I built this sort of by accident. Someone was talking about it in one of the synth DIY groups on Facebook and I mentioned that it looked cool and my friend Nick, who I occasionally meet on Bristol street corners to trade circuit boards and programmers, said he had a spare motherboard PCB.
We arranged a trade, including a single voice card PCB and suddenly I had a new project to work on – a 6 voice hybrid polysynth with 12 wavetable oscillators, 6 sub oscillators and all analogue filters and VCAs.
Pusherman had PCBs for the voice cards, so getting another 5 was no problem.
I had a lot of the parts already, so this was a good chance to use up a lot of through hole stuff I had lying around. I ordered in the screen and a few chips and capacitors that I didn’t have.
I built up the motherboard first. All very easy with loads of space. The difficult part was the cleaning! I went though a lot of IPA on this build! The online build guide is very thorough.
Next was the fairly mammoth task of stuffing the voice cards. I did all 6 at once, over the course of a couple of evenings. Again the build guide is very good, so there were no problems. Lots more cleaning though!
I flashed the firmware for the motherboard using my AVRISP MkII programmer and avrdude in the terminal, and loaded the presets onto an SD card. I was very pleased that it all seemed to be working perfectly.
I then flashed the firmware onto all 6 of the ATMega chips for the voice cards.
I put the stack together, making sure the jumpers on the voice cards were set correctly and turned it on. 5 out of 6 voices powered up just fine, but one didn’t, so I pulled it out and reflowed the pin headers, which resolved the problem.
I had a case laser cut by a guy in Poland. I’d seen a few Ambikas in clear cases with all the circuitry showing and I loved the look, so had it cut from clear acrylic.
I’m really happy with how it’s turned out. It looks great and, more importantly, sounds phenomenal.
Here’s a quick demo (apologies for the cheesy progression)…