# Percolator Mod…



## Coda (Jul 19, 2021)

I am thinking of adding a toggle (SPDT- on/off/on) to a Harmonic Percolator Injust built, in order to choose between either of the diodes, or no diodes. I could use a second opinion. As I see it (which is almost always the wrong way), I would connect the diode to one leg (? I can’t remember what they are called) of the switch, and then wire the middle lug (I remembered!) to to be, where the other end (negative) of the diode would go, correct?


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## fig (Jul 19, 2021)

Think of it as in/out, with the center lug being being IN, and the OUT being one of 2 diode legs soldered to lug 1 or 3.


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## Coda (Jul 19, 2021)

fig said:


> Think of it as in/out, with the center lug being being IN, and the OUT being one of 2 diode legs soldered to lug 1 or 3.


So I run a wire from the positive side of the diode on the pcb to the center lug. Then I connect the positive end of the diode to the outer lug, and the other end back to the negative diode of the pcb. Right?
Edit: I posted the above before I let the photo you attach load. Would it matter that the diodes in question are not together in the circuit?


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## Coda (Jul 19, 2021)

Since I want to choose between one of the two diodes, I would need a different switch, judging by that, correct?


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## Feral Feline (Jul 19, 2021)

If I understand correctly what you're saying, then yes, it would matter. You'll have asymmetrical clipping if they're not together. 

So you mean... you've got a total of 2 single diodes and you have one on Lug 1, and the other on Lug 3? It'll sound the same if they're the same type of diode and if it's the on-off-on switch. 











You could rig up a switch to make it symmetrical, off, asymmetrical...


I like to use DPDT on-off-on and put sockets in the middle with LEDs and then silicon or Ge, symmetrical & asymmetrical on the outer lugs. The higher forward voltage of the LEDs is ignored in either "ON" position of the switch; in the OFF position you've got LEDs or manually remove the LEDs and you've got the no-clipping option.

If the PCB has pads for a set of diodes, you can use a SPDT on-off-on (again, I'd socket the PCB's clipping diodes and stuff the sockets with LEDs (or not)...






AMZ's SPDT


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## Coda (Jul 19, 2021)

Feral Feline said:


> If I understand correctly what you're saying, then yes, it would matter. You'll have asymmetrical clipping if they're not together.
> 
> So you mean... you've got a total of 2 single diodes and you have one on Lug 1, and the other on Lug 3? It'll sound the same if they're the same type of diode and if it's the on-off-on switch.
> 
> ...


Here is the schematic.

I socketed the two Ge diodes, and experimented with them both in, both out, one I and one out, and vice versa. I’m not a fan of the both in sound. I like it with no diodes, and I like the sound with one diodes (d2 and d3) I want to be able to switch between no diodes, d2, or d3.


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## Feral Feline (Jul 19, 2021)

Coda said:


> Here is the schematic.
> 
> I socketed the two Ge diodes, and experimented with them both in, both out, one I and one out, and vice versa. I’m not a fan of the both in sound. I like it with no diodes, and I like the sound with one diodes (d2 and d3) I want to be able to switch between no diodes, d2, or d3.


There's no D3 on the schematic.

The D100 diode protects the circuit and should not be removed.

So you like the sound of D2 and its associated resistor (R5)?
If you want no diodes and just D2, that's no problemo.

EDIT: You could have "asymmetrical — none — asymmetrical" using a SPDT on-off-on, since you're not a fan of symmetrical clipping. 

Three different sounds. Try a single silicon or LED or Schottky in one side, the stock D2/R5 on the other side and nuttin in da middle.


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## Coda (Jul 19, 2021)

Feral Feline said:


> There's no D3 on the schematic.
> 
> The D100 diode protects the circuit and should not be removed.
> 
> ...


I meant D1 and 2. What you described is what I would like to do: D1/no diode/D2


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## Dan0h (Jul 19, 2021)

This is a great thread, I might have to try this.


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## Feral Feline (Jul 19, 2021)

Coda said:


> I meant D1 and 2. What you described is what I would like to do: D1/no diode/D2


Also give the 3-diode anti-parallel asymmetric a try (#4 in the "Basic Diode Clipping Variations" graphic, or any of the 3 (A/B/C) in the "Asymmetrical Clipping" graphic in post #5. 

I quite like asymmetrical clipping as well — LED anti-parallel with a Schottky ("B" in the "Asymmetrical Clipping" chart) is a fave.


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## fig (Jul 19, 2021)

try everything, but try an orange LED


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## Coda (Jul 19, 2021)

Feral Feline said:


> Also give the 3-diode anti-parallel asymmetric a try (#4 in the "Basic Diode Clipping Variations" graphic, or any of the 3 (A/B/C) in the "Asymmetrical Clipping" graphic in post #5.
> 
> I quite like asymmetrical clipping as well — LED anti-parallel with a Schottky ("B" in the "Asymmetrical Clipping" chart) is a fave.


Things brings us back to my original question: how to wire the switch.


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## Feral Feline (Jul 19, 2021)

Just like Fig showed you, but remove one diode from each side — singles instead of pairs.

EDIT: Actually, you could simplify it further by wiring the two diodes' negative side together.






Where "SW1" is the signal side coming from the PCB and "SW2" goes to ground (again, ignore the double diodes, just pop it with a single on each side). One wire from the board, 1 wire back to ground.


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## Coda (Jul 19, 2021)

Got it. Thanks to all. And to all a good night (or afternoon…or morning).


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## Feral Feline (Jul 19, 2021)

🥱It's 3am here and I've gotta be up in 3.5 hours...😴


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## Coda (Jul 19, 2021)

Mod done and successful. Thanks to all.


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## Coda (Jul 20, 2021)

Update: I’m still running the pedal through its paces. D2 engaged and no diodes are definitely good settings (and different). However, D1 engaged is similar to no diode. There is a difference, but it is very subtle. No diode is more of a crunchy fuzz distortion, D1 engaged is that, plus a bit of splatter. I’m thinking of swapping in the asymmetrical “figure b” Schottkey/LED set up doe D1. I could also add another switch that would allow me to go Ge for D1 or the anti-parallel asymmetrical…


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## Coda (Jul 20, 2021)

A thought. The way I have it set up now, the  center lug is coming from the D1 anode pad. So when I switch to D2, I am in fact not getting D2, since the input is coming from D1, and not from D2, and this, does not follow the 4k7. In order to do this mod the way I would want, I believe I would need a 2PDT switch. Does any of that logic make sense?…


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## Coda (Jul 20, 2021)

Update again: I modded my mod. I realized that what I thought was happening wasn’t happening. So, I redesigned it. I now have two switches (SPDT on/on). I have each diode hooked up to a switch. I can now have both diodes on (spec), D1 only, D2 only, or no diodes. I socketed everything, so tomorrow I can swap in the anti-parallel rig…


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## frankthe669 (Mar 2, 2022)

Hey Coda, could you upload a diagram of that mod?


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## Coda (Mar 2, 2022)

I don’t know about a diagram (I barely passed Finger Painting), but I can definitely talk you through it. It is much easier than it sounds…otherwise I wouldn’t have figured it out. Let me review it a bit and I’ll start fresh.


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