TriVibe - couple of questions

[ChrisKelly]

Bit of a noob question here, but what is the purpose of the 22R resistor at the 9V power source?

Also, with the 'depth' pot - this looks to be altering the non inverting voltage on the final opamp before the LFO output. I'd like to use the TriVibe circuit for an LFO on another project, and was looking for a way of being able to make use of the square and triangle wave outputs too, but with depth control. If i added an extra opamp stage and sent the square/triangle outputs to it, could I simply add a depth pot in the same way? E.g wiper to non inverting pin, one of the other lugs to the triangle output and the other to Vref?

[ChrisKelly]

Sorry - forgot the link to the schematic

http://www.runoffgroove.com/tri-vibe.html

[rankot]

Bit of a noob question here, but what is the purpose of the 22R resistor at the 9V power source?

To form a low pass filter together with 470u, so most of the noise from power supply is rejected.

[ChrisKelly]

Thanks for the answer 

[rankot]

Even 8R2 should be sufficient there.

[blackieNYC]

The trivibe article accompanying the schematic seems to describe that third op amp stage as some additional sine wave shaping so no, you could not get a square wave using the depth control as is. 
I don't know what other effect you want to drive with the same LFO, but see other LFO circuits that give you access to the square wave and try to implement that. You'll tap in a little "earlier" in the LFO circuit.  Jenny Greenteeth maybe? Or the tremulous lune? The trivibe itself is pitch modulation, which might sound unpleasant with a square wave LFO.

[ChrisKelly]

Thanks for the suggestions. I can tap into the square wave at pin 1 of U3, and the triangle at pin 7. Both sound OK but no depth control - like you said, its after the sine-wave shaper where you get depth control