Audio VCO with notch for feedback audio tone

[Davor]

Hi all,

as said at thread http://www.geotech1.com/forums/showthread.php?19814 I made a VCO with a notch level response. It may be perfected and that's why I put it here. So far I did not find such audio oscillators, although phase comparators have very similar responses. It comprises a VCO, here a 555 with steered CV which is not too linear, and a one shot with inverted output. Once I sum the outputs I obtain a nice hedgehog-like response which becomes quite nice after some LPF.
One shot can be also steered by it's CV (indicated by V3) to establish some kind of self-stabilising arrangement, like a PLL. I'll play with that later on.

I intend to put it into an off resonance circuit ... and some other places

Here it is, a picture and a LTspice sim:

[ivconic]

...

[Davor]

Yes, most probably it is the same kind of VCO used here, except that mine in this particular circuit has a nice zero at a certain frequency and a certain control voltage. This VCO works in reverse, so for a higher control voltage you have lower frequency and vice versa. The most valuable feature is a notch somewhere in a middle.

I'd say this is a nice one. And it uses only garden variety components obtainable just about everywhere.

[golfnut]

You gotta be kidding right.

Are you Dr Evil... attempting mass brainwash.

I did find myself tapping one foot half way thru.

Mad science right there, fly the flag for all of us davor

S

[Davor]

Glad you noticed

I think it can be optimised a bit, but so far I'm quite happy with the working principle. Perhaps it could be implemented with comparators instead. Both VCO and one shot are no-brainers with comparators too. I'll post some updates soon.