Pocket Synth Briefcase V2

Today I'd like to share my experience making an upgraded version of Pocket Synth Briefcase with plastic button caps, a convenient battery tray and an integrated speaker.

I've started by disassembling the setup I've already had, but if you are interested in building something similar from scratch, you can find more info about components and tools I've used in my previous instructable.

The first step was to order a 3PO Case by Dich Studios. The assembly process was really straightforward, but it required some practice and a lot of patience, especially when it came to glueing the buttons together. In the end I was really impressed how big of a difference the 3PO case has made. Totally recommend.

A briefcase with a 3PO case and a MakerHart JustMixer in it can be a very nice minimal setup option by itself. I had been using it for a few months before I decided to continue making further improvements.

Step 1: Planning

My previous setup was great, but of course had some disadvantages. The first thing that I'd been willing to change for a long time was the amount of batteries it used. In total there were 8 AAA batteries and even though they don't usually run out that often, I always had to carry a bunch of extra batteries in my pocket in case if one (or more) of the POs or the mixer dies in the middle of a jam. I've considered using a USB power bank too, but since there is not a lot of room in the case and it needs a step down voltage converter, I've decided to go with a pair of good old AA batteries. The second improvement was an integrated speaker, more of a nice-to-have thing. I also wanted to have a power switch, so that I could be sure that none of the devices can slowly drain the batteries in idle mode (which happened with my POs a couple of times) and an audio output selector between speaker and 3.5mm socket.

I've used Tinkercad to get an overview of how the components can be placed within the briefcase dimensions. For this setup I wanted to try laser cutting, so after I got all components and measured them carefully, I could start drawing a blueprint in SketchUp.

Step 2: Cutting the Panels

I've never done laser cutting before and haven't used SketchUp a lot, so I've decided to start by making a trial cut with the cheapest material - birch plywood. Expectedly, the result was around 20% oversized comparing to my blueprint. The second attempt was much better. I chose to use ABS plastic, which is solid, but soft enough to be cut by a hacksaw or even a sharp knife. Also, it doesn't crack when you drill it as the opposite to plexiglass.

I would like to mention Cotter, an awesome local laser cutting lab located in Copenhagen. Their support team was very helpful when I had questions and the overall experience was really smooth.

I used a hack saw, a utility knife, a thin drill bit and a pair of pliers to cut and fit everything together and then put a lot of hot glue all over the place. It would've been nice to include all of these joint cuts into the blueprint, but again I did not feel like I had enough experience with laser cutting for this. As it appeared to be, some of the holes and cuts on the panel were slightly off, so I had to do some final adjustments by hands. But in the end it was good enough.

Step 3: Wiring Up the Power

When I make projects like this, I always prefer keeping the devices unmodified. That way I could sell PO-24 from the previous briefcase in a perfect condition and replace it with PO-32. Remember I wanted to use a single pair of AA batteries to power the whole setup? You can easily do it by soldering wires directly to the circuit boards, but I did not want that. Instead I've came up with "fake batteries" made of thin wooden sticks, decorative nails, duct tape and (of course) hot glue. It looks funny, but works perfectly.

I've used magnets and metal washers to mount the battery tray lid in place. The handle of the lid is just one of the tiny pieces left after laser cutting the holes for the knobs of the mixer.

Step 4: Wiring Up the Audio

The wiring schema for the audio is almost the same as I used in my previous setup, except for there is now an external speaker with an amplifier board. The audio switch turns the amplifier board on and off in order to extend batteries lifetime when the speaker is not used.

I've got a very small and cheap portable speaker with a nice metal grill from ebay. The amplifier board used a 3.7v battery, but it appeared to be that 3v output of the battery tray was enough for it to work. I've disassembled it and installed its parts separately in the case. There is no back cover on the frame, so the connections aren't protected and can be damaged when the panel is detached. Therefore I've used heat shrink tubes for all switch contacts and secured all amp board connections with hot glue. I guess, there is no way you can make anything look pretty when you use hot glue, but it does the job.

Step 5: Highlighting Labels

Final step - filling engraved labels with an acrylic paint marker and that's pretty much it.

Step 6: Testing

Step 7: Conclusion

Everything worked out quite well and went pretty much according to my original plan. The amount of ground loop noise has slightly increased comparing to my previous setup, but it's only noticeable on high volume level. All in all I'm absolutely happy how this setup turned out and to me it looks much nicer than the previous one I had. If you have any questions, I'd be happy to answer them.