# Dumbloid (Special Overdrive PCB) - Switchable Clipping Diodes



## cgmason1986 (Jul 15, 2021)

I want to implement a switch to allow for a couple extra clipping options in the feedback loop. I'm not a fan of the stock op-amp clipping. Can someone take a look at what I've drawn up here and give me a sanity check - does it make sense? Is there another way to do this that you would recommend? Any ideas as to what kinds of diodes to try out? I'm going to socket these so I can swap in and out.


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## music6000 (Jul 15, 2021)

Looks good to me, ARE 1N4148 your choice of Diodes?
Your leaving C5 & soldering lead to each pad from solder side I Believe?


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## music6000 (Jul 15, 2021)

cgmason1986 said:


> I want to implement a switch to allow for a couple extra clipping options in the feedback loop. I'm not a fan of the stock op-amp clipping. Can someone take a look at what I've drawn up here and give me a sanity check - does it make sense? Is there another way to do this that you would recommend? Any ideas as to what kinds of diodes to try out? I'm going to socket these so I can swap in and out.
> 
> View attachment 13681


Maybe the best option is to move your LED & use that for your toggle switch ???


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## cgmason1986 (Jul 15, 2021)

music6000 said:


> Looks good to me, ARE 1N4148 your choice of Diodes?
> Your leaving C5 & soldering lead to each pad from solder side I Believe?


Thank you! I was going to play around with different diodes I've got a bunch from different builds. This may be a dumb question but are there different diodes that are better for different kinds of clipping? Pretty much everything I've seen so far uses either germanium or Schottky, what about Zener?

And yes the plan was to solder leads to the solder side of C5.


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## cgmason1986 (Jul 15, 2021)

music6000 said:


> Maybe the best option is to move your LED & use that for your toggle switch ???


Yep that's the plan!


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## music6000 (Jul 15, 2021)

If the pedal has plenty of Volume on tap in stock mode, you have a lot more options.
Led's being the Loudest to bat41's being the at the other end of the scale.
1N4148's being the most common being in the Middle so to speak.


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## jubal81 (Jul 15, 2021)

You can do it with a SPDT. I created a little breakout board for that and shared it on OSHpark. You can order the PCB there. Takes about 10 days to get it, depending on how far you are from Portland, Ore.

How it works: Remove the feedback capacitor from the pedal circuit and solder it to C1 on this breakout. Populate the diodes. Wire the two pads on this breakout to the pads for the feedback cap on the pedal PCB.


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## cgmason1986 (Jul 15, 2021)

jubal81 said:


> You can do it with a SPDT. I created a little breakout board for that and shared it on OSHpark. You can order the PCB there. Takes about 10 days to get it, depending on how far you are from Portland, Ore.
> 
> How it works: Remove the feedback capacitor from the pedal circuit and solder it to C1 on this breakout. Populate the diodes. Wire the two pads on this breakout to the pads for the feedback cap on the pedal PCB.
> 
> ...


Thank you! I'm going to give it a shot without a PCB, hopefully I can get it to work haha. I was thinking I had to cut off both sides of the diodes from the circuit, but forgot that cutting off just one side means there is no current (duh) so yes definitely can do it with an SPDT on-off-on. So that would look like this?


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## cgmason1986 (Jul 15, 2021)

music6000 said:


> If the pedal has plenty of Volume on tap in stock mode, you have a lot more options.
> Led's being the Loudest to bat41's being the at the other end of the scale.
> 1N4148's being the most common being in the Middle so to speak.


Gotcha - yea it's stupid loud already, I'll play around with some different diodes then, thanks!


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## jubal81 (Jul 15, 2021)

Yup, that's it.


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## cgmason1986 (Jul 15, 2021)

Alrighty I made a switchable op-amp/symmetric/asymmetric clipping selector with some strip board and bus wire. I went through a bunch of different types of diodes and found that the symmetric LED's have me the closest to the natural pedal sound - while smoothing off the decay of the notes, and then asymmetric I used the 1N5241B Zener diodes and they have a little more compression/distortion which complements this really well. There is a small volume drop going from stock to symmetric, and then a bigger jump from symmetric to asymmetric, but overall I'm really happy with it. Schottky and germanium diodes just didn't have enough volume. Thank you everyone for your help! My first modification.


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## jubal81 (Jul 15, 2021)

Really nice job on that little board!


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## fig (Jul 15, 2021)

That's slick!


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## cgmason1986 (Jul 15, 2021)

jubal81 said:


> Really nice job on that little board!





fig said:


> That's slick!


Thanks guys! Happy with it for my first time using a strip board and first time modding a pedal.


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## music6000 (Jul 16, 2021)

Well Done!!!


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## uranium_jones (Jul 16, 2021)

fuzzy wire?


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## cgmason1986 (Jul 16, 2021)

quality_jones said:


> fuzzy wire?


Push cloth wire, you see it a lot in pickups/pick guards. Don't have to strip the ends, just push the cloth back.


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## Feral Feline (Jul 17, 2021)

See the pushback-wire in "vintage-style" amp builds as well.


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## Tbguitars (Dec 29, 2021)

jubal81 said:


> You can do it with a SPDT. I created a little breakout board for that and shared it on OSHpark. You can order the PCB there. Takes about 10 days to get it, depending on how far you are from Portland, Ore.
> 
> How it works: Remove the feedback capacitor from the pedal circuit and solder it to C1 on this breakout. Populate the diodes. Wire the two pads on this breakout to the pads for the feedback cap on the pedal PCB.
> 
> ...


I will be doing this modification and was wondering if you could help me locate that feedback capacitor on the pcb.  This looks like a great mod!


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## jubal81 (Dec 29, 2021)

Tbguitars said:


> I will be doing this modification and was wondering if you could help me locate that feedback capacitor on the pcb.  This looks like a great mod!


C5


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## Tbguitars (Dec 30, 2021)

Thanks, so much


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## harmaes (Tuesday at 3:16 AM)

I was wondering if you've experimented removing the red led right after the tone in the second feedback loop of the opamp?
The Clay Jones overdrive that was an "inspiration" for the dumbloid only has clipping diodes in the first feedback loop:




Compared to the dumbloid (Special overdrive):


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