3PDT Footswitch Popping Sound

[stringsthings]

Proceeding with the thought that the 1.5M was suspect......

Anyway, while I could get some sound out of it, I turned the pedal off and on several times and the pop was gone. When the pedal turned on, I could definitely hear the volume get louder, so I know the pedal was working.....

sounds like your getting close to the problem here ! .... if the problem is this resistor, i would remove the old resistor and solder in a known good one ..... ( two equal resistors in parallel divides the resistance by 2 .... so putting a 1.5M in parallel with a 1.5M = 750K ) .....

[meltunes]

Hi Guys -

Steve: when you wrote "But I'm also adding a 2.2M resistor in between the 3PDT switch input lug (A2) and the PCB circuit board's input pad."

... did you really mean 2.2M as in mega ohm, or did you mean 2.2K?

Ron: thanks your details for a wiring scheme... I will need to translate what you wrote into a diagram grid before I'll really be able to understand the wiring layout.

Looks like I have a couple things I will try over the weekend... I'll post back what I find...

Mel

[Steve Mavronis]

Steve: when you wrote "But I'm also adding a 2.2M resistor in between the 3PDT switch input lug (A2) and the PCB circuit board's input pad."  ... did you really mean 2.2M as in mega ohm, or did you mean 2.2K?

A 2.2 megaohm "pull-down" resistor to help with grounding where one lead is in the direct path between the PCB input pad and the 3PDT input (A2 in the case of my diagram) and the other end of the resistor goes to a ground lug of the stereo input jack assuming it is grounded to the metal case. It's just to help with noise when unplugging or plugging in a jack and maybe with switching between bypass and effect somewhat.

Otherwise, from the DIY Stompboxes FAQ (http://www.diystompboxes.com/wiki/index.php?title=DIY_FAQ)

Pops when switching, even with pulldown resistors

From R.G. Keen

There is a weak link in the power/ground setup in most effects using stereo jack switching. You can get pops when switching the relatively high LED current even if you have pulldown resistors on both input and output caps.
The culprit is ground noise. The ground noise happens when the sudden start and/or stop of current in the LED makes the signal ground voltage change suddenly. +9V decoupling may not help, and may make it worse.
The ground noise comes from our friend, the stereo jack ground switch. If your jack is new and the plug is new, things work great. When dirt, oil, crud, bar funk, and other nasties build up on the ground ring of the input jack and the second-channel contact that supplies ground through the plug into the input ground ring, and thence to the effect board, the resistance through that path can get high enough to make a noticeable pop when the LED current starts and stops.
This sudden transient is worse with mechanical switches because they really do go from fully off to milliohms of resistance in zero time when the metals contact. The sudden "ground bounce" can flow right into the input of your effect, and it doesn't take much to hear a pop from the input of a gain-of-a-zillion MegaBlaster.
Also another thread on popping. [See the post by R.G. http://www.diystompboxes.com/smfforum/index.php?topic=68210.0]

What to do, what to do??

(1) Clean your plugs and jacks. Yep, and do it again. And again, every so often.(2) Use the OUTPUT jack for power switching - it's less sensitive by the gain of the pedal.
(3) Use the GEO scheme for cold-switching +9V by using a PNP transistor with it's base tied through a resistor to the stereo lug on the input or output jack, and the battery minus tied directly to the board. The PNP transistor only lets +9 through when its base is pulled down by the plug in the jack, but this current does not change noticeably when the LED is started, and so any ground bounce is only through the hard-soldered milliohms of the battery lead, and is much, much smaller.
See the power supply switch in the Neutron filter at GEO or at GGG, or see the positive 9V switch in [1] for how to hook up the PNP.
original thread on popping.

[meltunes]

based on the thread Steve provided, I have a couple things to try...

1) replacing the 100uF since I broke off one of the leads when trying to remove one side from the pcb, this might uncover a wrongly oriented cap
2) raising the resistor value on the FX out to > 1M ohm
3) replacing the switch itself

I'll post back what I find...

Mel

[meltunes]

Replaced the 100mfd cap, and replaced the 3PDT switch with another new one and nothing helped. Adding a higher value resistor on the circuit out didn't help any... I thought a new pull down resistor value at 1M ohm might help vs. the kit's original 100K value... but all it did was color my Tele's tone which I didn't like and it didn't help the loud pop when engaging the pedal and when bypassing it...

I still have the LED disconnected so that is not the source of the issue...

Would an inductor help placing that between the circuit out and the switch?  I think I read that somewhere, but as a electronics novice, I'm really grasping at straws and really just want to resolve this issue...

Does the mere fact that this pedal boosts my cleans really nicely without any hum or noise indicate that I have a good build, besides the fact that I get a loud pop when pressing footswitch on/off?

Any ideas?

Thanks, Mel

[Steve Mavronis]

I ended up just using the exact 3PDT switch wiring from Gaussmarkov's page and did not add any pulldown resistor or anything. I had my wife's cousin test it on his 1965 Fender Deluxe tube amp pretty loud and whenever he switched between effect and bypass and back there was no popping sound at all. I guess Gausmarkov's grounding the PCB input when in bypass mode works, at least for my overdrive pedal. Give his 3PDT wiring a try. The only thing different than his diagram I did was place the LED resistor between it and the DC jack instead of between the LED and switch but that part order change should have no effect on popping as far as I know.

[meltunes]

For next steps... I'm gonna check voltages on the FET pins and make sure the output capacitor 1.5mfd is functioning properly.

That is unless anyone has any other ideas for what to do... I've pretty much torn this pedal apart and put it back together... checked continuity of all the off-board wiring, checked all solder joints everything looks good.

Thanks for any advice!
Mel

[zombiwoof]

For next steps... I'm gonna check voltages on the FET pins and make sure the output capacitor 1.5mfd is functioning properly.

That is unless anyone has any other ideas for what to do... I've pretty much torn this pedal apart and put it back together... checked continuity of all the off-board wiring, checked all solder joints everything looks good.

Thanks for any advice!
Mel

If your only problem is the popping, why don't you try the 3PDT wiring that grounds the circuit in bypass (the wiring that Steve has suggested)?.  Or have you?.  That is the purpose of that wiring scheme, to eliminate popping.

Al

[meltunes]

Last night I went thru the pedal and measured voltages at various points thru the circuit... I've also attached a JPG image file that contains the voltage readings I took from the transistor.  I drew this since I wasn't sure what to call the various points.



Also, I read voltages from each of the capacitors. Based on what I observed, then I'd think there is something up with the output capacitor (C2) since its negative lead didn't read 0.0v like Potentiometer Capacitor (C1) and Power Filter Capacitor (C3), but I don't know if what I found is significant there...

This is what I found:

**Battery=8.9v
**Potentiometer Capacitor (C1 – 10mfd): Pos lead=1.0v, Neg lead=0.0v
**Output Capacitor (C2 – 1.5mfd): Pos lead=6.6v, Neg lead=1.3 to 1.4v (this reading increased over several minutes to 1.5-1.6-1.7v)
**Power Filter Capacitor (C3 – 100mfd): Pos lead=8.9v, Neg lead=0.0v
**Potentiometer Lugs: all three read 1.0-1.1v
**PCB Out to Switch (Blue wire to Switch Lug#9): 1.4-1.5v (this reading increased over several minutes in alignment with output Capacitor)
**Output Jack to Switch when footswitch pressed (Orange wire to Switch Lug #8): 1.4-1.5v (this reading increased over several minutes same as Blue wire readings)
**Output Jack to Switch when footswitch pressed again (Orange wire to Switch Lug #8): 0.0v (no voltage was observed)

**All other switch lugs always read 0.0v (no voltage observed) in either footswitch position engaged or bypassed – don't know if this is significant or not...

Do any of these readings seem to surface where the issue with the popping is?

Thanks, Mel

[amptramp]

Below are the kit's documents... perhaps you guys will see something here that will help...

I have quoted the schematic and layout here so everyone on this page can follow what you are trying to do.  The output capacitor negative lead should have very little voltage - it looks like a leaky capacitor.  You can get film capacitors in this value that are not much larger physically than the electrolytic and would have almost no leakage.  If this is a tantalum capacitor, it appears to be damaged because the tantalum pentoxide dielectric film inside should be pinhole-free and therefore very low leakage - that's the advantage of tantalum.

[meltunes]

To bring this thread full circle... over the weekend I replaced the output capacitor with another known good one (used a 2.2mfd). I took voltage measurements at the output capacitor's negative lead and its voltage reading was now 0.0v. The pcb out at the switch lug #9 and the output jack connection at the switch lug #8 both measured 0.0v also.

Just for good measure I added in an inductor on the LED positive lead (instead of the resistor-capacitor combo posted on www.muzique.com/lab/led.htm, which also works quite well, only I wanted to solder in one component into the line instead of two components).

Voila! No popping sound when bypassing/engaging the pedal... even with the potentiometer turned all the way "to 11"...

Thank you everyone who helped me along the way, working thru the various steps to troubleshoot this problem...

I have the pedal on my pedalboard now and it sounds awesome! Nice clean volume boost and actually makes my amp quite loud.

Now I'm ready for my next pedal build.... I'm hooked!

Mel

[seedseed]

I have tried that muzique technique for led popping and it does not work. especially if your building a overdrive pedal. What i don't understand is why people don't use a cheap inexpensive pnp transistor to switch the LED so that does the job. I would assume you wouldn't get a feedback through the earth to get a popping

[Barcode80]

I have tried that muzique technique for led popping and it does not work. especially if your building a overdrive pedal. What i don't understand is why people don't use a cheap inexpensive pnp transistor to switch the LED so that does the job. I would assume you wouldn't get a feedback through the earth to get a popping

what i don't understand is how so many people have successfully used that circuit of jack's on all sorts of effects, including overdrive, and have made it work, yet you claim it won't? The circuit isn't even attached to the effect circuit, so type of circuit is irrelevant. short of a bad cap or voltage leaking to the audio path some other way or massive current pull from the LED from using too large of a current limiting resistor (which still can often be solved with jacks' circuit), there isn't much pop the circuit won't solve. there is a problem elsewhere if it doesn't solve it.

and i don't think it's the parts cost as much as it would require more than just the transistor (like a couple of resistors and whatnot) to do it. for beginners especially, it can be pretty darn easy to overheat a transistor while soldering too. jacks' circuit utilizes a cap and two resistors, the "tanks" of the effects component world that it takes a LOT more heat to damage.

you can't argue with results, and a large number of us have used his pop reduction circuit with great results.

[aflynt]

Could I interject a question into this discussion? For the AMZ popping circuit, does the negative lead of the cap go DIRECTLY to ground or should it be wired to the same lug of the switch that the negative lead of the LED goes to? I read somewhere that it was the latter, but the diagrams in the original writeup seem to indicate otherwise:

http://www.muzique.com/lab/led.htm

Just wondering because I tried it on a son of screamer build that was popping and it popped when being turned off one way and popped when being turned on the other. I also noticed that the led faded in when turned on wired one way and faded out when turned off when wired the other way.

-Aaron

[Pomodoro]

To bring this thread full circle... over the weekend I replaced the output capacitor with another known good one (used a 2.2mfd). I took voltage measurements at the output capacitor's negative lead and its voltage reading was now 0.0v. The pcb out at the switch lug #9 and the output jack connection at the switch lug #8 both measured 0.0v also.

Just for good measure I added in an inductor on the LED positive lead (instead of the resistor-capacitor combo posted on www.muzique.com/lab/led.htm, which also works quite well, only I wanted to solder in one component into the line instead of two components).

Voila! No popping sound when bypassing/engaging the pedal... even with the potentiometer turned all the way "to 11"...

Thank you everyone who helped me along the way, working thru the various steps to troubleshoot this problem...

I have the pedal on my pedalboard now and it sounds awesome! Nice clean volume boost and actually makes my amp quite loud.

Now I'm ready for my next pedal build.... I'm hooked!

Mel

Hi Mel!

I'm glad you fixed your popping problem. I've bought and built exactly the same pedal as you and I am very satisfied with it too. But I'm meeting exactly the same popping sound problem as you. So I was wondering: in the end, what did you exactly modify from the original GGG-kit? Just the C2 capacitor? I don't understand very well your add of an inductor on the led positive lead? Could you please say more about it? (I'm also a DIY newbie...)
Many thanks in advance.

Tom

[Pomodoro]

Changed my output cap (C2) for a new one (2.2µF) and it does work perfectly now!
@Mel: Thanks for your help and your PM.

Tom