*POP* goes the pedal

[maysink]

Some people say it's the power supply--fresh 9v battery vs. regulated, isolated 9vDC wall-wart. Some say it's the amp (this make vs. that model). Some say tie a 1M resistor between the tip & sleeve of the input jack.

I say it is the only complaint I have of DIY pedals. Boss (buffered) pedals don't have it. The few EHX ('true bypass') pedals I've used don't have it. My buffered Madbean SLAPCHOP (buffered pedal) has it. But nearly all gain pedal kits/PCBs I've made have an annoying POP when I stomp on them.

WTF is causing this? Is this my only option a 'click-less' relay as advertised on BYOC a few months ago? Is it a symptom of the standard blue 3PDT switch?

What say y'all?

[gtr2]

Are you taking about a pop through the amp or just the sound from clicking the footswitch?  None of my pedals pop through the amp, diy's included.

http://www.muzique.com/news/noisy-3pdt-switches/
http://www.muzique.com/news/pulldown-resistors/

If you go the silent switch relay route try this.  Cheaper than Deville's.
http://www.muzique.com/schem/bypass.htm

[madbean]

High gain pedals will definitely have a more pronounced pop, if there is one, because that small amount of noise gets amplified so much.

Pulldown resistors mitigate this by draining off voltage from the decoupling cap. The downside is that the pulldown resistors also affect input imepdance and there may be some cases where you do not want a high input impedance.

The relay is an alternative, as gtr mentioned. There are a few schemes you can use with LED indicators that can also help reduce that noise, too; http://www.muzique.com/lab/led.htm

[maysink]

High gain pedals will definitely have a more pronounced pop, if there is one, because that small amount of noise gets amplified so much.

I notice it more with gain-y pedals which I assume to be due to the sudden increase in signal hotness. I'd read the page on led popping and tried the 2 resistor & a cap mixed into the led but it did nothing for the pop. This was some time ago so perhaps I should revisit the idea. But is it all just the LED? I've never built a pedal w/o one...

I keep thinking of boss pedals and how an old ds-1 I sold would just leap into action w/o any popping--just instant ds-1 distortion. Didn't really care for the pedal but never forgot how effortlessly it spang into action.

I'm off to read gtr2s' muzique.com links.

[jkokura]

Interesting. I haven't had to deal much with popping in my DIY pedals, but my madbean porkbarrel was popping on me pretty bad the other day. I'll have to look into it a bit more but...

What would cause popping in a chorus pedal like that Brian? I doubt it's the wiring or LED's that i have, and it's not exactly a high gain pedal... I was using a regulated and isolated 9V power supply, so I doubt that it was the culprit. Could it be a cap? Or perhaps it is the LED... I don't really want to go poking inside there, but I don't like the Popping.

Jacob

[Myramyd]

My board is almost entirely DIY pedals and I use a regulated power supply only. The ONLY time I hear a *POP* when clicking on a pedal footswitch is when I'm at a location with a bad grounding scheme.

This also occurs for me ONLY when stacking gain (i.e. any pedal into a high gain amp channel, or multiple gain pedals into moderate or low gain amp channel, or when using a compressor and overdrive/boost together, etc.).

I would recommend testing the power outlets where you use them for a bad ground. Also, you might check your pedals with different amps to make sure your amp doesn't have a noise issue.

Or, it may be just your particular setup. For example, if you have any gain pedals turned up loud (volume/gain/drive) on the pedal itself, then the amp turned down low, you would be amplifying noises as well since you might have a very hot signal hitting the preamp.

Just some things to troubleshoot.

J

[jkokura]

Thanks J for your suggestions. I appreciate the help, but none of those are my issues nits a chorus pedal, the only pedal in the signal chain, my ground and amp are fine and I don't get any pop with other pedals, just this one.

Jacob

[CRBMoA]

A 3PDT switch, at it's core, it still mechanical. It is 'possible' that you have bouncing contacts in the switch.

I have never had an issue with popping in any of my builds, and I'm going on two years next month.

I built two power supplies from the discotinued GGG Isolated P/S project, and I use a One-spot for anything else I need to feed.

My main gig in in a 400 seat room, and I run my DIY board to this to FOH, and I haven't heard a click or a pop, ever.

[pauloman80]

A guy on another message board I'm on posted a guide on how to fix the pop in a 3PDT switch.  I haven't tried it myself just yet, but I'm very intrigued by it.  It's below, take a look.

[attachment deleted by admin]

[jkokura]

I might wire a switch like that and see if it would remove the pop in my Pork Barrel... If it removes the pop I'll be amazed and grateful! However, it seems like a lot of work for something that doesn't bother me all that much...

Jacob

[maysink]

I'm gonna try this arrangement on my next gain-y pedal as those are the ones I get the pop-yness. Thanks for sharing the pic!

[TB72]

Has anyone tried the above wiring scheme yet?

The Quasar I just built has these popping issues (first time I've ever had this problem...dozens of builds under my belt). I'm going to try it out and see if it does the trick.

Later...

[pauloman80]

I haven't even tried it yet, and I posted the dang thing.  Working on a Sunking right now, doing the true-bypass version.  Gotta wait and see what's what, gonna rock-it-before-I-box-it to make sure.

[dromilious]

Hello.I have Pop problems with most of my boost pedals and some distortion.When i plug dc in the circuit and turn on for the first time the 3pdt then it makes this pop sound.When i turn it to bypass and back to circuit signal the pop desapears.So it happens only the first time it takes dc.
P.S. i dont ground the input circuit at the bypass mode.Also i use 33 k resistors for my high brightness leds .

[Jack Deville]

The LED indicator circuit is not making your switch pop.
Period.  End of argument.
Doubtful?  Increase your decoupling capacitors in your primary power circuit, secondary voltage(s), bias supply circuit (if applicable), and of course that pesky LED indicator circuit.  Bump it up into the farad range and I guarantee, the only thing you'll have is too much capacitance.  Pops, clicks, thumps and all that nonesense will still be waiting for you to bang your head on the bench about.

If you are interested in the source of clicks, pops, thumps and other noise introduced by mechanical switching schemes, I'll begin to outline a few.  Take from it what you will, or completely dis-regard it and slap a "relay bypass system" in, because everyone knows, a relay is so quiet!  We'll talk about that in a minute.

Remember, mechanical switching schemes (sometimes configured for "true-bypass") are mechanical by definition.  Herein lies your first challenge.  I'll address the most common true-bypass schemes using the most common parts, as this is what most people on this board are likely to be interested in.

Your garden variety 3PDT switch is a heavy duty push-button switch.  It is designed to handle considerably larger currents than those that are present in most every effect circuit I've seen.  Because of this, large, heavy contacts and springs are used to break the current position and snap them into the next position.  Larger contact means more mass.  Means more inertia behind the contact as it moves, means more tension required to dampen the bounce as the contact settles into position.  This is our first concern to address.  Debouncing.  I'll save a 30 page dissertation and allow the parties interested to read up on debouncing, which is concern that is faced by any considerate designer.

The long and short of this is the switch must be properly debounced, or at a minimum, currents and voltages generated by the changing contact position must be eliminated/minimized.  This is a lot harder than you may think, especially when using a part that is not designed for signal switching.

Lets move on to the mythical "pull-down" resistor.

Why does everyone say "add a XM pull-down resistor?  Its simple really.  Nothing in this world is perfect and capacitors are certainly no exception.  A perfect capacitor would completely block the flow of DC once saturated/charged.  This action in itself would seemingly eliminate our concern with pull-down resistors.  However, nothing in this world is perfect and capacitors are no exception.  Even the best capacitor will bleed a little, even with the presence of perfect DC across its terminals.  We hardly have perfect DC, and we really don't have perfect DC in a guitar pedal.  Here's a simple example to illustrate the point.  I'll use a common op-amp overdrive circuit as an example:

Follow the golden rules for op-amps.  Both inputs must be at the same potential.  This never happens, but they will be pretty close most of the time.  In reality, the inputs will be constantly changing ever so slightly as they correct one another and eventually settle to near identical potentials.  These changes affect everything connected to their terminals, in this instance, one of the terminals of the input decoupling capacitor.  Because this terminal is changing, it follows that the opposing terminal of the input coupling capacitor is also changing as the potential across the capacitor must remain constant once the capacitor is charged.  If the terminal connected to the op-amp input goes up 0.1mV, the terminal to be connected to the switch must also go up 0.1mV, or close to it depending on a variety of factors I will not detail right now.  The inverse is also true.

A pull-down resistor works to ensure that the capacitor terminal to be connected to the switch remains close to ground potential so that when it is connected to the guitar/upstream circuit a large voltage offset is not present.  The key here is that the terminal is close to ground potential.

This leads us to another interesting aspect of mechanical switching:  time.

There is a period of time in a break before make switch where the contact is not connected to anything.  It is literally floating between the two contacts.  During this time, the contacts can be at ANY potential, and this potential can, and often is, changing.  When the contact snaps into position, that potential, which may or may not reach equilibrium with the new contact, is transferred onto the new contact.

Back to debouncing:  as the contact settles, it is making and breaking connection numerous times and the same phenomenon occurs over and over and over ad nauseum, until all energy is absorbed and the contact is at "rest."

This post is getting long, but I think the above points are enough to consider for the time being, and may offer some insight into the most common sources of switching noise.

As far as those "quiet relays" go, that is another subject.  I am happy to outline some of the considerations which affect switching noise in relay bypass circuits, and I'm also glad to explain some of the reasons that many of the DIY relay bypass circuits are, and always will:  noisy.

I hope this information is found useful and relevant.

NOTE:  Original post edited per request by jkokura.  Edited text highlighted in italic.