Introduction: Dieselpunk Stereophonic Amplifier

About: I also go by the Instructable user name: UnknownUser2007

Every so often projects start out simple but end up taking way more time than first anticipated. Here is one of those projects that got out of hand. My original intent was to make a small, simple, powered speaker box. Nothing fancy, just a low power amp, used computer speakers, all housed in a tiny container. I had no plan to make a "themed" project.

During fabrication, the project seemed to take on a life of its own. After I fab'd the speaker grill, it simply looked like it came from the 1950s. It reminded me of an old Collins ham radio. So instead of steampunk, which I've posted before, the Dieselpunk Stereophonic Amplifier was created.

A couple of highlights...
The typical DC power connector and headphone jacks are hidden behind screw-on caps. The power indicator is made to look like a fuel level gauge and contains REAL 5W-30 motor oil! When connected to AC power it gives off a 60hz hum. That was unintentional but it adds to the Dieselpunk feel. The box is painted in hammertone and aged to give it a greasy Dieselpunk look.

Counter sink bit
Hack Saw
Belt Sander
Hot Glue Gun
Soldering Iron
Dremel Tool
Clothes Pins
Center punch
Stepped drill bit

2 Watt Stereo Kit - Carl's Electronics P/N K115
Small Lunchbox - Michaels
Two - Speakers - salvaged from old computer speakers
Two - 12 inch long brass rods 1/16 inch dia. - Hobby Shop
12VDC Power Transformer
Two - 1/4 FLR x 1/8 FPT brass elbow - Orchard Supply Hardware (OSH)
1/4 inch and 5/16 inch brass compression joints - OSH
Two - Chains - Goldmine Electronics P/N G15272
Toggle Switch - OSH
Rubber Toggle Switch Boot - Goldmine Electronics P/N G16872
6 x 18 inch Sheet Aluminum 0.025 inch thick - OSH
Aluminum Perforated Sheet 0.063" (0.125" holes-0.1875" stagger) 3003-H14 12 inches x 24 inches - Online Metals
1/2 inch angle aluminum - OSH
1-1/2 inch dia. Flange - Weird Stuff
3.5mm Stereo Jack - Radio Shack P/N 274-274
DC Power Jack - Radio Shack P/N 274-1577
DC Power Plug - Radio Shack P/N 274-1569
9V Battery Snap Connector - Radio Shack P/N 270-324
Red LED - Radio Shack P/N 276-330
LED Resistor 560 ohm Radio Shack P/N 271-1116
Perfboard - Radio Shack P/N 276-148
6 AA Battery Holder - Digikey P/N BH26AASF-ND
Foam Rubber - Recycle Bin
1/8 inch masonite board - Scrap Pile
Acrylic tube 3/8 inch OD - Tap Plastics
Six 1-1/4 inch long mounting bolts and nuts 6/32
Various nuts and bolts with tapered heads
Old pot lid knob - Thrift Store
Silicone sealer - OSH
Scrap sheet plastic for the nut retainer - Recycle Bin
Clear label for printer - Office Depo
Gray hammertone spray paint - OSH
Silver spray paint - OSH
Plumbers strapping tape - OSH
5-Minute epoxy - OSH
Crazy Glue - OSH
Paint thinner
Black enamel paint (nail polish) - wife's drawer

This Instructable is medium to high level. Please take the appropriate safety precautions when using any tools. Once, I almost cut my thumb off with a simple coping saw. So, be careful!

Step 1: Make: the Stereo Kit

This is the simple and fun step.

Build the stereo amp per the instructions. The exception is not to solder the volume potentiometer to the board. Also there are gold connection pins that can be excluded. Instead, wires will be soldered directly to the board during the final assembly. However, it is recommended to temporarily wire up the pot to test the circuit.

Step 2: Make: the Box

Place the speakers within the box. Make sure there is enough room for the amp. Trace out a border for the speaker opening. The opening must be larger then the speakers. With a Dremel tool cut out the opening in the box. The Dremel tool leaves a clean cut compared to tin snips. Grind down the edges of the cut so that it is even.

Using the 1/16 inch brass rod, form an edge around the speaker hole. To do this, gently bend the brass wire around a cylinder-shaped object to get a smooth radius around the corners. It took two pieces of wire to make it around the full circumference of the speaker hole.

Next, solder the brass rod to the box. It helps to hold the rod in place with some clothes pins while soldering. Using solder flux helps too.

Finish the hole by filing and sanding the edges.

To give the box a more industrial look, drill holes into the handle. Measure then centerpunch for 5 evenly spaced holes. Use a stepped drill bit to incrementally enlarge the holes. It it easier to keep the holes aligned by slowly enlarging them.

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. 

Step 4: Make: the Connectors

The special connectors are plumbing compression joints. The joints are sold in packages with two nuts and a joint with threaded ends.

This project requires two sizes because the DC power jack and stereo jack are different diameters. 5/16 inch joint for the DC jack and 1/4 inch for the stereo jack.

Cut the 1/4 inch  joint in half with a hacksaw. With a drill, bore out the joint with a 3/8 inch diameter it. Next, take the headphone jack and grind down the diameter so that it will fit inside the bored joint. Solder the jack into the joint.

Repeat the process for the DC power jack.

Find a location for both connectors on the lid of the box. Centerpunch then drill holes for these new connectors. Solder these connectors onto the lid of the box.

The nuts (connector covers) are attached to the box via a chain and retainers that slip over the threaded brass joints. The chains come with a brass fitting. Hack saw off an end of these fittings. The fitting and nut can then be attached to the chain.

The other end of the chain is attached to a retainer that must be fab'd. They're made from plumbers strapping tape and are teardrop shaped. Cut out the shape and drill out larger hole with a stepped drill bit. Cut the chain to length then attach the chain to the retainer.

Next, to keep the chain retainer from falling off the threaded brass joint, fab a plastic washer. The plastic washer must tightly fit on the threaded brass joint. Find some thin plastic in the recycle bin. Using tin snips, drill then cut out the washers. Alternatively, a rubber O-ring can be used.

While working on the lid, now would be a good time to fab the bass vent. The bass vent is more decorative than functional. It consists of a flange and grill. The flange is a piece of "junk" found at a recycler store. It had a lip that was cut off. This particular flange will be near impossible to find/buy but there are substitutes. The first that comes to mind, is a cast iron plumbing flange. Or one could be fabricated from scrap masonite or sheet plastic.

The placement of the flange is not critical. Mark a spot on the lid and cut out a hole. The bass vent grill is cut out from the perforated sheet aluminum.

After making the bass vent, I thought it would be a good effect to back light it with a red LED. This simulates the glow of a vacuum tube. A daughter board was built from scrap perfboard. A 560 ohm was placed in series with the red LED on the board.

Step 5: Make: the Power Indicator

The power indicator is a bit unusual. It was fashioned to look like a sight fuel level gauge (think of commercial coffee pots). Yes, sight fuel level gauges are usually vertical but there wasn't an area available to do that.

The indicator consists of two brass elbows found at the hardware store, a red LED and a 3/8 inch OD acrylic tube. Bore out the ends of the elbows with a 3/8 inch bit. Cut about 1-1/4 inch long piece of acrylic tube. Seal one end of the tube with silicone sealer or equivalent. The other end will be "sealed" with the LED. This step takes a bit of tweaking. Trial fit everything, file, sand, repeat until it is perfect.

For final assembly of the power indicator cover the LED leads with shrink tubing to insulate it from the side walls of the brass elbow. Find some motor oil and add it to the tube. Clean the surfaces then glue the LED onto the end with silicone sealer. Once that has dried, attach the brass elbows and fill the ends with more silicone sealer.

Now that the power indicator is finished, mark a location on the box and drill the holes for it. Position it so that the box handle does not hit the acrylic part but instead hits the brass elbow. It would get very messy if the handle cracked the acrylic!

Now would be a good time to locate and fit the power switch. Find a location for the switch that also clears the handle. Also make sure it clears the speakers, amp and top layer/compartment divider inside of the box. Centerpunch and drill the hole for the switch.

Step 6: Paint

Clean all surfaces and parts with a tack rag. Mask off the back of the connectors and other parts you don't want painted like the handle. Lay a coat of primer. Sand to a smooth finish. Next comes the final color painting. Paint the overall box hammertone. Paint the speaker grill, brass nuts and brass elbows silver. Flat black was used on the nut retaining chains, top layer compartment divider and bass vent grill.

Want Steampunk? Instead of a Dieselpunk theme you can select a color scheme to make your box look more Steampunk. For example, instead of gray hammertone, use bronze hammertone. Paint the grills gold and leave the brass parts as is. The choice is yours!

Step 7: Final Assembly

This last part consists of putting it all together and adding some finishing touches.

Wire the lid. The DC power and line-in go straight to the amp board. Make sure there is enough slack in the wires so that it doesn't bind as the lid opens and closes. Wire up the speakers. Pay attention to the left and right channels. Install the volume potentiometer.

The volume knob is from a knob from an old pot cover. It was shortened and bored out 1/4 inch bit to fit the pot shaft. Use hot glue to attach the knob to the shaft.

Next make the name plates. The nameplates are printed clear labels on 0.025 inch aluminum sheet. The plates are a chance to personalize the box. Attach the plates with Crazy Glue.

The V-emblem fills empty space on the grill. It is made from 1/2 inch angle aluminum. Using a hack saw, cut two pieces of aluminum at an angle. Using a file and or belt sander, finish them so they form a V-shape. Use masking tape to temporarily attach the two ends together. To permanently attach the two ends together take a piece of wire and form it so it fits inside the V-emblem. Place the emblem so that it sits level. Mix up some 5-Minute epoxy. Fill up the V-emblem with the epoxy. Let it sit over night. File and/or sand the emblem. Give the emblem a texture by lightly sanding the surface. Hot glue the emblem to the speaker grill.

The final touch is to age the box. Start by brushing black enamel in the edges and crevices.
It is okay to get messy. Next take paint thinner to remove and blend the black enamel to simulate grease.
Repeat until happy with the look.

Don't like the buzz? During the final assembly, I found that the DC power transformer was "emitting" a 60Hz buzz. Rather than build a notch filter, I decided to leave it. Another option is to run the amp from batteries. Use a 6 AA battery holder and connect up the 9V battery clip and DC Power Plug. Use this set up instead of the power transformer to eliminate the buzz.

Congratulations! You finished! :) Thanks for viewing my Instructable. I hope this project stirs up the creative juices for other Makers!