Footswitch Popping.

[steveyraff]

Hi.

Built a double pedal for someone and its popping when either footswitch is pressed. He also A/B'd it with another exact same one I built, and says that although they sound the exact same, he has to max out his volume to reach the same volume as the other one set to 12 o'clock (all other settings the same).

I am not sure if these two issues are connected? However, the popping is very loud. I've made quite a few of these and I've never heard popping before, so I am not sure what could be wrong.

I have also disconnected the LED's and eliminated that as an issue.

I will post the layout I am using and also the offboard wiring I am using:

[R.G.]

Popping is nearly always a sudden shift in a signal's DC level.  If I had this problem, I'd put a meter on the signal output of the effect circuit and see if it was less than 10mV dc. Anything more than that will be audible as a click or pop, especially with hard-metal switches.

There are other things, but that's where to go first.

[Beo]

Any reason why a switcher box like this couldn't just have in series capacitors on the inputs and outputs, maybe with a center voltage pullup? Is the concern that depending on what pedals get hooked up, you inadvertently create a tone filter or impedance mismatch?

[steveyraff]

Popping is nearly always a sudden shift in a signal's DC level.  If I had this problem, I'd put a meter on the signal output of the effect circuit and see if it was less than 10mV dc. Anything more than that will be audible as a click or pop, especially with hard-metal switches.

There are other things, but that's where to go first.

But what would be the possible causes and solution to such an occurrence ?

[amptramp]

If a coupling capacitor has some leakage, the voltage will go to some level other than what it should be.

If the 3DPT switch has contacts that transfer over with the LED being the last to switch, this could introduce noise.  It is generally not possible to determine which pole switches first or which switches last, so some builds may be OK but not others.

[R.G.]

But what would be the possible causes and solution to such an occurrence ?

Anything that leaks some DC into the output wires. Yes, there are many things that can do that. Most pedals use electrolytic capacitors on the output to block the internal DC levels. Electrolytic caps leak some current all the time, so they need a pull down resistor on the order a 1M or so to pull the leaked current down to nearly 0V. It's much worse if you get an electro cap in backwards. This lets it leak hugely, as well as eventually killing the cap.

Inputs to pedals can leak current back out as well. It's rarer, but does happen.

External issues like getting the wiring wrong and connecting the signal lines to something that puts a DC level on the wires from the outside. Finding this usually involves a great deal of tracing wires and thought, especially with hard-switches involved, or disconnecting and re-connecting one at a time to find it.

But a big first step is finding out if this is the problem. Get out your meter. It's faster than the time you'll spend typing about it on the net.

[PRR]

> what would be the possible causes and solution to such an occurrence ?

There's a damp-spot in my cellar. What are the possible causes?

Cracked foundation. Bad roof flashing. High-high humidity. Leaky pipes. Weepy pump-tank. Condensation on pipes. Cat pee. But you have to question each theory until you confirm or deny it. This may mean moving stuff around. Or just upgrading several possible causes. (I may as well wrap the pipes against condensation, because I know that is some of the damp. If that is not a complete fix, go on the roof or question the cat.)

Once you find the cause, the solution may be clearer.

[steveyraff]

Thanks all,

Haven't had a chance to have a look into this one yet as I've been snowed under with other studio work lately.

Its hard to set the time aside to problem solve this one. I'm starting to wonder would just changing all the caps be a quicker solution to finding out if one is leaky lol   

[steveyraff]

If a coupling capacitor has some leakage, the voltage will go to some level other than what it should be.

If the 3DPT switch has contacts that transfer over with the LED being the last to switch, this could introduce noise.  It is generally not possible to determine which pole switches first or which switches last, so some builds may be OK but not others.

I disconnected the LED's and its still popping - so I am hoping that eliminates that, at least?

[Elijah-Baley]

I never used this dual wiring, but I have to use it soon. This is an annoying problem. I hope you can find the cause.

Check again all the wires?
I see the right footswitch is really close the tha jack. Some unwanted contact?
Did you try to put another truebypass pedal before and after this and see what happens? I could say if the external pedal doesn't cause the pop with non of the side of the king of tone so should be something wrong with the wiring of the two sides of the king of tone. Does someone agree with me?

[steveyraff]

Check again all the wires?
I see the right footswitch is really close the tha jack. Some unwanted contact?
Did you try to put another truebypass pedal before and after this and see what happens? I could say if the external pedal doesn't cause the pop with non of the side of the king of tone so should be something wrong with the wiring of the two sides of the king of tone. Does someone agree with me?

Checked my wiring multiple times. The footswitches are not making any contact with the jack.

[R.G.]

What was the result of checking the inputs and outputs of the effects for DC voltages with your meter?

[steveyraff]

What was the result of checking the inputs and outputs of the effects for DC voltages with your meter?

I haven't gotten back to you about that yet because I literally haven't had the time to go back to this problem since. I am really busy with my recording studio doing 12 hr shifts a day at the moment.

I briefly tested between the DC power lug and the circuit output. I forget the exact ready offhand, I think it was 8.5. I will be able to confirm these readings for you asap. Thanks for the suggestions. I am kinda just gathering info so when I do have the time to sit down with this I know all the things I can look into. Cheers.

[steveyraff]

Odd thing is, I've tried disconnected the 9v from each circuit one at a time. It doesn't matter which one is disconnected - both footswitches still pop quite loudly.

[steveyraff]

What was the result of checking the inputs and outputs of the effects for DC voltages with your meter?

Between the DC jack positive lug and the input/output jack tip lug = 9.33 

[steveyraff]

Just built another one of the same pedal. It does pop when either footswitch is engaged, but its a lot milder. Also, the one I am trying to fix which pops much more also has a lot lower output. I wonder if these two things could be related?   

[R.G.]

Probably. At this point, it would make sense to pull back and execute the stuff in "Debugging: what to do when it doesn't work".

Get two schematics, lay them out, start measuring pin voltages on transistors and ICs with no signal passing through. This will tell you a lot about what is and isn't right inside. In fact, it tells you everything other than the AC signal performance, and may even tell you why that isn't right.

[idy]

I'm not sure Stevey is getting this about checking for DC on the output (or input) jack (or wire from the circuit.)
You measure, using the DC millivolts setting, using your black probe on the ground and the red one on the in or out. You mqy encounter some non-zero value which will not be the supply voltage (like 9v) but will probably be in the millivolt range.

[steveyraff]

I'm not sure Stevey is getting this about checking for DC on the output (or input) jack (or wire from the circuit.)
You measure, using the DC millivolts setting, using your black probe on the ground and the red one on the in or out. You mqy encounter some non-zero value which will not be the supply voltage (like 9v) but will probably be in the millivolt range.

Thanks for the clarification. I'm all over the place lately with these 12hr shifts. Will double check that this evening and report findings. Thanks for explaining. Appreciate it!

[steveyraff]

I'm not sure Stevey is getting this about checking for DC on the output (or input) jack (or wire from the circuit.)
You measure, using the DC millivolts setting, using your black probe on the ground and the red one on the in or out. You mqy encounter some non-zero value which will not be the supply voltage (like 9v) but will probably be in the millivolt range.

Ok, using this method, set the meter to DCv range, 20m, black prob to the DC jack ground, red to the output tip jack the reading is 4.14

Red probe on the input tip jack and I just get a flashing minus symbol?