{"id":4926,"date":"2022-08-09T15:39:27","date_gmt":"2022-08-09T20:39:27","guid":{"rendered":"https:\/\/pugix.com\/synth\/?p=4926"},"modified":"2022-08-09T15:39:29","modified_gmt":"2022-08-09T20:39:29","slug":"reverse-landfill-monotropa","status":"publish","type":"post","link":"https:\/\/pugix.com\/synth\/reverse-landfill-monotropa\/","title":{"rendered":"Reverse Landfill Monotropa"},"content":{"rendered":"\n
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I’m on a DIY streak! This is Monotropa v3 from Reverse Landfill<\/a>. It is a 4-band fixed filter designed for distortion and feedback. There’s a knob for the strength of each band, a feedback knob and an output level knob. Three direct-coupled inputs are mixed, with one being attenuated by the feedback pot. The three outputs are AC-coupled, with one having a normal connection to the feedback pot.<\/p>\n\n\n\n

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The module has no voltage control, but… The three DC-coupled inputs allow mixing in of offsets, LFOs, and a second audio source, which can add animation. Offsetting a processed signal sounds a bit like the offset feature on wave folders. Monotropa can self-oscillate, too. And the feedback input and third output can easily patch another module into the feedback loop.<\/p>\n\n\n\n

Construction<\/h3>\n\n\n\n
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I bought a factory kit from Thonk. All the assembly information including BOM, build guide, schematic, and a handy patch guide are downloadable from the link at the top of this post. This is a very easy single PC board, through-hole component project. The parts are all standard. The full kit is handy, because there is a variety of different resistor and capacitor values needed for the four filter bands.<\/p>\n\n\n\n

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Top (back) side on the PCB with all circuit parts soldered<\/figcaption><\/figure>\n\n\n\n
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Bottom (front) side of the PC board, before panel parts are mounted<\/figcaption><\/figure>\n\n\n\n
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Back side again, after panel parts are soldered and ICs inserted<\/figcaption><\/figure>\n\n\n\n
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Pots and jacks<\/figcaption><\/figure>\n\n\n\n
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Bare panel<\/figcaption><\/figure>\n\n\n\n

I added washers under the pots and jacks and used different knobs than the ones in the kit. The pots are Alpha vertical t18 9mm with the split knurled shaft. I happened to have some nice black knobs and used those.<\/p>\n\n\n\n

A Little Demonstration<\/h3>\n\n\n\n

I set up a repeating sound, made with the Athr\u00fa wave folder processing a sine wave and hit with an envelope. This sound goes through the Monotropa. The first part of the recording is the dry, though rich, sound. Then, in succession, I turn up and then down each of the four bands from low to high, with no feedback. After that I start bringing up the feedback and playing around with the band knobs.<\/p>\n\n\n\n