I’m planning on building a series of MIDI synthesizer modules that will have a pretty simple means of hooking them together, but want something to house them.
I also have a couple of IKEA CD racks kicking around that haven’t been required for a while, and I also don’t want to take up large chunks of floor space for a synth, so I had the idea of using the CD racks standing on their ends as a kind of “vertical” synth rack.
The CD Rack Modular Synth Format
There are a number of synth module physical and electrical standards out there. The most common ones are:
- Eurorack. See the Doepfer A-100 Construction Details page.
- Moog modular. See the Moog Modular Systems page.
A newer “standard” that is becoming popular with some DIY builders is the Kosmo format by “Look Mum No Computer”. You can read all about that here.
I’m not really after modules that will integrated with anything else. All I really want is a common way to power them and then MIDI and audio interconnections. So in true xkcd style, I’ve created my own “CD rack format” with the dimensions based on two starting points:
- The width of my IKEA CD rack which determines the total width of my “modules”.
- The dimensions of easily available aluminium panels.
The width for panel space in my IKEA CD rack is 162 mm. Note that this CD rack had already been trimmed down in a previous life, so it is just under 1m tall.
CD Rack Format Panels
I’ve found a supplier of aluminium panels 250mm wide who can cut pieces for me. This means I can buy 2mm thick 500x250mm panels and have them cut into either of the following:
- 3x 162×250 mm pieces
- 6x 81×250 mm pieces
For less than £15 per original sized panel.
This gives me a basic physical working space for each module of 162 x 250mm. I’ve opted for two sizes of panel:
- Full size: 162x250mm
- Half size: 81x250mm
These fit just perfectly between the sides of the CD rack.
When it comes to actually designing and populating panels, I’m going to leave 20mm spare top and bottom for mounting and drill small holes for M3 screws, which will be inset 10x10mm from the corners as shown below.
In terms of finish, there are lots of options that you can read about online. I’ve seen all of the following so far:
- Enamel paint and lacquer.
- Inkjet printed labels and varnish.
- Vinyl transfers.
- A blank PCB with a silkscreen print.
But I’ve simply used a wire brush obliquely across the front of the panel for a “brushed aluminium” finish. I’ll probably add any labels with a permanent marker! Perhaps not as “synth looking” as black panels, but it is simple for now. I might do something nicer in the future.
The CD Rack Format Case
My CD rack can easily house three 162x250mm panels, but I decided the CD shelves themselves weren’t really thick enough to mount the panels to. Also, I quite liked the idea of space behind the supports for wires and so on, so I’ve cut three additional pieces of wood, each 162mm long, as dividers.
And mounted these in the CD rack in the appropriate places to support 250mm panels.
This gives me three usable 162x250mm spaces and a slightly smaller space at the bottom where I can put a bespoke panel for power, amplifier, speakers, MIDI modules, or whatever else I decide could support the main “rack”.
It also means I can simply drill some small holes through the panels into the wood for the M3 mounting screws.
Case Electronics
I’m keeping things very simple. As all the projects I’m thinking about at present will be microcontroller based, I’m just going to support USB power and let leads drop down from the panels to the bottom of the “rack” where I’ll use some kind of multiway power – either direct 240V 3-pin plugs, or maybe a multi-USB power adaptor.
For MIDI connections, I’m going to support TRS MIDI connections on the panels themselves, allowing simple “patching” of modules. At some point I’ll make some kind of intelligent MIDI distribution, but for now, with only a couple of modules, I’m keeping things simple. I’ve built a simple MIDI 5-pin DIN to MIDI TRS lead to get me started. I had an old “PC joystick to MIDI lead” from many years ago that didn’t work anyway, so I’ve used the leads part and soldered on a 3.5mm Jack. For more details, see my MIDI Connections Cheat Sheet.
Audio output will be by way of stereo 3.5mm jacks on each panel, so I’ll use a simple (cheap) mixer in the bottom of the rack for now with an output to some suitable amplification.
The main goal is not a true modular synthesizer, but more some simple housing for a range of panel-mounted experiments, hence keeping it simple to start with, with pretty much no power or electrical infrastructure in the rack itself.
If things evolve, then I’ll think about a good way to route power, MIDI and audio around the rack.
Closing Thoughts
I’m aiming for cheap, simplicity, practicality and ideally re-use and recycling where appropriate. I think this will serve my purposes very well.
Kevin
Simple DIY Electronic Music Projects 