[sdiy] Re: VCO reset time for BBD-based PM

[JH.]

> The fastest expo VCO I ever did is the one that is the clock VCO used in
> the three phase generator. It goes up to 500kHz. I guess with a faster
> gate you could push this a little further.

I think my storm tide flanger clock VCO goes over 1MHz, but it's ben some
time since I
measured it. Tracking is not overly good, though, and it does need some
hefty HF compensation.
http://home.debitel.net/user/jhaible/jh_storm_tide_1.pdf

> However, I wouldn't rule out PLLs. You could use a "tracking" loop
> filter. (so that settling time does depend on pitch and not on the
> lowest frequency) and use a guiding VCO that runs some octaves above the
> normal range (so you get quicker locking). Then you can use a not so
> precise exponential VCO as the VCO inside the loop (you can then track
> its control voltage to the guiding VCO.) The loop is then not doing the
> entire work of steering the high frequency VCO, but only generating an
> error term which is dependant on the amount of mistracking. This should
> result in smaller settling transients.

Interesting! Do you have a circuit example for this?

JH.