Plop issues

[fuzzo]

Hi guys,

Yesterday I modded an overdrive, it didn't "plop" at all but after this mod it does

This fu***** noise really piss me off.  Once I made a zvex sho clone and the bypass switch did this big noise everytime I switched it, a big "boom" in the speaker amp. I tried all things I could and nothing change. I've even do another booster to see if the circuit was guilty and it doesn't.

I suppect the poor quality switch 'cause some of my other pedals don't do that, the plop comes with the same brand footswitch (the "tawain" blue at Banzai), my Dunlop Wha and fulltone fuzz don't plop too. But maybe I'm wrong and the switches are good, So I'd understand what produce this really boring noise.



What produce this "plop" ? circuit design ? poor quality switch ? power supply ? and How I can definitively fix it ? 

Thanks

[R.G.]

Yesterday I modded an overdrive, it didn't "plop" at all but after this mod it does

Hmmm... let's see. It did not pop before you modded it and then did pop after you modded it? I wonder what could have caused the pop to start.   

Hey! Maybe it was the modification that made the pop start happening!!   

What produce this "plop" ? circuit design ? poor quality switch ? power supply ? and How I can definitively fix it ? 

I notice you've thought of everything that might cause it -except- what you did.

If it were me, I'd try undoing the mod. 

Or if the mod has to be there, I'd try measuring the DC voltage on the input and output pins of the effect both before and after bypassing to find where the DC's coming from.

[MikeH]

What mods exactly did you do?  Did you change the input or output caps?

[earthtonesaudio]

As always, for the most specific, best advice, please give specific information about what you did and what the problem is.  How did you mod the overdrive?  What overdrive is it?  What is the nature of the "plop?"  When does it happen?  Does it happen always in the same way? etc.

In general, switches are not defective.  Many people would be upset at always getting defective switches and never buy from a company again, so it's not in the switch maker's best interest to let faulty products out the door.  It can happen, but it's not the most likely thing.

The most likely cause of damage to a footswitch is excessive heat or physical manipulation during soldering.  Some switches are more tolerant of this than others, so some switches may work flawlessly for one person with one soldering technique, but not work for another person with a different soldering technique.

However, if you have no trouble switching the effect on or off, just a "plop" every time you switch it, it's probably not the switch at fault!  More likely is there is some DC on a signal coupling capacitor somewhere that is not referenced to ground, and switching causes a large and fast change in voltage, which translates to a short loud sound from the speakers.  Do you know about "pulldown resistors?"


One more time: http://www.diystompboxes.com/wiki/index.php?title=Debugging

[aron]

Usually I check for DC at the input and output of the circuit using my DMM. This will tell me if there's a leaky capacitor or some other problem. Use pull down resistors and ground the input of your circuit when not used. This has fixed a lot of problems with popping.

[fuzzo]

Actually isn't  really a mod. I've done an overdrive with two gain stage but I don't like the sound it produced. I changed it for a simple gain stage with a Proco rat tone with the second AOP in buffer (actully it's the same thing than Jetter gain stage).

What mods exactly did you do?  Did you change the input or output caps?

Yes did, with what I wrote above, I changed the input cap (BOSS silver cap) for a 100n film cap.

Do you know about "pulldown resistors?"

Yeah, I tried few things with my SHO circuit and nothing worked. I tried : Coupling cap with V+ , bypass with input connected to the ground when effet is off, 100R resistor after V+, with and without led indicator, input pulldown resitors, output resistor, both together. Always "plop".

In general, switches are not defective.  Many people would be upset at always getting defective switches and never buy from a company again, so it's not in the switch maker's best interest to let faulty products out the door.  It can happen, but it's not the most likely thing.

Yes, that would be weird.

But is not just this pedal, I made : DOD440 , mosfet AMZ booster (twice), SHO, Guss NPN  and all "plop" like hell instead of my bosstone clone or LPB1 don't do that.

Or if the mod has to be there, I'd try measuring the DC voltage on the input and output pins of the effect both before and after bypassing to find where the DC's coming from.

I gonna do that.

I'll install a coupling cap with 9V and a 1M resistor pulldown at input in my gus NPN and see what happen.

[MikeH]

Most of these blue 3pdts don't take a lot of heat well, and if they get overheated they can develop "plop" issues.

Plop, plop!  Fizz, fizz!  Oh what a relief it is!

[Mark Hammer]

What has not been mentioned is the use of an indicator LED.  This topic has come up many times.  If the builder installs a status LED that requires a large current draw (or larger than it truly NEEDS to be), that produces switching noise too.

There are a number of ways to fix that, but one of the simplest is just to use a superbright LED and stick a larger value current-limiting resistor (10k+) in to reduce current draw.  People tend not to think of this, but as far as your battery is concerned, current draw is current draw.  It makes no distinction between the audio and status-indicating parts of the circuit.

[Electron Tornado]

Or if the mod has to be there, I'd try measuring the DC voltage on the input and output pins of the effect both before and after bypassing to find where the DC's coming from.

How much DC voltage is typically needed to create a "plop"?

[R.G.]

How much DC voltage is typically needed to create a "plop"?

Well, a full size single coil pickup puts out 100mV. Anything bigger than about 10mV is audible, certainly. A diode drop is 0.6V.

[fuzzo]

Hi,

I fixed the plop of my Gus NPN boost, I installed a 1M R at input effet and a 100uF at 9V jack. Plops disappeared. But not in my overdrive pedal, I put the same 1M R at input but a 47uF at 9V, maybe the values of the cap is important and like Mark said, the led indicator used.

but one of the simplest is just to use a superbright LED and stick a larger value current-limiting resistor (10k+) in to reduce current draw

I use super brigh blue LED with 2K2 or 4K7 .

[Electron Tornado]

How much DC voltage is typically needed to create a "plop"?

Well, a full size single coil pickup puts out 100mV. Anything bigger than about 10mV is audible, certainly. A diode drop is 0.6V.

Thank you, that helps provide some persepctive as well.

Just a thought - could pickups that are a bit microphonic contribute to, or actually be the source of popping in a true bypass pedal?

[nelson]

When I have plop and splashback issues, I like to place a wad of toilet paper in the bowl.