Hollis Ultra Flanger LFO ticking noise SOLVED!!!

[DimebuGG]

I took my old GEO Ultra Flanger board in my bin(it's there since 2010) and decided to mess with it. My main purpose actually is to get rid of that LFO ticking noise which is the main issue of this circuit. After comparing different LFO's with Boss's choruses/flangers, I take a look at Boss CE-3's oscillator and found out they're somehow similar with the Ultra Flanger EXCEPT there's a capacitor and a resistor which the latter doesn't have. And so I add a 10n cap and a 100K pot wired as variable resistor(Cx and Rx), at minimum resistance the ticking is still present. As I turn the pot (around 56k resistance), Voila! the ticking noise is now gone finally. Cased closed but wait...

After hours and hours of messing with the circuit, I came up with the full schematic as shown(although I haven't tried to add an output buffer). You may ask why the inverters are configured like those in MN3007 A/DA's and EHX EM. The difference is subtle from the stock schematic but I preferred it this way since it sounds "balanced or kinda liquidy" to me as compared to the 3 parallel inverters which sounds mid-dy esp at high depth/sweep. Also I ditch the odd/even switch and replaced it with a mixing pot as shown. After all these are just my preference.

[Mark Hammer]

Yes.  That's the trick Boss used, that is explained here: http://www.moosapotamus.net/files/stompboxology-mo-tremlo.pdf

2-opamp LFOs start with a square wave and smooth/integrate it into a triangle wave.  It is the sudden rise and fall of the initial squarewave that produces the sudden current draw, and the ticking sound.

Boss used the added cap and resistor to make the initial square wave a little more trapezoidal, so the rise and fall aren't as sudden.  Nice to hearthat such a simple change can improve the Utra!