F-V converter and Ring Mod. stuff

Christopher List Christopher_List at sonymusic.com
Wed Feb 14 13:48:26 CET 1996


>   noise a little". I then took Don Till's advice and tried the 
  >   exponential-discharge capacitor into a sample & hold idea. It looks 
  >   good on the scope, but I had trouble trying to get it to convert at 1 
 >    volt per octave using scope period measurement and a DVM. I probably 
 >    would have had better luck listening to a VCO while tweaking the 
 >    converter gain. Heck, as is it may be better than that goofy Korg 
 >    MS-20 pitch follower...

Have you (or anybody) looked into the AD650 V-F / F-V converter? - They're 
pricey, like $18 a pop, but from what I could tell from the data sheet (not too 
much) it should have very good linearity on the output voltage for frequencies 
up to a few kHz. It does require input pulses - and, as you say, the input 
conditioning is the tough part. - Probably not worth the money, but it does 
make the f-v put really easy...

BTW, Gene, your warning about 0 denominator division circuits didn't go 
unheeded - that's the last thing I need is for my little AD633 multiplier / 
divider to cause a brownout over half of Greenwich Village. :) I did get some 
of these (AD633's) and they work great as ring. mods. perfectly, from what I 
can tell, so easy - $6, not bad. I think the ASCII schem at music machines for 
this guy might be flawed (I used my own layout based on the data sheets) - but 
my at home i-net provider seems to have gone belly up so I have no web access 
to check it. For +5v peak input signals, you can't just use the output 
straight, because the chip has a 10v denominator so you'll get 2.5v peak 
output. You need to use a 2 * 1K ohm voltage divider on the output to feed the 
signal back into the "Z" input. I also used voltage dividers between my offset 
trimmers and the chip to get very fine adjustment. 

-CL
(No TV)



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