A few months ago I built the bassman version of the Ruby headphone amp into an Altoids tin (http://www.runoffgroove.com/ruby.html).
This put me on the constant lookout for project boxes of similar sorts. The can from the illy espresso I'd been drinking stuck out, and I knew it was the right thing for the next version which could also house a small speaker.
The buildout started with the electronics and I wanted to build the amp on to a perf board half the size of the one I used for the altoids amp. As always, soldering all these electronics together can be tedious. The more planning you do prior to buildout the easier the job is. However, if you lack experience in a subject matter (in my case electronics) it takes a certain amount of trial and error to even be able to plan something.
The speaker I bought was about an inch smaller in diameter than the can, so I needed a large "washer" which could bridge the speaker to the diameter of the can. I went through a few iterations. Trying to cut a sheet metal ring resulted in a jaggy nasty thing that cut my fingers up. A CD jewel case was too brittle and shattered when cut. I finally settled on the plastic from a DVD case which was soft yet rigid enough for this purpose.
A tricky part of this buildout ended up being the 9volt battery accessibility. The bottom is a nice logical spot but how would it be housed and accessible? I looked online for plastic battery boxes which could potentially be inserted and slide out for changing the battery. I really could not find anything that would do what I want or the option was over priced. I opted to build my own using sheet metal. The design is to wrap the battery with the metal but have two tabbed edges stick out of one of the sides that could be screwed into the bottom. I first mocked up the design with paper and used it as a template for cutting out the sheet metal. An important part of this was to line the inside with some left over static foam I had laying around. This kept the battery from rattling around.
Cutting out the bottom of the can was done by first drilling holes on the corners and then slicing it up with an exacto knife:
Installing the electronics in the can turned out to be harder than I thought. Since the knobs and jacks were located at the bottom and my hand didn't really fit inside the can very well, it was seriously difficult tightening it all up. I broke wires off the board on more than one occasion. I decided the top of the battery box was also nice location of the electronics board since I could pull the board out fairly easily for potential maintenance.
I wanted to add custom decals that somewhat matched the style of the existing labels on the can. It took about a week of searching and trial and error to find the right type of thing to do the job. I ended up ordering ink jet water slide decals from: http://www.papilio.com These worked great and were far better then anything I found at retail stores (office depot and a handful of hobby/model shops). One thing I did get from a hobby shop was "microscale liquid decal film". I used this as a clear coat after printing the labels.
(labels shown are from a different project)
The instructions that come with the paper are pretty good but here's some extra trial and error I went through.
- Ink only needed to dry for about 15 minutes after printing (these are small labels)
- Microscale film needed to dry for 15 minutes
- Print extra copies of the label as you can easily screw them up when sliding onto objects.
- Use a brand new exacto blade to cut out the labels. Otherwise the edges can stick up a little once the decal is dry.
Some of the thoughts I had in regards to usability of the amp:
- No switches. All functions are triggered by plugging cables into the device. For instance, power turns on when the input cable is in. Speakers are switched to headphones when headphones are plugged in.
- Keep audio jacks at the the bottom of the can. This would keep the can from tipping over when a cable is gets pulled on.
- Knobs should be positioned above cables so that the cable does not get in the way of turning the knob.
- Hide the speaker under the lid.
I also had thought of somehow hiding all the controls under the lid or on the bottom. But this would have been difficult and I think it looks cool with the knobs sticking out the sides allowing the original label to be fully displayed. However, it is a little hard to use this way because the knobs are hard to turn with one hand (using your right arm you have to twist your arm to turn the knob on the left side or vice versa). Having the knobs close together would have been a much better decision as would allow you to easily tweak combination's of gain and output volume to get different effects.