DIY Top Octave Dividers

WeAreAs1 at aol.com WeAreAs1 at aol.com
Fri Nov 5 11:26:17 CET 1999


Come to think of it, you might be able to use those 8253 programmable counter 
chips to get the correct division ratios.  These are the chips used in most 
synthesizers that have so-called "DCOs", such as the Roland Junos and the 
Oberheim Matrix 1000 and Matrix 6.  Each 8253 contains three separately 
addressable 8-bit counters, so you would need four IC's to get all twelve 
semitones.  I imagine that the chip would be available in a small 
surface-mount package, so it wouldn't take up much more space than the old 
MK50420 IC (although it might also need a little glue logic to preload the 12 
counter ratios).  It would probably cost about $15 to $25 to build.

If you needed output levels higher than TTL levels, you could add a couple of 
hex level-shifting buffer IC's (such as the 7417 15volt open-collector 
buffer/driver).

Joachim, are you sure that a 9-bit counter is needed to get the exact pitch 
ratios?

Michael Bacich




More information about the Synth-diy mailing list