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I’m considering an aluminium housing for the final version of alfa4, but for now, the prototype modules need a better home. I was using my two DIY 3U cases, but I wanted one unit, so I cannibalised them. I designed a 7U box on MakerCase and sent it off to Laser-web to be cut. It … Read morealfa4 Prototype Case

Still on a 1U tip, I wanted to add a noise source for mixing in with the oscillators, so I raided my spares box and looked for a simple schematic. I found this René Schmitz design which someone had already done a layout for, so made my life very easy. I built the circuit up … Read morealfa4 Noise

I was always going to have a 1U row as part of alfa4, I just wasn’t sure what to put there (aside from the nameplate!) It became immediately apparent during my initial tests of the first couple of modules that I was going to need some multiples. So I made some. That’s it really! Not … Read morealfa4 Multiples

This has been a huge build, but it’s finally done! I made up the other three filter circuits, having confirmed that the first one worked. I cut some slots in the boards to allow the wires to pass through the layers. I made up an acrylic panel roughly to my photoshop design and popped all … Read morealfa4 VCF Prototyping pt.2

I looked at a few different options for polyphonic MIDI control of the alfa4 system. I knew it had to be digital (it will be the only part of alfa4 that is!), so I explored various chips, considered writing something for Arduino, but realised that I have exactly what I needed in my main system … Read morealfa4 Polyphonic Midi-CV

I’ve picked up a few AS3320s along with the rest of the Alfa chips, so I went looking for a nice low pass filter design using that chip to get me started. I found the AMS AM8320 “Prophet” filter. It looked pretty much what I was looking for and the schematic’s available (via the link … Read morealfa4 VCF Prototyping pt.1

Finally finished the prototype for the quad VCO! This has been the biggest, hardest build I’ve done so far. Building from raw materials always takes longer and this is a pretty big module. First job was building the remaining two oscillators. I also added some 3 pin headers to my power bus. Then came the … Read morealfa4 VCO Prototyping pt.3

I’ve made a temporary panel for the first iteration of the quad VCO module. I printed off my design and taped it to a piece of 2mm acrylic cut to 28hp, then drilled pilot holes. I widened out the holes to the correct size with a stepped bit. Not too hard to get the position … Read morealfa4 VCO Prototyping pt.2

I wanted to prototype all of the circuits for the polysynth, so made a start with the VCO. I also wanted to make sure that the panel layout I’ve designed would actually fit. I’ve picked up all the chips I need from Alfa – 4 x AS3340, 4 x AS3320, 8 x AS3310 and 4 … Read morealfa4 VCO Prototyping pt.1