# Tails mod for Dark Rift Delay



## Stelloh42 (Sep 11, 2020)

Hey all - got a question regarding a schematic I found for a tails mode switch for the Dark Rift PT2399 delay. I'm sure I can build it, and I'm sure that I can connect it to the 3PDT no problem, but I'm wondering just where I should be connecting this to the Dark Rift board? Could just be as easy as figuring out which capacitor is the decoupling cap.

also - I'm aware that having a PT2399 chip in tails mode could mean some line noise - that's a risk I am willing to take.

here's the schematic that was originally intended for a stripboard Mad Professor Deep Blue Delay - I've included both the delay layout and the mod switch layout.

also - if anyone does know of an easier way to achieve this, I'm open to suggestions - but I really would like to build this mod on stripboard and add it to a PT2399-based pedal. I'll probably omit the LED and CLR from the jfet board.

thanks!


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## manfesto (Sep 11, 2020)

Looks very similar to the Tails Bypass board from Fuzzdog, it basically replaces the decoupling capacitor that sits between the input stage and the PT2399, which in the Dark Rift looks to be C5 (in the schematic, you can basically see how if you removed C5, the signal wouldn't ever hit the delay circuit, and it would basically pass straight through from IC1.1 to IC1.2).

EDIT: Looking at the stripboard layouts it's different from FuzzDog's circuit a bit. It looks like they left the 1uF cap on the main board instead of moving it to the daughterboard, which would be a little hard to do with the Dark Rift PCB (you'd either have to raise pin 1 of IC1 and one leg of C5 off of the board and solder the daughterboard's wires to them, or cut the trace on the board with an Xacto knife).

It'd be easier to add the 1uF cap to the daughterboard, then you just need to run two wires from C5's pads. 



			http://pedalparts.co.uk/docs/Tails-Bypass.pdf


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## Stelloh42 (Sep 11, 2020)

Gotcha - move the 1u C5 cap to the daughter board, then run those two wires to C5 pads like a send and return. Thanks so much for your help. Pretty sure I can make this work now!
-Chris


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## Stelloh42 (Oct 6, 2020)

manfesto said:


> Looks very similar to the Tails Bypass board from Fuzzdog, it basically replaces the decoupling capacitor that sits between the input stage and the PT2399, which in the Dark Rift looks to be C5 (in the schematic, you can basically see how if you removed C5, the signal wouldn't ever hit the delay circuit, and it would basically pass straight through from IC1.1 to IC1.2).
> 
> EDIT: Looking at the stripboard layouts it's different from FuzzDog's circuit a bit. It looks like they left the 1uF cap on the main board instead of moving it to the daughterboard, which would be a little hard to do with the Dark Rift PCB (you'd either have to raise pin 1 of IC1 and one leg of C5 off of the board and solder the daughterboard's wires to them, or cut the trace on the board with an Xacto knife).
> 
> ...





manfesto said:


> Looks very similar to the Tails Bypass board from Fuzzdog, it basically replaces the decoupling capacitor that sits between the input stage and the PT2399, which in the Dark Rift looks to be C5 (in the schematic, you can basically see how if you removed C5, the signal wouldn't ever hit the delay circuit, and it would basically pass straight through from IC1.1 to IC1.2).
> 
> EDIT: Looking at the stripboard layouts it's different from FuzzDog's circuit a bit. It looks like they left the 1uF cap on the main board instead of moving it to the daughterboard, which would be a little hard to do with the Dark Rift PCB (you'd either have to raise pin 1 of IC1 and one leg of C5 off of the board and solder the daughterboard's wires to them, or cut the trace on the board with an Xacto knife).
> 
> ...


Hey again - I've got one more question regarding the placement of the 1uF cap if I move it to the daughter board for the tails mod. Should the cap be the first thing the signal hit from the 'send' wire from the Dark Rift PCB? Or the last, just before the return BACK to the PCB? I was planning on using a film cap instead of an electrolytic so polarity won't be an issue.

thanks again for the help on this!

-Chris


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## Stelloh42 (Oct 6, 2020)

Stelloh42 said:


> Hey again - I've got one more question regarding the placement of the 1uF cap if I move it to the daughter board for the tails mod. Should the cap be the first thing the signal hit from the 'send' wire from the Dark Rift PCB? Or the last, just before the return BACK to the PCB? I was planning on using a film cap instead of an electrolytic so polarity won't be an issue.
> 
> thanks again for the help on this!
> 
> -Chris


Actually - I looked over Fuzzdog's schematic for his mod board, and from the circuit diagram, it looks like you are supposed to have the capacitor moved to the daughter board so that it is the last thing the signal hits before returning to the main PCB. So I think I may have solved this one myself!


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