Having finally got round to calibrating the oscillators and the MIDI-CV converter properly, I gave alfa4 a little test run with some massively cheesy chord progressions! This is just saw waves from the VCOs going into the quad filter, which is enveloped by the quad VCADSR and modulated by the quad LFO. It’s all going … Read more[Video] – alfa4 Test Run
Having verified the circuit works correctly, I set about putting another 3 of them together for the first envelope module. Then I cut and drilled the panel and labelled it up. I designed this at 38hp, but due to the general inaccuracy of my panel fabrication technique, the gap in the case is 39hp, so … Read morealfa4 VCADSR Prototyping pt.2
I looked long and hard for an ADSR circuit using the CEM3310/AS3310 which had voltage control over all four envelope stages and found only one, with very little in the way of accompanying documentation. It was this schematic by Dr. James J. Clark, which I came across on the Electro-music forum: I decided to base … Read morealfa4 VCADSR Prototyping pt.1
The last of the modules for the 1U row in alfa4 is a quad LFO. They’re just very simple triangle/square LFOs based on a Thomas Henry circuit design. I used a couple of the same boards previously (acquired from John Miscreant via MW) for the dual LFO in my main system and I like them, … Read morealfa4 Quad LFO
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