[sdiy] V/Oct accuracy

[Tim Ressel]

Good morning,

I am designing a triangle core VCO and have come to the part of the show 
where I get to pick a voltage reference chip. As I'm sure you're all 
aware the cost goes up as accuracy increases. Initial accuracy I mean, 
as I am trying to avoid a trim. This reference will set the amplitude of 
the wave as well as serve as a voltage for a range switch which needs to 
set exact (?) octaves. So the question is: how much accuracy do I need 
to pay for?

The issue is complicated by the fact that the customer is "west coast" 
and shuns all notions of notes. But as I see it, volt per octave has a 
certain meaning and sets up certain expectations. For example, the 
octave switch should jump the oscillator 1 octave +/- some acceptably 
small error.  In my meanderings I concluded the error should be 6 cents 
or less.

The issue is further complicated by my catching the accuracy bug during 
my stint at what is called Keysight this week. I tend to err on the side 
of minimizing err ;-)  It is an expensive obsession to be sure, and as 
it is my customer that has to pay for it, I need to strike a balance. I 
know there is also drift and resistor tolerances to consider. One battle 
at a time.

Thoughts?

-- 
--Tim Ressel
Circuit Abbey
timr at circuitabbey.com