ASM-1 Parts; MIDI->CV

gstopp at gstopp at
Thu Apr 25 18:17:17 CEST 1996

     Yeah I admit it the parts list is for the circuit board only. Since 
     the panel is a matter of the personal preference of the builder, I 
     left that open. You can try to use psychic energy if you think it will 
     work :)
     *But* I did write up a "suggested panel connections" page for each 
     module, which shows a very generic modular setup. I suppose I should 
     post a list of all the suggested panel parts, since this will be a 
     major fraction of the cost of the final system (depending on the 
     resources of the builder).
     I would consider the absolute minimum number of panel pots to be:
     VCO 1 Fine Tune
     VCO 1 Coarse Tune
     VCO 1 Initial Pulse Width
     VCO 2 Fine Tune
     VCO 2 Coarse Tune
     VCO 2 Initial Pulse Width
     VCF Cutoff Frequency
     VCF Resonance
     ADSR 1 Attack
     ADSR 1 Decay
     ADSR 1 Sustain
     ADSR 1 Release
     ADSR 2 Attack
     ADSR 2 Decay
     ADSR 2 Sustain
     ADSR 2 Release
     VCA 1 Initial Gain
     VCA 2 Initial Gain
     LFO Rate
     Glide (Portamento) Amount
     The Coarse Tune pots on the VCO could be octave rotary switches if 
     desired. You may even be able to get rid of the Fine Tune pots if you 
     use 10-turn or 20-turn panel pots for the Coarse Tune.
     As for any additional controls - there's two primary approaches to 
     modulation routing in modular synthesizers - I'll call them the "Moog 
     approach" and the "Emu approach".
     The Moog approach is to put all the minimum pots on each module, and 
     dealing with modulation depths and signal strengths (really the same 
     thing in a true modular) by the use of attenuators and mixers on 
     seperate panels.
     The Emu approach is to provide all of the minimum pots on each module, 
     and then provide additional pots on each module as input level 
     controls for the audio as well as the CV inputs. The modules become 
     more complex and costly, but more self-contained.
     Whatever you want to do. feel free. The Emu approach will probably 
     cost more and take up more panel space, and lots of pots will go 
     un-used most of the time, but it sure is easy to make patches.
     Regarding the CV and Gate inputs - the VCO and VCF CV inputs are 
     exponential at 1 volt per octave. The Gate input is a positive 
     V-trigger, with the threshold adjustable on a trimpot on each ADSR to 
     be anywhere between ground and +15 volts. There is no pulse trigger 
     input - the ADSR's require only a Gate input (positive voltage as long 
     as a key is held down).
     As for MIDI to CV converters - the builder has to provide this. I 
     personally intend to use CV keyboards, or finish up that PC-based 
     MIDI-CV thing I started (i.e. put it in a box) or maybe even use an 
     MPU-101 (what a great little box *that* is!). I have no experience 
     with the PAIA or Kenton stuff, so maybe others can advise as well.
     - Gene
     gstopp at

______________________________ Reply Separator _________________________________
Subject: ASM-1 Parts; MIDI->CV
Author:  Bob.Schrum at at ccrelayout
Date:    4/25/96 6:57 AM
     The ASM-1 sounds like a great and reasonably affordable project.  One 
     thing intrigues me, though...  Since the parts list contains only 
     trimpots (no panel-mount pots,) I can only guess that the ASM-1 
     features a "brain-wave programming interface!" :-)  How did you 
     accomplish this with such a low parts count?  I see a Nobel Prize for 
     biometaphysics in your future!  ROFL
     Seriously, you can count me in.  What kind of CV and trigger is 
     required?  Can you recommend a MIDI to CV/Trigger interface to use?

More information about the Synth-diy mailing list