Arp Quartet cheap?

terry michaels 104065.2340 at
Fri Nov 5 13:00:02 CET 1999

Message text written by Harry Bissell
>Its no secret whats inside the top octave generator... its just digital
that have the 12th root of 2 relationship to each other. <

This is actually more complicated than that. The ratio listed above cannot
be exactly duplicated by integer dividers, which is what you get with flip
flops and gates.  The Mostek device starts with an approximately 2 MHz
counter, and divides that by 12 different integer amounts to approximate
one octave of equally tempered notes, with a tolerable amount of error.  If
you were to duplicate this function with a gate array, etc., many other
initial clock frequencies and divider ratios are possible, you will
typically tradeoff the total number of gates and flipflops against equal
temperment error, a higher initial clock frequency and larger divider
ratios can more closely approximate the 12th root of 2 relationship.

Terry Michaels

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