[sdiy] Linear/Log FM (was "Living VCOs" PCB in 2009 ?)

[Ian Fritz]

At 08:53 AM 12/10/2008, Simon Brouwer wrote:

>I have been planning to include a single "linear detune" control on the
>2-VCO synth I'm building. It should be an easy modification on the ASM-2
>VCO: a pot connected between ground and -15V, two resistors to divide the
>voltage down, a 10M resistor to inject current into the virtual ground of
>the integrator, and a trimpot to null the offset voltage of the integrator
>opamp.

Sounds good.  But will that VCO have enough starting stability and 
accuracy?  Remember, 1 Hz out of 2 kHz is 0.05%.  I'm not saying it can't 
be done, but I think you'll have to be careful choosing parts, keeping the 
circuit away from any kind of air currents, etc.

Ian