[sdiy] LAG circuit de-tuning VCO question

[Oren Leavitt]

On 11/4/2011 6:28 PM, Dave Kendall wrote:
> Hi All.
>
> I have a playing with a simple expo lag circuit consisting of;
>
> 1V/octave input to an op amp wired as unity gain voltage follower, the
> output of which goes through a 1M Linear pot wired as variable resistor,
> then into a second voltage follower with a 1uF cap to GND at its input.
> I notice that without even changing the input CV, setting the pot to max
> de-tunes the output by up to several 100 cents, judging by ear.
>
> The effect is more pronounced the higher the input CV - around 0V to 1V
> input, it's hardly noticeable.
>
> Is this normal, and is there a way to remove the effect? it makes it
> pretty useless for accurate VCO use. One can mitigate the effect a bit
> using smaller resistors/caps, but then the lag time is very short.
>
> Any ideas anyone?
>
> cheers,
> Dave
>

Capacitor leakage - maybe?

- Oren