I Finally Built an ASM-1 Synthesizer.

[gstopp at fibermux.com]

     Yeah Chris you caught me, I didn't actually use a scope or meter to 
     verify the ADSR amplitude, I was guessing! Oh well 7.5 volts is close 
     to 8 volts... Suffice it to say that it is possible to tweak the 
     ADSR's into proper operation given the component values listed in the 
     ASM doc's.
     
     The ADSR output is quite large, potentially 15 volts peak. I did this 
     on purpose since attenuating is easier than amplifying, and besides 15 
     octave VCO sweeps are sometimes fun. Better to have huge signals and 
     level controls. However to keep things standard, especially in 
     "normalled" systems, it's good advice to use the 2K/2K trick so you 
     can patch an ADSR straight into the VCA for example and maintain unity 
     gain.
     
     Another detail - I noticed that the (+) input on the VCA has some 
     crosstalk into the control input, at least on my setup. This means 
     that a large signal sitting on the (+) will bleed itself to the output 
     slightly. I'll be checking this out to see if there's a PCB issue or 
     if it's just my wiring job. The (-) input is fine.
     
     Which leads me to wiring - a trick that may be useful to you builders 
     to keep things organized in that hell we call "wiring up the panel" - 
     I like to use ribbon cable to connect the PCB pads to the panel 
     controls. For example, for the six CV inputs to the VCO, peel off a 
     six-wire wide strip of 24-gauge ribbon cable, connect them to all six 
     PCB pads in a row, and then up to the panel where they split off to 
     the CV pots and jacks. Use common sense to keep inputs away from 
     outputs, to avoid crosstalk.
     
     - Gene
     gstopp at fibermux.com


______________________________ Reply Separator _________________________________
Subject: Re: I Finally Built an ASM-1 Synthesizer.
Author:  Christopher_List at Sonymusic.Com at ccrelayout
Date:    2/4/97 6:15 AM
     
     
     Very sneaky. Good idea, just one thing I wanna point out - the ADSR 
     attack peak will ALWAYS be in the 8 to 14 volt range! It cannot be 
     lower! If you want a 0 - 5v ADSR  - set it up with a voltage divider 
     on the output of (2) 2K resisitors. This will also give you your 1K 
     output impedence.... 0 to 5v ADSRs are standard for a lot of synths 
     and 5v will result in Vin = Vout for the VCA with 100K input 
     resisitors. Another way to achive this would be to have the trimmer go 
     between the output and +v, rather than the output and ground (this 
     would also avoid the "never hits peak" problem)...
     Hmmmm, I bet I can use this trick in my AD + AR circuit and get rid of 
     one of those op-amps - gotta check that schem.....
     
     > D). The "OFFSET" trimpots on the VCF *are* useful - don't leave them 
     off!
     
     I'll second that!
     
     
- CList