondary compartment area that holds the 12VDC Power Transformer, patch cable and optional battery pack.

From the inside of the box, place a sheet of paper and trace out a pattern for the speaker grill. Transfer the pattern to the perforated aluminum sheet. The aluminum sheet is soft so tin snips can be used to cut it out.

Next, using the same pattern, transfer it to the masonite board. Cut it out with a fine tooth jigsaw. Position the speaker and amp on the masonite board and mark their locations. Make sure you leave room for the volume potentiometer too. Cut out holes for the speakers. Drill and countersink holes for the speakers. Drill and countersink holes for the amp and pot.

Temporarily mount the speakers. Take the top layer and place it on top of the speaker magnets. Mark the location of the magnets and cut it out with tin snips. Remove the speakers and stack all the layers inside the box over the speaker opening.

Next, locate spots for the six long mounting bolts. Centerpunch then drill the six holes from the outside of the box through all three layers. Make the spacers that separate the top layer from the masonite layer.
Cut six lengths of 3/8 inch OD acrylic tubing. The spacers should be about 1-1/16 inch long but that will vary depending on the size of your speakers. Make sure they are all the same length.

Now it is time to fit the power transformer into the compartment area of the box. Temporarily assemble the entire chassis including the speakers. Each 12VDC power transformers differ in size. Find a place within the compartment where it doesn't interfere with other components.The power transformer in this build was too wide to fit inside the compartment. Therefore, it was decided to position the power transformer with the prongs face down. This meant access slots had to be cut into the perforated aluminum sheet.

First, create a template of the face of the transformer including slots for the prongs. Locate, then transfer the template to the perforated aluminum compartment divider. Make sure there will be enough clearance around the transfer when all components are installed. Mark the perforated aluminum where the slots will be located. Use a small file to elongate the holes.

In the final assembly, fit a small square of foam rubber onto the lid so that the transformer will not move around when the lid is closed.