# FV-1 Detuned Chorus (Pythagorus pcb)



## phi1 (Jan 28, 2020)

This is an adaptation of the Unison Double Tracker PedalPCB patch.  I only used one fv-1 pot input (Depth), which controls the pitch shift up and down together.  I had to adjust the code for pitch down, because in the PedalPCB version, the pitch down knob lowers the pitch twice as much as the pitch up knob, so that was a simple code tweak to get them detuning at the same rate.  The delay time is fixed slightly shorter than the minimum setting on the PedalPCB version.  I tried it without any delay (except the inherent delay needed to do the pitch shifting).  This was sterile and thin sounding, so I kept a short delay which is much more pleasant.  The Mix knob is analog wet/dry mix from the Pythagorus design, and the Volume pot is set to unity by an internal trimmer.  Since only one program is used, I just omitted the toggle switch, and the unused fv-1 pots.

This build is for a friend who I've built a couple other pedals for.  I was showing off my recent Arachnid build with dual eeprom, with 16 patches.  When we got through all 16, he said go back to that chorusy one.  After playing for a minute he said, I want that, just the mix and depth knob.  I tried to explain that I could add more controls and more patches with basically no additional cost / work.  But, he just wanted the simple chorus pedal.

I have to admit, he might be onto something.  I love the simplicity and it really is quite a nice chorus sound (as is the Unison Double Tracker, since it's basically the same thing).  On traditional chorus effects, you have a warble sound because the pitch is bending up and down.  I like how this version gives the depth of the detune, without the warble, since the pitch shift is constant. Also worth noting, whenever people talk about the EQD Rainbow Machine having a beautiful chorus sound, I'd imagine those same people would much prefer this (or the Unison Double Tracker).  The Rainbow Machine is doing something similar when set for chorus (a slight pitch shift), but it's only one direction, and the tracking knob works differently than the delay.  Maybe if anyone has built both the leprechaun and the Unison Double Tracker, they could comment on the comparison.

MISADVENTURE: What's with the white wire routed through the hole for the toggle switch?  Well, I wanted to fit this in a 1590B.  I thought, hey the 2.2" wide Phase II board barely fit in a Small Bear B box.  I thought I could just dremel the sides of the 2.25" wide Pythagorus board until it fit.  This was NOT a good idea (or at least poor execution).  I clipped the trace from FV-1 pin28 to C8 that ran along the side of the board.  So, the white wire remakes that connection.  After dremeling, the board did barely fit, but I decided turning the board sideways was an easy solution in this case. 

Flashing of the chip was done on my PedalPCB FV-1 dev board build.


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## p_wats (Jan 28, 2020)

Great job! I haven't spent enough time figuring out where to start hacking the FV-1 programs yet (beyond SpinCAD), so kudos.


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## Robert (Jan 28, 2020)

Very cool!    I've thought about doing a standalone "Rainbow" style chorus, looks like you beat me to it.


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## daeg (Apr 5, 2020)

phi1 said:


> This is an adaptation of the Unison Double Tracker PedalPCB patch.  I only used one fv-1 pot input (Depth), which controls the pitch shift up and down together.  I had to adjust the code for pitch down, because in the PedalPCB version, the pitch down knob lowers the pitch twice as much as the pitch up knob, so that was a simple code tweak to get them detuning at the same rate.



Can you share the code tweak? I'd like to try it.


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## phi1 (Apr 5, 2020)

So I don’t think I’ll share the full code, since it’s derived from the pedalpcb code which he sells. 

Do you have a pedalpcb fv-1 dev board? Or some other way of reading the code off the eeprom and writing new to the eeprom?  

Anyway, after you have the eeprom and have the code uploaded I could give you the info in a personal message. 

But basically, I did the following:
-move the pot1 function to pot0 (so both shift up & down run on pot0).
-halve the range of the shift down so that it matches the relative pitch differential of the pitch up. 
-set the delay time to default to the minimum pot value (I actually did slightly lower than the original pot minimum).


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