issue06

EMUSIC-L Digest                                     Volume 34, Issue 06

This issue's topics: Construction of instruments

	filter aside: ob/roland/cem (4 messages)
	
Your EMUSIC-L Digest moderator is Joe McMahon .
You may subscribe to EMUSIC-L by sending mail to listserv@american.edu with 
the line "SUB EMUSIC-L your name" as the text.
 
The EMUSIC-L archive is a service of SunSite (sunsite.unc.edu) at the 
University of North Carolina.
------------------------------------------------------------------------
Date:         Fri, 15 Nov 1991 09:19:25 EST
From:         ronin 
Subject:      filter aside: ob/roland/cem

in preparation for the next phase of experiments, we opened up
a juno 106 and a matrix 6r, to find the signal injection and tap points
for the lopass filters. they were marked on neither, but partly by
inspection, and partly by technical assistance, we have found a couple
of interesting things, and have a question.
first, the juno has epoxy-coated custom ic packs for its signal processing
area. i like that. custom work often indicates some serious design
consideration, and i think this shows in the juno series. those filters
really do sound nice. of course, this makes signal tracing a little
problematic, but we have the info we need. we have been provided with the
critical pinouts on these packs.
the oberheim, on the other hand, uses Curtis ElectroMusic (CEM) 3396 chips
for its main voicing labor. according to the techdood, these things accept
square wave inputs, and perform onboard waveshaping, filtering, and
amplitude control. and there are no bypass points. we can't isolate
the filter. first, this explains a few things, like why the matrix 6
has such a 'flat' sound... i can't believe that CEM devices, while
certainly flexible and price-effective, were ever of superb quality.
is there anyone here who knows of any other commercial synths based on this
company's chips and who can provide some critique of their use? the only
other company i know of off the top of my head is PAiA, and we all
(cough, ahem) know about them.
it also explains that bizzare sawtooth wave that i see on the scope
when i just open the filter and play a straight saw tone. it's not a
sawtooth to begin with... it's the output of a waveshaper.
the other question i have is about the 3396 itself. i didn't actually
get pinouts for the thing, i was simply informed of the impossibility
of my task. does anyone have a data book for CEM? they're long gone, but
i would like to know the actual poop on this thang.

-------------------< Cognitive Dissonance is an Art Form >---------------
Eric Harnden (Ronin)
 or 
The American University Physics Dept.
Washington, D.C

------------------------------

Date:         Sat, 16 Nov 1991 11:11:44 MST
From:         Adam Schabtach 
Subject:      Re: filter aside: ob/roland/cem

> the oberheim, on the other hand, uses Curtis ElectroMusic (CEM) 3396 chips
> for its main voicing labor. according to the techdood, these things accept
> square wave inputs, and perform onboard waveshaping, filtering, and
> amplitude control.

Hmm. Are these still available anywhere? Sounds like they'd be great for
DIY projects.

> is there anyone here who knows of any other commercial synths based on this
> company's chips and who can provide some critique of their use?

Well, the Oberheim Xpander has two different kinds of CEM chips, one
labeled CEM 3372 and one CEM 3374 (I just popped the hood on my
Xpander :-) ). I don't know if either are filter chips, but there
doesn't appear to be anything else on the voice board that could be a
VCF. I think the Xpander's filters are excellent, but there's
obviously a fair amount of circuitry in the filter stage besides the
CEM chip, since the Xpander has 15 different modes. As I recall, the
M-1000 has only one (four-pole lowpass).

Hey, keep up the good work -- this project is really interesting.

--Adam

------------------------------
Date:         Mon, 18 Nov 1991 10:39:30 EST
From:         ronin 
Subject:      cem

adam asked whether Curtis ElectroMusic chips are still available, as
they would be great for DIY projects.
yes, they certainly would. of course, they're out of business, so i'm
afraid that their *actual* (as opposed virtual) utility is somewhat limited.
i believe that another, similar company, Solid State Microtechnology for
Music (SSM), is still in business. the last place i have for them is
in Santa Clara. another thing you might do is call up current manufacturers
who are still doing interesting design things, and ask them what they're
using. oberheim might a good place to start. or, even more, try calling
buchla. they still make modular and hybrid gear, i believe, and probably
at least know of (if not use) sources for specialized synthesis chips.

-------------------< Cognitive Dissonance is an Art Form >---------------
Eric Harnden (Ronin)
 or 
The American University Physics Dept.
Washington, D.C

------------------------------

Date:         Mon, 18 Nov 1991 11:49:41 -0800
From:         Tom Erbe 
Subject:      Re: cem

SSM is no longer in business.  Most of their chips have been licensed to
Analog Devices/Precision Monolithics.  Some of their chips are not being
produced by Analog Devices, most notably, the VCOs.  I know of one
distributer that still has a stock (or did when I ordered last) of SSM
VCOs.  They are Anchor Electronics of Santa Clara, and their number is
(408)727-3693.

Tom Erbe * Technical Director * Center for Contemporary Music * Mills College
  tom@mills.edu * Mills College, Oakland, CA  94613 * (510) 430-2191

------------------------------
End of the EMUSIC-L Digest
******************************