XR2207 and XR2209 VCO chips

[Buck Buchanan]

Hi Malcolm,

First off, as far as I know, the 2207 and 2209 have become somewhat
difficult to find.  At least most of the places I used to see them don't
have them anymore.  The XR2206 is still popular and probably better than
the other two anyway.

Secondly, they have linear frequency sweeps.  So 1V/oct. operation is out
(this is considered the biggest stumbling block).  

That doesn't, however, mean they arent good for LFOs and abstract music
purposes (I've got a couple older modules with these chips in them since my
main focus is weird sounds).  Also cool about the XR2206 is the AM input! 

But for an IC oscillator solution, I would definately suggest the CEM3374.
You can get this from Synthesis Technologies.  It's expensive (~15$) but
worth it considering the time you save - it performs quite well with expo
and linear sweeps I think closer to the order of 100,000:1.  Also a
tempco'd reference voltage out if you go to the trouble of putting it to
use (tho my 3374 oscs are pretty darn stable w/o tempco).

Take it easy,

Buck

At 10:24 AM 1/27/99 -0700, you wrote:
>Ok all,
>
>Can you tell me why the XR2207 or XR2209 VCO chip can not be used easily as
>a basis for a VCO?  I looked at the data specs and it says the have a sweep
>range of 1000:1, minimum.  Wouldn't that just cover the range of human
>hearing (20Hz to 20KHz)?  Lowest frequency 0.01Hz - Highest frequency 1MHz.
>
>Links:
>
>http://www.exar.com/products/xr2207.html
>http://www.exar.com/products/xr2209.html
>
>
>Malcolm
>
>