[sdiy] CV to Expo in a processor

[Tim Ressel]

I figured out if I use a table with 2 entries per semitone the error drops to about 0.055 cents. This sounds good to me. The table will be about 1K bytes, which is a manageable size.

--TimR





----- Original Message -----
From: Neil Johnson <neil.johnson97 at ntlworld.com>
To: Tim Ressel <madhun2001 at yahoo.com>
Cc: Synth-Diy <synth-diy at dropmix.xs4all.nl>
Sent: Friday, July 13, 2012 1:01 PM
Subject: Re: [sdiy] CV to Expo in a processor

Hi Tim,

> I am planning an oscillator using a DCO and having volt per octave CV input. So naturally I am looking at how to take values from the ADC and convert them to increment values that produce the needed frequencies. My first take was to have a table with values for each semitone and interpolate in between values. This leads to a maximum frequency error of 0.217 cents, and the error is always flat. Is this acceptable, or should I increase the size of the table? What is an acceptable error?

I seem to recall a CV DAC tutorial from Paul Schreiber where 6 cents
error was deemed the acceptable worst case error, so I reckon your
table is OK as it is.

Cheers,
Neil
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