DIY Modular Synth: Case

IMG_7231I’m very pleased to announce that a PCB or a complete DIY kit of the power distribution system I designed for this case is now available for purchase from


A while back I built a small, cheap modular case to house the first handful of modules that I’d built. This did the job nicely while I was finding my feet and working out if I could progress with building my own modular synth, but I very quickly outgrew it.

So, soon after putting my cheap little plastic-box-case into use, I found myself starting to plan what my real case should be like. I soon got a list of key features together:

  • An attractive, solid hardwood frame, strong enough to handle frequent handling and movement
  • “Proper” mounting rails
  • Space for at least 2 rows of 12 units each
  • A power supply and distribution system sufficient to supply a full case of modules
  • Power to come direct from mains; no wall-wart adaptors!
  • Cost-effective!

Developing the plan

I spent a few evenings Googling for ways to tackle this list, looking at products, materials, prices and reading up on the skills that I’d need (I’m no carpenter, after all). After letting it all percolate and slosh around in the subconscious for a month or so, I found that I had come up with a set of solutions.

Hardwood frame – this was looking very tricky and expensive until I found this website with their range of hardwood window boards. Even with the delivery charge, this was by far the cheapest method of obtaining the wood that I wanted (I’d opted for Ash at this point) without having to do a load of cutting to get to the dimensions that I needed. Buying board at the right thickness in a depth that I could just roll with would mean that I’d only have to make and square up 8 cuts to build my frame.

Rails – shopping around for rails took ages. I looked at so many different types of aluminium section that I suspect I’m now a world expert on the subject. And the prices of some of the options – it was looking very much like there’d be no way I could put a case together on a modest budget. I even briefly considered just using plain L-section and drilling/tapping my own mount holes in, just to keep the cost down.

But then I found MakerBeam, a 10mm x 10mm aluminium slotted profile system that was a) ideal for mounting my modules and b) very cost-effective (a 600mm beam costs just over £5). The same system would also give me a means of mounting internal hardware such as my power supply and power distribution boards.

Space – I took the 600mm beam length as being my frame width, which would translate into 2 rows of 13 units each, leaving just a small 10mm-ish gap to mask at each end of the rows, and there’d be no cutting to do at all. I opted for MakerBeam brackets with which to install the beams into the hardwood frame.

Power – after a lot of research, I designed and built a power supply and power buss for the case, the details of which are covered in the linked posts.

Cost-effective – deciding whether this build turned out to be cost-effective is tricky. I ended up spending more than I intended, partly because I had to buy tools for some aspects of the job (of which there is more later) and partly because I up-spec’ed some of the materials as I went along. For example, I’d originally intended to frame the case with 16mm birch ply, which would have been a lot cheaper than the 20mm hardwood that I eventually settled on. However, the case wouldn’t have turned out anywhere near as aesthetically pleasing had I done this, and there would have been a lot more woodworking involved as I wouldn’t have been able to source ply pre-cut to one of my critical dimensions with four faces already squared. It’s a bit difficult to weigh up how the material cost offsets the time-and-effort cost. In total, excluding tools, this case cost around £160 to build – including power supply – which in comparison with a ready-made solution feels like good enough value!

The most important thing, as I went through the process of getting the plan for the case together, was that I kept lists, links and an increasingly detailed solid model up-to-date at every stage. By the end of this “discovery” process, I had a complete solid model of the case, with all  of the fine positioning and construction details worked out before I’d even spent anything on materials.

An early version of the model, somewhat over-engineered compared with the finished design.

I used the free version of SketchUp to build my model; lots of components (such as handles, feet and even MakerBeam profiles) have already been built by other people so it was pretty easy to put together an accurate model very quickly.

Techniques and tools

Having pretty much no skill in woodworking, I opted very early on for a very simple (but still very strong) approach for building the joints for my frame. I’d make probably the easiest woodworking joint that fulfilled the criteria – an end-to-face dowelled joint.


The main aesthetic advantage with this joint is that, being glued, there are no visible screws on the outside, leaving a nice, clean look to the frame.

To achieve this, I needed to be able to make a straight, accurate cut in my timber, flatten and square the cut ends and then accurately position the dowels. This led to the acquisition of some new tools and some new skills!

Back saw – for cutting, I chose a back or tenon saw. This short saw has a fine cut and the blade is held rigid and straight by a metal spine. I found that the way to achieve a good, clean, straight cut was to set up a jig out of scrap timber to guide the blade and then cut slowly and carefully. It took a long time, but I’m happy to say that every cut turned out well.


Block plane – as the cut ends of my timber consisted entirely of end-grain, this short, shallow-angle plane was ideal for reducing the cut length to my required dimensions and squaring up at the same time. The key thing here, discovered by trial and error by working on some scrap pieces, was to get a really sharp edge to the plane blade (or “iron”). New from the shop they’re really not that sharp, but I found a great technique for sharpening with sandpaper that worked a treat and got a real razor-sharp edge. Again, slow and steady was the way to go. I think I probably spent as much time on cutting and squaring as I did on the rest of the build put together!


Dowel jig – I tried to work out any number of ways of setting out dowels accurately before just capitulating and buying a proper, self-centring dowel jig. It worked brilliantly, too, so that was money well spent. I found this to be the most nerve-wracking part of the entire build, as I’d invested hours in cutting, planing and sanding up to this point, but a mistake here could effectively wreck the work I’d put in so far!


Band clamp – for clamping the finished frame while the glued joints dried I bought a very long band clamp. Exactly the right tool for the job.


To this list of tools I added a bunch of stuff that I already own – mallet, Stanley knife, try square, straight edge, drill, various woodworking drill-bits, screwdrivers, clamps, etc. It took a long time, but I got there in the end!


With the woodworking done, assembly was actually pretty straightforward. I added 15mm square battens to the back of the case so that the back panel (a piece of 6mm plywood) could be attached with screws. The module and PSU MakerBeams just screwed in, as did the external fixings like the handle and rubber feet. I made sure to create pilot holes for all of the screws as hardwoods can split quite easily if over-stressed, but the whole thing went without incident. All of the assembly happened over the space of a couple of days.

Once I’d done a complete assembly, the next step was to take it all to pieces again so that I could apply some shine.


Having stripped the case back down to just a wooden box, I worked round it with progressively finer grades of sandpaper. This took a couple of evenings but was very pleasant and therapeutic. I started using phrases like “releasing the grain”, which wound my family up beautifully.

After sanding, I gave the whole thing a wipe down with some white spirit and then applied a coat of clear varnish. After letting this dry for 24 hours, I gave it a final light sanding and then spent a couple of days just building up layers of varnish (I went to 5 coats in all). I allowed this last coat to dry thoroughly before re-assembling the complete case.

Finally, I gave the finished case a firm polishing with just a branded spray polish, nothing special. I think it’s the time I spent, the number of very thin coats of varnish and the care and time taken that gave the result that I ended up with – which, I have to say, I am very pleased with and proud of. The joints aren’t perfect (naturally, I already know there are things that I would improve next time) but they’re perfectly good enough. And, most importantly, it’s mine, and it’s unique.


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