[sdiy] How to start tuning a specific VCO driven by a specific keyboard's CV...

[Andre Majorel]

On 2012-01-27 14:20 -0500, Jean-Pierre Desrochers wrote:

> Suppose we have a 61 keys synth keyboard that  
> produces 0-5.00vdc output (6 octaves span)

*5* octaves span by my count.

> If I put the VCO's RANGE selector at 8' position,
> put the FREQUENCY pot at mid position (0 semitones)
> and press the very first left C key of the keyboard (0.00vdc)
> what frequency should I expect from the VCO as
> a start for tweaking it's inner trimmers ?

The notion of footage comes from pipe organs. It is the
approximate length of the longest pipe in a stop. At 340 m/s
and 1 foot = .3048 m, an 8-foot pipe would ring at about 69.7 Hz.

For electronic instruments, 8' means 440 Hz on the middle A. On
a 61-key keyboard, the low C would be 440 / 2 ** (2 + 9/12) =
65.41 Hz.

-- 
André Majorel http://www.teaser.fr/~amajorel/