Duo-Phase Square Wave Mod??

moosapotamus

moosapotamus

Member
@Robert - Since the Bi-Phase originally had a sine/square selector for each of the LFOs, was wondering if you explored doing the same for the Duo-Phase.
https://www.pedalpcb.com/product/duophase/

My cheap o-scope shows a triangle LFO in the Duo-Phase. I poked around a little but could not find a square wave anywhere in the circuit. So, looking for a triangle to square wave converter led me to the single opamp differentiator circuit. Before I consider trying to figure out component values for the diff amp, can anyone smarter than I say if this is a worthwhile path to take? Or, might there be a better approach to adding a tri/sqr switch? Thx!
 
I'll pass on the beh... :rolleyes:
Anyway, I already have a few other mods wired up to the Duo board, so I'm sticking with that.

According to this... https://www.electronics-tutorials.ws/opamp/opamp_7.html ...a single opamp can be configured as a differentiator which appears to be capable of converting a triangle wave to a square wave. I just don't know what component values to use. I mean, I could probably deal with the math, but deciphering the symbols and getting the units right is probably where I would need some help. But, if workable, there is one unused opamp in the Duo that might could at least be used to add a sin/sqr switch to just one section.

Just looking for educated opinions on whether or not this is worth pursuing. And, if so, some advice on setup/component values.
 
Thanks for that, Betty Wont! Dead End FX schemes are so hard to read. But that was a big help! Just a resistor and a cap. The Lola is +/-15V and the Duo is +9V. With the values used in the Lola, I got what looked like a LOG transformation of the triangle in the Duo (shark fins). Decreased the cap from 2u2 down to 47n and got a decent looking square wave. Hope it sounds as good as it looks on my little jtec o-scope. Thanks, again!
 
moosapotamus said:
Thanks for that, Betty Wont! Dead End FX schemes are so hard to read. But that was a big help! Just a resistor and a cap. The Lola is +/-15V and the Duo is +9V. With the values used in the Lola, I got what looked like a LOG transformation of the triangle in the Duo (shark fins). Decreased the cap from 2u2 down to 47n and got a decent looking square wave. Hope it sounds as good as it looks on my little jtec o-scope. Thanks, again!
Click to expand...
hey @moosapotamus
I've been tryin to wrap my head around adding the shape switch to a Phase II build
I checked the Lola and the Duo Phase schematic, but I'm not the best at that
I can see that SHAPE_B adds a 2u2 cap to ground but I can't understand where to add it
Also you mention "a resistor and a cap" Which resistor should be added?
I think this is the right part of the Phase II schematic
1787310981982.png
 
I'm a little under the weather right now, and its been a little while, so I'm struggling with the details, too. For now, hopefully this helps...

Duo-Phase wiring.PNG

These are all the mods I added to my Duo Phase. The tri/sqr mod is in purple. If you do it, I recommend that you also do the filter stages mod. Going through all six stages, the square wave is a bit too aggressive for my taste. 2 stages is perfect. Realize that when you go to the square wave, you are basically turning it from a phaser into a tremolo.

Flashing LED is easy enough. Just do it. Cross feedback is subtle but I like it. Parallel series is only worth doing if you intend to stereo (L/R) inputs on a mixer or go to two different amps.
 
moosapotamus said:
I'm a little under the weather right now, and its been a little while, so I'm struggling with the details, too. For now, hopefully this helps...

View attachment 123028

These are all the mods I added to my Duo Phase. The tri/sqr mod is in purple. If you do it, I recommend that you also do the filter stages mod. Going through all six stages, the square wave is a bit too aggressive for my taste. 2 stages is perfect. Realize that when you go to the square wave, you are basically turning it from a phaser into a tremolo.

Flashing LED is easy enough. Just do it. Cross feedback is subtle but I like it. Parallel series is only worth doing if you intend to stereo (L/R) inputs on a mixer or go to two different amps.
Click to expand...
Amazing, thanks a lot! I'll study this diagram a bit and check what I can adapt on the single Phase II board
I'll surely get back to you 😅
 
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