{"id":719,"date":"2012-05-04T10:21:31","date_gmt":"2012-05-04T15:21:31","guid":{"rendered":"http:\/\/pugix.com\/synth\/?p=719"},"modified":"2017-07-28T09:54:45","modified_gmt":"2017-07-28T14:54:45","slug":"modular-tetrazzi","status":"publish","type":"post","link":"https:\/\/pugix.com\/synth\/modular-tetrazzi\/","title":{"rendered":"Modular Tetrazzi"},"content":{"rendered":"

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After I received my Ciat-Lonbarde Tetrazzi Organ<\/a>, I spent a lot of time delving into its design.\u00a0 I wanted to understand it as well as possible in order to be able to play it well manually.\u00a0 By design, Ciat-Lonbarde instruments are intended for play, as in fun, and their operation is to be joyfully discovered, rather than coldly reasoned out.\u00a0 I like to play, but my brain also likes to figure out.\u00a0 I used the paper circuit diagram, together with the schematic diagrams provided by Peter Blasser, and conducted my own experiments.\u00a0 These then were my starting points.<\/p>\n

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Shown above is Peter B’s schematic for one of the four Tetrazzi oscillators.\u00a0 It is an ingenious design for a voltage-controlled sawtooth\/ramp oscillator, where the up and down rates are separately voltage controlled.\u00a0 Not only are the rates under VC, each VCO has two modulation inputs, one for up (UPMOD) and one for down (DONMOD), that are hard-wired internally to come from the other VCOS.\u00a0 The internal patch looks like this:<\/p>\n

UPMOD cross connections:\u00a0 [1 -> 4; 4 -> 3; 3 -> 2; 2 -> 1]
\nDONMOD cross connections: [4 -> 1; 4 -> 2; 2 -> 3; 2 -> 4]<\/p><\/blockquote>\n

The depth<\/em> of modulation for UPMOD and DONMOD are under voltage control, all four being simultaneously controlled.\u00a0 The different topologies for these two internal patches is the reason behind the different sound experienced for UPMOD vs DONMOD.\u00a0\u00a0 Did I just reveal a secret?\u00a0 No, it is discoverable to anyone who takes the time to understand the paper tetrazzi.\u00a0 If you click this image, save the GIF, and print it, you will have the paper Tetrazzi.<\/p>\n

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Functional Structure<\/strong><\/p>\n

The Tetrazzi consists of the following circuit elements:<\/p>\n