switch popping

[oasisman]

Hey there I'm new to the forums.  My name is James and have been reading through the forum last couple days.  It seems like a great community here.

I'm having a problem I have probably built around 10 pedals, and every pedal will pop randomly when engaged/disengaging.  It can be very random some times its silent some times it will pop on every cycle.

I have read everything I can find on the net about pull up/down resistors, changing input caps and they all; I have found useless.

I would like to try out a boss/ibanez style switching as they are dead silent. I know they are not true bypass and will need more circuitry, but I am at a point when I can not stand the popping any longer.  If someone could set me in the right direction for the buffered fet based bypass, and how to incorporate that into existing layouts I would greatly appreciate it.

Thank you

James

[Muadzin]

Thomas at THCustoms sells several true bypass relay style switching systems. At the Madbean forums they say he's the expert on such matters. You could ask him on the Madbean forums, he has his own subforum there.

http://diy.thcustom.com/

http://www.madbeanpedals.com/forum/index.php?board=48.0

[induction]

If all of your builds pop, that suggests a systematic error. I'm afraid I don't know much about boss style switching, so I can't help there. But if you're interested in tracking down where the pop is coming from you can post some photos of your builds and we can take a look.

[oasisman]

Thanks for the quick answers guys.  I've checkes that guys link and he has a section about popping.  He says it can be from bad cables as well, that could be my problem as my cables are not very good.  I'll have to join mad bean to view his thread. My thoughts on relaying switching is that if the pedal pops with a dpdt switch it will still pop with a dpdt relay, is this not the case?

I'm pretty sure my pedals are all wired correctly I'll post pictures later I am at work right now.

Thanks for you help so far!

James

[Frank_NH]

Probably the best answer for you:

http://www.geofex.com/Article_Folders/box_pop.htm

If you want to get to the bottom of the problem, I would make sure to do all testing in isolation:  guitar-->stompbox-->amp.  If it pops regardless of the amp and guitar, then the issue obviously lies in the stompbox.  You can then test the power supply and look at remedies like pulldown resistors and capacitor mods.  Check all your ground wires too (especially those going from various places to the box ground point) - may be something going on there.

[oasisman]

http://i60.tinypic.com/27ywcom.jpg

Here is the latest pedal I built, its a 3 band eq by Harold and it works great, apart from the damn popping.

 I'm sure my wiring is all correct. But if anyone can see a problem please chime in.

I use dpdt switches as I don't like using leds very much and if I use one I use the millennium bypass.  This effects switch is wired with input grounded when bypassed and the circuit already uses a pull down resistor.  This is pretty much how all my pedals are built.

I really love this hobby but the popping on the switch is really making me not enjoy it as much.

Also as suggested I have tried another amp and a different leads but still the popping remains.

Thanks
James

[Muadzin]

Do I see it correctly that the pulldown resistor is situated at the input jack? If so its before the bypass switch. And if memory serves me right it should be after the switch at the start of the circuit. Which is why so many circuits have a 1M resistor going to ground at the beginning of the circuit.

[Silver Blues]

Indeed a pulldown resistor mounted at the jack will accomplish nothing. If this is the case, it would explain your popping issues.

[oasisman]

The pull down resistor is mounted on the vero from input to ground not at the input jack.

I was thinking it could just be the swiches I use are very loud? I use alpha dpdt pcb mountable one, any one else use them with good results?

[induction]

I have two questions about the photo.

1. It looks like the input jack is not grounded. Is that correct?

2. The input switching looks backwards to me. If we label the switch lugs like this:

1    4
2    5
3    6

(keeping the orientation of the photo). Then your input jack is going to lug 2, your circuit input is going to lugs 1 and 6, lug 3 gets ground via the output jack, lug 4 gets circuit output, and lug 5 goes to the output jack. Can you confirm this or set me straight?

If I'm right, then your effected signal should work fine, but I'm a little surprised that you get bypass output at all, since your output is coming from the circuit input, which is not connected to the input jack.

My best guess at what's going on (assuming I'm interpreting the photo correctly) would be that points 1 and 2 combine to give you an inverted bypass signal. When you switch to bypass, your signal from the input jack gets dumped to ground, and your output jack gets switched to the circuit input, which is grounded through the input pulldown on the board. So maybe your signal is at the output jack is coming through the sleeve from the ground wire, while your 'ground' is coming through the tip. This would mean your signal is inverted and maybe has some DC offset, which could explain the pop. I would also guess that your bypass volume is quieter than the volume you'd get from a cable direct from guitar to amp.

Or maybe I'm just seeing it wrong.

[oasisman]

You are correct the input jack is only grounded by the enclosure.

This is the diagram I use for bypass.


And looking at the photo it look the same as mine.

Unless that diagram has any faults?

EDIT actually looking at mine I do have the effect in and out reversed.  I must have just messed that up when rewiring the switch after I tried a few more that I have.  I'll rewire them after work and see if that is causing me the problems.

[induction]

Cool. Let's hope that sorts it out. Let us know how it goes. Just to be clear, it is the effect send and the input jack that appear to be reversed. You'll want to swap the green wires attached to lugs 1 and 2, leaving the jumper between lugs 1 and 6 as it is.

I recommend including a dedicated ground wire on the input jack, even if the jack sleeve tab is shorted to the enclosure. Jacks tend to wiggle loose, usually mid-gig, and cause sputtering or outright failure that is difficult to locate. Also, the interface between dissimilar metals tends to develop thin layers of corrosion due to chemical interactions between the metals. This corrosion can cause a loss of conductivity, and the pedal will fail.

Many people use the enclosure for grounding because they want to avoid ground loops, but ground loops inside pedals are rarely a problem in practice. It's better to use a star grounding point (I use the input jack sleeve) and attach all other grounds directly to that point. That minimizes ground loops but provides a solid ground connection that is less likely to fail in the long term or have contact resistance problems in the short term.

[oasisman]

I tried swapping the wires and still a extremely loud pop on every cycle of the switch.  I don't quite no where to go from here really only thing I can do is try a different switch perhaps or find an alternative bypass method.

Thanks everyone for your help!

[Frank_NH]

I was going to also recommend trying a new, good quality switch (even a 3PDT).  There's possibly something mechanical which is inherent to your switch which is causing the pop.  I've used only good quality 3PDT switches from Mammoth Electronics and I have not experienced any pops on my builds.

[induction]

Do you have a DMM? If so, measure the DC voltage at the input and output when engaged and when bypassed. You can just plug in a cable and measure the difference between the sleeve and the tip. Use a low (mV) setting on the DMM.

[Frank_NH]

An interesting read...

http://www.mrblackpedals.com/blogs/straight-jive/6629778-what-really-causes-switch-pop

[oasisman]

I do have one that will be my next step what am I looking for I assume it should read 0v yes?

Yeah I've read that page and tried the different bypass methods apart from the bottom part about the limiting resistors as it doesn't specify what values as it mentions ohms law to works them out but at the moment I don't really understand it.  

Again thanks guys means alot that you lot are helping me I'll definitely be contributing to this forum in the future.

[Frank_NH]

Try a quick experiment.  Put a 1 M resistor between the Effect Send lug of the switch (first row, second column) and ground (you can use alligator clips).  In your arrangement, the board output is floating in bypass mode, whereas the input is tied to ground.  I'm curious to see if this helps.  Otherwise, I'd try a new switch.

[oasisman]

Tried that and the pop got a lot louder.  I also tryed a few other dpdt throw switches I have laying around and the pop is exactly the same. So has me thinking it is not actually the switch.

[induction]

oasisman wrote

I do have one that will be my next step what am I looking for I assume it should read 0v yes?

Yes, it should read close to 0V both engaged and bypassed. Let us know what reading you get. This measurement is to help us figure out where the pop is coming from. If you have a pop with no DC voltage on either jack, then it's more likely to be the switch.

You can also disconnect the input jack and effect send from the switch and see if it still pops. That will help us determine if it's popping at the input or the output. But I'd start with just measuring the DC voltage on the jacks and see if we can get some answers that way. It's easier and less likely to cause complications.

Finally, how long do you hold the soldering iron on the switch lugs when you solder them? Overheating the lugs can cause popping. It's best to never hold the iron on a switch lug for more than one second.

For educational purposes, I'm going to share my thoughts about your popping problem:
This circuit has bipolar power (the Max1044 is a charge pump that creates a -9V supply for the negative rail.) This means that the input and output should be at 0V even without coupling caps. In principle, it shouldn't pop even without input and output caps. That and the fact that it has pulldowns on both the input and output both make me suspect the switch.

You also said that this happens on all of your builds, so I don't want to read too much into this particular circuit. A systematic problem like this means that the cause is probably related to something that is shared between all of your builds. That could be the switch or a consistent offboard wiring error.

Keep that DMM handy. Depending on what you report for the voltage on the jacks, I'll probably ask you for more measurements.