[sdiy] Revision 2 PCBs of my adaptations of the Music Easel Balanced Modulator

Lanterman, Aaron lanterma at ece.gatech.edu
Sat Jul 13 03:17:47 CEST 2013


Most of you are probably familiar with my side project of adapting bits from the Buchla Music Easel to act as stand alone modules.

I finally carved out some time to test the ring mod and crossfader in my 2nd revision of the Balanced Modulator from the Buchla Music Easel. It checked out, and I just got a shipment of them in. I also have PCBs of the earlier adaptations (preamp/env detector, envelope generator, timbre+crossfade, pulser, and Easel LPG) available. If you're interested in building any of these, please e-mail me at abovenyquist at gmail.com (not lanterma at ece.gatech.edu -- the lanterma at ece.gatech.edu is good for most things, and it's how I signed up to SDIY so it's what I'm using here, but I'm trying to consolidate most adaptation-related e-mail to the abovenyquist at gmail.com address). 

I don't think Buchla ever used the same amplitude/ring modulator circuit circuit twice. The circuit in the Easel is differs from the one in the 259, which differs from Buchla 111, which differs from the Buchla 410 (not related to the Buchla 400). The Easel RM is the most far out of the bunch, requiring four vactrols -- two do the main ringmodding, and the other two linearize the first two (I think -- IIRC Grant Richter has the deep know-how on this circuit but I may be remembering incorrectly). Two others vactrols needed for the CV crossfader (fades between unaffected signal and full ring mod signal); you can set it up so that the crossfader works as intended in the Easel, or you can set it up as a totally separate circuit. There's also a 2nd vactrol VCA driven by the same CV as the crossfader, intended for FM control on the Easel, but you can use it for whatever you want here. So the full PCB requires 7 vactrols, which is pricey -- but if you only want some of the subcircuits, you can getaway with less.

- Aaron


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