nLog

I am the Wire. Feeed Meee.

My latest project has been the construction of a Theremin. I chose the Paia kit as a basis, because of its reputation for producing a controllable instrument with a great tone. Controllable is important for a theremin, because of the deserved reputation as the hardest instument of all to master.

Sadly, I got caught up in building this thing, and didn't take the time to obsessively document the process of construction. There are a another couple of photos on my Flickr page.

However, before I forget, here are some construction notes to assist prospective therenaughts:

- I chose the Paia kit over the locally available Jaycar Kit for the aforementioned control and tone. The Jaycar kit produces great sci fi sound effects, but has reputation as being difficult to produce a tune from. There was a site with mods to help the Jaycar kit, but I could not find it, and there is an established community of experementers who have written up mods for the Paia. I ordered the base kit, and the partial case kit, less the US power adapter.

- Paia are the sort of company that publish their full instructions and schematics online so you know what you are in for before you buy. Theoretically, a skilled constructor could produce their own kit from these instructions, as there is even an image of the circuit board. But Paia are still happy to sell you just the board if this is the route that you want to go down.

- I elected to save on shipping by getting the kit without the lectern case. I now think that this was not such a good idea. Modifying the box by making cutouts for the controls took a long long time. I spent as much time sanding as I did soldering. Not to mention the mission to find a suitable box, and the multiple trips to the hardware store to get the tools to do this task and acheiving a high quality finish. The cost of the box, less labour was still less than the Paia lectern. But the cost of scratch constructing a case, especially if you don't have the tools or the wood could be 2-3 times the cost of the Paia lectern incl shipping.

- Building a theremin into a suitable 'found' case, such as an old instrument case, a shop dummy or a tin robot is part of the ethic of theremin building. But old wooden boxes now fetch a crazy price at antique/junk shops so I had to go with a faux rustic bread box made of offcuts from the production of faux rustic furniture. It still looks fantastic, and despite being a knock off, it is much preferred to freshly logged non-plantation native woods.

- On that note, I used the drill a round hole in each corner of where the cutout should be and cut in between the holes with a $10 coping saw. Big mistake. A cheap coping saw too flexible, so you will end up with a large amount of wood to be removed cross grain. Hence the extreme amount of sanding required. I almost dropped dead when I noticed that every department store has electric jigsaws for NZ$14.95 which would have done the job cleanly in a few minutes with minimal sanding. In the end, I used the saw on my leatherman to make the final cuts and trim a lot of the excess away. A stanley keyhole saw would do a similar job, but still costs more than a cheap jigsaw.

- Get a good soldering iron. I use this iron from Goot/Jaycar. It is a higher wattage than most irons recommended for such projects (eg 25-30W), but is temperature controlled like a much more expensive soldering station. This means, that the tip stays at a steady 320 deg C (prettly low for a soldering iron), which is great for the delecate components but the iron has 'horsepower' in reserve so can easily melt solder onto the metal lugs of the controls.

- The same goes for solder suckers, and wire strippers. I purchased a fantastic Goot solder sucker that made cleaning up after soldering accidents a breeze. And the cheap 'automatic' wire stripper that I have (Similar to this) saved a lot of time when it came to wiring up the panel.

- Instead of soldering the delicate ICs to the board, I soldered on IC sockets. This is the priciest and most complex kitset I have built, and I didn't want to risk frying the ICs. Now I have built the kit and it works fine, I may solder them directly, but the kit sounds good so there is no pressing need. The downside of IC sockets is that the ICs can work their way free if the instrument is transported around a lot, so soldering is best for a gigging machine.

- Solder on, with Codral, solder on....

- Some sort of plastic tv tuning screwdriver, or even a plastic knife cut down a bit is essential when it comes to tuning the oscillator coils at the end. Metal screwdrivers mke it very hard to get the coils adjusted to null point. Read the Construction FAQ on the Paia site, as it contains several helpful tips about tuning.

- A large case has raised the prospect of installing an internal speaker to make the theremin self contained. Watch this space....

Posted by nic at 09.07.06 11:28