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Cem Chips
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bugbrand



Joined: Nov 27, 2005
Posts: 846
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PostPosted: Tue May 02, 2006 1:53 am    Post subject: Cem Chips
Subject description: especially CEM3391 and 3396
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Hi
I was wondering if anyone had any experience with using the uP (I'd thought that meant low-power but now thinking it refers to microprocessor controllable) CEM chips - I've had several 3391s and 3396s for a while now and really want to get them built into modules..

There are a few things I find wierd about them::

1) they both run with a +12v -5v (and also maybe +5v) supply - but seems as though they can also be run at +/- 12v. Why this wierd power requirement?

2) CVs should be ranging from 0 to 4.5v -> the rest of my system generates voltages that'd be outside these ranges so I'm thinking it'd be bad for me to be feeding mod waveforms that have +/-5v ranges (for example)??

3) The 3391 has a 'dual-function' ADSR - requires a 0-5v gate to turn it on, but then it also has 5-8.5v to set the gain of the VCA. Ooo-er that's got me confused.


So far I've not found much info about other than the datasheets (the 3396 one is pretty meaty and a bit confusing to me) - oh, and there's a Digisound DEV91 document that is a 3391 development board - gotta check through that more.. The 3396 was used for things like the Wasp and Matrix6

These chips should be really interesting.!.
3391 contains an ADSR, 4pole filter (with VC cutoff & resonance), and several VCAs
3396 is a dynamic signal processor - waveform modulation converter plus filter and VCA.

Please be more experienced than me!

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tripledot



Joined: Apr 24, 2006
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Location: cornwall

PostPosted: Tue May 02, 2006 5:46 am    Post subject: Reply with quote  Mark this post and the followings unread

If I remember correctly, the CEM3391 was the core of each voice in the SCI Sixtrak and Multitrak synths. Try researching around them, you might find some schematics but that's about all i can help with.

if we're talking about the same chip, then it's basically a complete synth signal path on one chip, albeit a basic one..

try stacking several up at once though, and you might be surprised!
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bugbrand



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PostPosted: Tue May 02, 2006 1:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cheers Tripledot - of course! Stacking up a few would sure be lovely.. I think I've got four or 6 of the chips, so...

..But checking on the Synthtech Cems site it looks like the sixtrack used cem3394 .. in fact that page doesn't list anything using the 3391... Argh. As I say, though, there's the Digisound development board DEV91

If people are interested in the chips, the Synthtech site (above) used to sell some of them at pretty good prices, but they're running low now (various ones turn up on ebay etc though) - there are plenty of different cem chips, some of which seem pretty prized. The 3391 seems pretty unknown, the 3396 semi-famed by the cheetah and matrix6..

They SHOULD be interesting though - lots of functions crammed onto a single chip. (though maybe i'd heard they didn't sound as great as discrete classic designs - but those who know me know that I prefer lots of wierdy devices.. and don't really seek classic synth tones..).

3391 Datasheet
3396 datasheet

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