CEM chips

Joachim Verghese jocke at netcontrol.fi
Wed Feb 14 11:25:40 CET 1996


On Wed, 14 Feb 1996, Jeremy Brookes wrote:

> Would I be better going for a CEM 3374 Dual Oscillator over
> two CEM 3340s?

I'd like to point out that the 3374 is *not* two 3340s in one
package. They're quite different.

The 3340 is a complete general purpose VCO with built-in temperature
compensation and waveform converters. With this chip it is easy to
build a stand-alone VCO for almost any application, including modular
synths.

The 3374 is another story. This chip is really designed for
microprocessor controlled applications, where the VCO control
voltages are coming directly off a D/A-converter (via CV de-mux
sample & holds). There's no temperature compensation, only a
temperature sensor output which should be fed to the reference
input of the CV generating D/A-converter. Because of the multiplying
properties of the D/A-converter, any scaling errors caused by
temperature changes will be cancelled out.

Personally, I wouldn't recommend using CEM chips because of the
uncertainty regarding availablitiy. If you still want to use them,
get the data sheets first, and read them carefully. There are lots
of application examples available in the form of analogue synth
service manuals and DIY kit descritpions.

Hope this helps a little.

-joachim



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