I'm getting rather ambitious and wanting to build a 24-stager based on Francisco's great Ropez project (I have built several basic 4-stagers for friends).  Researching what others have mentioned on this forum about monster phasers, I'm getting the notion that it may be a good idea to include a potentiometer control that will adjust where in the frequency spectrum these notches will go in order for the 24 stages to sound its best.  The Anderton EPFM has such a control.  He calls it offset, but his uses a method for an entirely different oscillator (and inferior sounding to the Ross IMHO because it is a strict triangle and not hypertriangular).  For those of you who are familiar with OTA-based LFO's, is there a way to cut in on the Ross LFO with such a control, or even nudge me in the right direction?  Your assistance would be greatly appreciated.      

You have to be a little careful how you do this.  If you include a trim on the LFO's bias resistors to take the starting point of the sweep higher you loose the 'hyper-triangle' shape.  That may or may not be a bad thing...depends on taste.  If you wish to retain it then you'll need an additional amp that has a variable DC bias.  Probably better to do this anyway as I get the feeling messing with the bias doesn't push the range up much...or something like that (been a while since I breadboarded the circuit).

Cool-Thanks for the hint-That's enough to go on.  I'll try it out and report back!

This is great news! I can't wait to hear about your experience building it and how it sounds.

I suppose you're going to be using the "add extra phase stages" boards and wiring for the task? I've been getting requests on those boards and honestly I haven't had the chance to build one to test it, so mind you it's unverified (it *should* work).

I'll post sound samples when it is up and freaking out the neighbor's dogs.  Parts are on the way from Small Bear.  I am really hoping the LFO sweeps a pleasing area with all of those notches in its stock form.  If not, not big deal.  I do have enough breaboard to mess around with the extra OTA and an oscilloscope.  If I come across something cool, I'll definitely share with all of you.  Thanks again!!     

Cool LP.

I'm thrilled to see the Ross phaser DIY project is finally getting some attention.