my few ASM questions...

[Stopp,Gene]

>From: Steven Maietta
>Subject: my few ASM questions...
>Date: Friday, April 17, 1998 12:19PM
>
>OK before I start soldering, a few easy questions...
>
>1-In the info I got with the board, using the ASM with a keyboard was
>brought up.  Something with input/output buffers ...I am not really
sure..
>Can anyone fill me in on any tips to make it run smoothly with my KBD/
JKJ
>CV4 MIDI/cv steup?
>
>2-Has anyone done the saw to triangle mod and if so, how did it go?
>
>3-Lastly, does anyone have any of the proper Tempco resistors or
MAT-02's
>left from their experience?  Is the difference really that drastic?
>
>Thanks for any info!!!  Got the SynthDIY ASM archives, recent posts,
info
>packet, c-list's faceplate, and the web-page.. I'm ready!!
>
>~Steve
>

Some answers:

1. My normal advice would be to run the output of the MIDI-CV converter
into the Glide Buffer of the ASM-1, then the output of the Glide Buffer
can be patched to the VCO CV inputs to control pitch. This will give you
adjustable portamento for the pitch when you use MIDI-CV converters such
as the Roland MPU-101. However, the JKJ boxes have portamento build in
(on MIDI CC# whatever), so you can just run the CV from the converter
straight into the VCO's on the ASM-1 and use the Glide Buffer as a lag
processor module in a patch. The Gate from the JKJ can go straight into
the Envelope Generators - set the gate threshold trimpots on the EG's
for around 2.5 volts. There is really no other buffering required, the
EG's have 100K input impedances, the Glide Buffer is the (+) input of a
TL082, and the outputs of everything in the ASM are at 1K or op-amp
output pin (zero ohms, kind of).

2. Only on protoboard - I used the Moog saturating transistor trick,
which was pretty glitchless. Parts count is low, but the schematic is
hidden away. I'll look when I get the chance.

3. No leftover parts here, sorry. Without the MAT-02/tempco combination,
the ASM-1 VCO's work pretty good once you tweak the V/OCT trimpots to
match the room temperature. If the ambient temp changes, you will notice
a slight drift in the V/OCT response, which may not be a bad thing if
you aren't too critical at that point in your project. But if the good
parts are installed, the VCO's will be rock-stable and will track
perfectly all of the time. Indeed, my ASM-1 tuning knobs get touched
less than the knobs on all my other modulars, commercial units of many
brands included. Even when you turn it all off for a few weeks, and then
turn it all back on. Rock stable.

 - Gene