# Pull-down resistors vs popping



## moonlightpedalbuilds (Oct 9, 2019)

I am having some popping sound on the 3pdt switch on my Mercurial Boost. So I placed 2  x 1M ohm resistors on the in and out of the board. Same problem with my Chela.



Is this correct?


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## phi1 (Oct 9, 2019)

Looks right to me.  Very surprised these weren't included on the pcb...

The Chela does already have pull down resistors (the volume pot on the output side counts).  So, if you're having the same issue, it might be a different culprit.  But, you could try it on the input, maybe the 3M3 is too slow to drain the DC.


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## Nostradoomus (Oct 9, 2019)

If it still pops after you have a pull down installed, it’s your LED.






						AMZ - LED Popping
					

How to stop the pops in audio from LED current surges when switched.




					www.muzique.com


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## moonlightpedalbuilds (Oct 9, 2019)

Nostradoomus said:


> If it still pops after you have a pull down installed, it’s your LED.
> 
> 
> 
> ...



All good, this worked. Pull-down on both input and output. I’ll pull the LED on Chela and see if it’s causing the pop.


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## Chuck D. Bones (Oct 9, 2019)

I used to think that the pull-down on the input side is mandatory.  If the Stomp Switch shorts the board input to ground in bypass mode (99% of the ones here do that), then you don't need the input pull-down.  On the output side, the VOLUME control usually serves as a pull-down.  The Mercurial definitely needs a pull-down on the output.  Chela does not.  The pop you are hearing must be the LED surge.  You don't have to pull the LED to test it, just jumper the Stomp Switch so the LED is always on.  It's the ON/OFF transition that makes the pop.


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## falzhobel (Dec 4, 2019)

Old thread but, used one on a SeaBed delay output and it stop popping instantly.


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## phi1 (Dec 5, 2019)

falzhobel said:


> Old thread but, used one on a SeaBed delay output and it stop popping instantly.



Check if there is DC voltage at the PCB output.  (DMM black lead touch ground, red lead touch board output wire).

The Seabed has a 1uF Electrolytic as the DC blocking output capacitor.  I've recently had some trouble with electrolytics from Tayda leaking DC so much that there's about 0.3~0.5v on the output, which causes a loud pop when activated or deactivated.  In both cases where I had this problem, I replaced the electrolytic with a film (1uF MLCC, or in this case 100n film would probably work fine with no bass loss), and the pop was gone.


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## falzhobel (Dec 5, 2019)

phi1 said:


> Check if there is DC voltage at the PCB output.  (DMM black lead touch ground, red lead touch board output wire).
> 
> The Seabed has a 1uF Electrolytic as the DC blocking output capacitor.  I've recently had some trouble with electrolytics from Tayda leaking DC so much that there's about 0.3~0.5v on the output, which causes a loud pop when activated or deactivated.  In both cases where I had this problem, I replaced the electrolytic with a film (1uF MLCC, or in this case 100n film would probably work fine with no bass loss), and the pop was gone.



I'll check that. It makes sense since I only had the problem on one of the 4-5 sea bed I have in the shop right now.


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## jstreetny (Jan 30, 2020)

phi1 said:


> Check if there is DC voltage at the PCB output.  (DMM black lead touch ground, red lead touch board output wire).
> 
> The Seabed has a 1uF Electrolytic as the DC blocking output capacitor.  I've recently had some trouble with electrolytics from Tayda leaking DC so much that there's about 0.3~0.5v on the output, which causes a loud pop when activated or deactivated.  In both cases where I had this problem, I replaced the electrolytic with a film (1uF MLCC, or in this case 100n film would probably work fine with no bass loss), and the pop was gone.



Is one method preferred over the other? I'm asking because I know I have extra 1M resistors to make a pulldown, but I'd have to order more 1u MLCCs. I may have better electrolytic (as in, not from Tayda) as well.


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## phi1 (Jan 30, 2020)

I’d recommend adding a pull-down resistor to the output regardless of which cap you use. Although the MLCC and film types aren’t very leaky, so it might not actually be necessary. 

I had some electrolytics that were leaking so much that even with the pull-down resistor after, there was a pop. Changed to film or MLCC and the pop was gone. So the MLCC or film would be safer, but you might get lucky and the electrolytic give you no problem.


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## Chuck D. Bones (Jan 30, 2020)

I agree, a pull-down is always a good idea, unless you already have a volume control at the output acting as the pull-down.  1M is unnecessarily large for an output pull-down.  100nA of leakage will make a 100mV offset using a 1M pull-down.  That will make a pretty loud pop when switched.  With a 1uF coupling capacitor, you could go down to 10K pull-down on the output and not lose any bass.  Aluminum electrolytics are all leaky, some worse than others.  Tantalum is a good option if you want something that will fit the footprint.  Otherwise film or MLCC will work.


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## Kroars (Sep 9, 2020)

falzhobel said:


> Old thread but, used one on a SeaBed delay output and it stop popping instantly.


Came here for this.  Built over 40 pedals in the last year and have just now encountered the infamous “pop” when hitting 3pdt on one of the Seabed’s I built.  Thanks!


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## falzhobel (Sep 9, 2020)

Kroars said:


> Came here for this.  Built over 40 pedals in the last year and have just now encountered the infamous “pop” when hitting 3pdt on one of the Seabed’s I built.  Thanks!



Same here, I've done a lot of PedalPCB building and it was the first time I had trouble. 

I think the "Hot Cake"circuit, even if it is buffere, do somePop also.


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## TheSin (Sep 21, 2020)

falzhobel said:


> Old thread but, used one on a SeaBed delay output and it stop popping instantly.


What did you use on the Seabed? Mine is having the same issue. Pops loud when engaging.

Also have the same issue on one side of a Paragon I just built, not as loud as the Seabed though, but noticeable. Thanks!


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## falzhobel (Sep 22, 2020)

TheSin said:


> What did you use on the Seabed? Mine is having the same issue. Pops loud when engaging.
> 
> Also have the same issue on one side of a Paragon I just built, not as loud as the Seabed though, but noticeable. Thanks!



1M on both input and output side (directly on the Footswitch breakout PCB). I've done that again yesterday on a dual pedal I was putting a Seabed on. Stopped all POP instantly.


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## music6000 (Sep 22, 2020)

pedjok said:


> I am having some popping sound on the 3pdt switch on my Mercurial Boost. So I placed 2  x 1M ohm resistors on the in and out of the board. Same problem with my Chela.
> View attachment 1771
> Is this correct?


I built the Mercurial Boost & it is Silent as designed by PedalPCB, There is something else in this Build causing it to Pop!


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## falzhobel (Sep 22, 2020)

music6000 said:


> I built the Mercurial Boost & it is Silent as designed by PedalPCB, There is something else in this Build causing it to Pop!



Some Amp FX Loop are particularly affected by very little voltage. My Orange Micro Dark was popping with allllll circuits.... Maybe something like that ?


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## Kroars (Sep 22, 2020)

falzhobel said:


> Same here, I've done a lot of PedalPCB building and it was the first time I had trouble.
> 
> I think the "Hot Cake"circuit, even if it is buffere, do somePop also.


Right on man.  Thanks again!!


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## Robert (Sep 22, 2020)

music6000 said:


> I built the Mercurial Boost & it is Silent as designed by PedalPCB, There is something else in this Build causing it to Pop!



At one point there was no pulldown resistor on the output of the Mercurial Boost.    (that's how the schematic was drawn)

It has since been added, so that's probably why yours doesn't pop but his did.


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## music6000 (Sep 22, 2020)

Robert said:


> At one point there was no pulldown resistor on the output of the Mercurial Boost.    (that's how the schematic was drawn)
> 
> It has since been added, so that's probably why yours doesn't pop but his did.


Cool, Glad it was corrected.
Withe the Chela, Is that another EQD Resistor Value to Ground on the Output  again?


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## Robert (Sep 22, 2020)

music6000 said:


> Withe the Chela, Is that another EQD Resistor Value to Ground on the Output  again?



The 100K volume pot should cover that one, but I suppose reducing it to 10K might not hurt.


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## TheSin (Sep 22, 2020)

falzhobel said:


> 1M on both input and output side (directly on the Footswitch breakout PCB). I've done that again yesterday on a dual pedal I was putting a Seabed on. Stopped all POP instantly.


You referring to doing whats on the pic at the top of this thread? I wonder if doing that has any negative affect on the circuit? Thanks.


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## Nostradoomus (Sep 22, 2020)

Watch out for electrolytic capacitors on the output too, if they’re leaky they’re gonna pop.


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