[sdiy] Looking for low parts count HF-VCO

[Scott Gravenhorst]

"Daniel Araya" <daniel.araya at sr.se> wrote:
>Hi, 
>
>I need a simple VCO with a range of about 500kHz to 1,5Mhz, I need it
>vary the samplerate of an ISD sampling/playback IC. 
>I vaguely remember somebody using a 4046 and have also read about using
>555's for HF VCO. 
>The stability of the VCO isn't that important, it's a pretty lo-fi
>sound in the ISD IC's anyway.

CD4046   can go to 1.3 MHz
74HC4046 can go to 17 MHz

It is a voltage controlled oscillator, but I didn't find it very linear, but that
might not matter for your application.  Not many external parts are required.  Power
specifications are very different for these to ICs, so read the datasheets.

If you need better linearity, try http://www.uni-bonn.de/~uzs159/vco4069.html which
is still one IC (4069UB) plus a couple of transistors.  This one has expo freq
control, I've made a linear pitch CV input for it.

I think that the low-parts count winner is probably going to be the 4046.  The
datasheet should have a test circuit you can modify to be just a VCO instead of a
full blown PLL.

-- ScottG

---------------------------------------------------------
-- Scott Gravenhorst
-- Xilinx Spartan-3E Based Music Synthesizers
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