The dreaded switch pop

[rocket88]

this is an issue that that sometimes we find ourselves in, mostly when we don't have a pulldown resistor installed in an effect. i'm assuming that those reading this know the main/common cause when "true bypass" switching is being used, the sudden change in DC voltage when an effect is engaged and/or disengaged.

now, the reason for this post is based on an effect i recently built for a client, the modded phase 90. now, going through the tests at low volume, it sounded perfect, and for some reason i deceided to mess around with it at higher volumes, and the dreaded switch pop reared it's ugly head. so i threw a 1M pulldown from input to ground, since the output has a 150k to ground, i know it's setting the output volume, but figured it should help prevent the pop, and you know what happened? nothing.....not a damn thing.

i checked the input and output voltage and the difference is startling. input was .31V that decreases, showing capacitance leakage, output 4.86V stable. i haven't checked any other effect for input/output voltages, but that seems to be more of a difference then it should be. now, no one mentioned any switch pop issues with the effect over on the blog when it was verified, so i'm wondering could it be something else or should i add an output pulldown, 100k, similar to what has to be done to the ehx small clone.

obviously, it could be a crap switch, but they're the same ones i've used for years, so i highly doubt it. the other issue could actually be the LED, and by adding a cap to ground would help with the voltage change, but i really think it's the DC voltage change. i could just leave it as it could be the nature of the beast. the customer said he's fine with it, but i'm a bit of a perfectionist, so i would rather get rid of it if i can.

this isn't necessarily asking help, but i think this is an important topic to be discussed, since this does occur randomly with effects, and can be a frustrating thing when everything works perfectly, but you get popping.

so what experiences have you had with switch popping and cures you've done. it's not something that is really discussed when building, since we all assume that there are pulldown resistors, but not always.

[ξεναγος νεκροπολης]

hi zack!

as i was reading your post, i thought why not just try my phase90 right away. i've build the modded layout too.
in mine i can barely hear a pop if i unplug the supply while the effect is on, and then put it back. but after a few (2or3) "on-offs", the pop disappears and i don't hear it any more while on-offing(!) it.so not a big problem for me too.

anyway

the layout already has an 1M pulldown resistor.maybe that's why nothing happened. i once had a simmilar poping problem and it was from the LED...and from a messed up supply bomb i've wired...

the bad news...???
as i was checking this pedal, i got distortion in one possition of the script switch...grrr...i have to open it...!

[Muadzin]

I build me a very ambitious all in one looper once. It had 5 switches, two of them stereo. Selectable EP-3 preamp, repeaterbuffer, splitter (for the stereo. Signal chain went in -> selectable EP-3 preamp -> Loop 1 I build me a very ambitious all in one looper once. It had 5 switches, two of them stereo. Selectable EP-3 preamp, repeaterbuffer, splitter (for the stereo. Signal chain went in -> selectable EP-3 preamp -> Loop 1 -> Loop 2 (alternated between a dirt and clean loop, repeaterbuffer at the end f the dirt loop) -> Loop 3 -> send/return loop to AMT F1 preamp pedal -> splitter -> loop 4 stereo -> loop 5 stereo -> outputs.

Everything worked, but when I used on my pedalboard I got pops whenever I activated the stereo loops. I thought it was the 4pdt switches that I used so I replaced them with relay switches from THcustoms. Because while I might be able to live with a pop if its a phaser  or a dirt box, pops have a nasty habit of ringing out when using a delay. Yet still pops with the relays. And the pops only occured with switches 4 and 5. When I input the guitar signal in the return jack of loop 4 or the AMT-F1 return, no pops, when using the return of loop 3, pops. The problem really was in the 2nd half of the system.

So I reused my old three switch looper for the first three loops and created a new box for just the stereo loops. Output of the first looper goes to the AMT-F1 and then to the 2nd looper box, from where it now gets split and behold, no more pops when I activate the stereo loops.

I have no clue what caused the pops. I can only theorize that it was some weird kind of impedance or ground loop thing of having too much stuff in one box.-> Loop 2 (alternated between a dirt and clean loop, repeaterbuffer at the end f the dirt loop) -> Loop 3 -> send/return loop to AMT F1 preamp pedal -> splitter -> loop 4 stereo -> loop 5 stereo -> outputs.

Everything worked, but when I used on my pedalboard I got pops whenever I activated the stereo loops. I thought it was the 4pdt switches

[induction]

Output at 4.86 VDC indicates a build problem. Need pictures.

[rocket88]

lol, well i didn't expect this to be a debugging thread. since posting i've been going through the pedal checking for issues. i originally i had a 10uF and 4.7uF cap in parallel for the LFO to make up the 15uF. i had ordered some 15uF caps, which showed up yesterday so i decided to replace it, and the pop is completely gone. so something happened to the caps.

definitely interesting that the effect worked, but had a pop as a result of a a bad/dead cap. again this is why i wanted to get a thread going about switch pops and causes. most of us would not think of something like what the issue that caused mine was.

ξεναγος, i shouldn't have said anything. it's always my fault around here. i am the Emperor of the Ge Deathstar, in case you forgot. lol

side note. anyone who built the ehx small clone chorus and has an lfo click, i've found a solution randomly. i was messing around with some of my effects, and took out my old modded DS-1 and put it in front and the tick was good. so just putting a buffer in front of it will stop it. so while there is a switch pop due to no having pulldown resistors, just add them to the switch and you're good, but the click is equally fixable.

Muadzin, that's exactly what i'm talking about. it's at the dumbest times that it shows up and for the most case it's hard to figure out what the hell is going on. it's just beyond frustrating.

[motterpaul]

Just FYI - I was looking for articles on forward voltage when I saw a good article on alternative ways to power up LEDs and avoid the dreaded pop.

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

When you power on a pedal the power goes through the LED, which is a diode that will hold a charge until it lights up,  - resulting in the pop sound.

Slowing down the rate which the LED lights up helps to eliminate the pop. The fix does involve a 10uf cap, so there you go.

There is also this for "high-gain" pedals: http://www.muzique.com/news/noisy-3pdt-switches/

I have an issue like yours rocket...

I built a blowerbox for my bassist, and there's a huge switch pop when engaging... Allthemore disturbing as the sound guy use only the bass D.I. sound...

Tried the led alternatives but had no success, I even disconected the led and pop still here! So now i'll try to mess with input and output caps, thanks for the tip!

[rocket88]

i hear you. luckily mine was just a faulty cap in the lfo, not something i would have inspected as the cause to be honest, it just so happened i wanted to replace the 2 series caps with 1 15uF cap. not sure if you read this before, but the best article on switch pop i've read is from none other the r.g. keen. link.

two main causes according to r.g., not counting one if you're using a relay, are

1. the input and output capacitors on the effect will always leak a little bit of DC, no matter how good they are. When the pedal is bypassed in the "classic" true bypass circuit (see "The Technology of Bypasses" at GEO) both capacitors are open circuited. While they are open, the leakage will shift their DC voltage a little, and when the pedal is un-bypassed again, the capacitors have to charge back to their in-use voltages. That sudden voltage difference and the charging current that brings the capacitors back to the working voltage is heard in the amplifier as a pop. If the effect has any gain, the input capacitor pop is further amplified by the gain of the pedal into a bigger pop.

2. finally, for true-blue mechanical switches, if the signal itself is not at exactly zero volts when the mechanical contacts touch (and bounce a few times!) this makes an instantaneous change of signal level just because the **signal** is suddenly connected. This tends to be smaller, but some people hear this as a pop. If the switch  bounces a bunch, there is a whole train of these on-again, off-again signal bounces, so there's a "crackle/pop" sound if it's really bad.

check what the voltage is at the input and output when you give the pedal power. it may be something faulty like what happened to mine, or it could just be the switch.

[motterpaul]

How about replacing them with tantalum?

(the electrolytic I mean. Tantalum supposedly does not leak as much)

Ok,

Mine would definitively be within number 2 as it pop both when turned on and off, and output voltage is about 3,2 v when turned on (and 0V turned of).

I'll try to change that output cap! (could it be another bad cap ?)

Changed the output cap and pop almost disapeared now!!

happy

The faulty was a cheap electrolityc I got from tayda...