My DIY synthesizer workshop

All my synthesizer modules are completely home-made. I design and etch all my circuit boards, cut and drill my panels etc. The circuits themselves are often designed by somebody else, but I always make prototypes and test their performance, before I invest time in metalwork. Usually the circuits don't completely fulfill my specifications, so I normally make some additions or changes to them.

To test new circuits, I used to make small boards with a standardized connector, that carry the supply voltages, keyboard output voltage and gate. The boards could then simply be inserted in a console, that has sockets for up to seven boards. Now that I have developed the AMORE standard, I usually do the prototypes as AMORE boards. With the AMORE starter kit, I can test all the board's functions.

This is my old test console with (from left to right) the CV quantizer, ASM-1 VCO and saw to tri/sine converter. This has now been replaced by the AMORE exerciser.

How to make circuit boards

I etch my circuit boards in the kitchen. The layouts are done in Corel Draw on my PC. The traces are then printed on transparency film, using my HP Deskjet 720C printer. I use pre-coated boards from Elfa, that have positive UV-sensitive resist. The boards are exposed using an old Philips facial-solarium that I bought at a flea market for SEK 15 ($2).
This yields excellent results. So far, it has happened only once that a trace was broken and had to be repaired. Shorts between traces have never ocurred on the 30+ boards that I have made so far.
All my boards are 100 x 160 mm. If I make smaller circuits I combine several in the computer, and etch them as one board. I saw them apart after drilling, using a jeweller's saw bought at Clas Ohlson.
The holes are drillied using an Emco
Unimat 3 with vertical attachment. I use ordinary HSS drill bits with phenolic paper (Pertinax) boards. They don't wear out bits, like fibreglass boards do. But unfortunately, the Pertinax boards are increasingly hard to find. So now I instead use 1 mm fibreglass boards. Cost is only marginally higher and a 1 mm fibreglass board is as rigid as a 1,6 mm Pertinax one. Of course I had to invest in tungsten carbide drills, but you only need a few sizes.

Etching is easy and reasonably quick, by using this Pyrex dish while heating it on the kitchen stove. Total equipment cost: $3.

Here is the result. Note that routing traces between the IC pins is no problem.

The same board with the parts soldered.

Transistor matching

Crucial for many analog synth circuits is to use pairs of transistors that are matched. To select matched pairs from a box of standard transistors, I developed a board for a transistor matcher, based on a very good method by Ian Fritz.