I Finally Built an ASM-1 Synthesizer.

[Christopher_List at Sonymusic.Com]

     Hi DIY and Gene -

     > If you look at the schematic you will see that I cheated and did
     > not use a comparator to detect the peak-reached state, I just shove
     the ADSR
     > output back into the bottom CMOS NOR gate with a trimpot.
     > This means that the logic threshold of the chip is used as the
     comparator
     > (sneaky, huh?).

     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