Eliminating TB "popping"

[Danny G]

What are some ways to eliminate the "popping" that happens with TB and a 3PDT stompswitch?  I've tried adding a 1M pulldown resistor across the input tip to ground.  Still pops pretty bad.

Ideas?

[RDV]

Try a pulldown on the output also.

RDV

[jplaudio]

Some switches pop more than others you can try a new switch to see if it improves.
If you wire the switch so the input of the effect is grounded when by passed you won't need a pulldown on the input side.Most non-buffered effects that have an output level pot don't need a pulldown on the output.
If you are switching an LED with the switch try moving the power switching function from the input jack to the output jack.

[Hal]

Try a pulldown on the output also. If that doesn't work go up in value on the resistors(like 4.7M).

RDV

isn't the purpose of the pulldown resistor to drain DC from the input and output caps when the effect is bypassed?  And therefore wouldnt a 1M resistor drain MORE DC, and faster, from the cap than a 4M7 resistor?

[RDV]

isn't the purpose of the pulldown resistor to drain DC from the input and output caps when the effect is bypassed?  And therefore wouldnt a 1M resistor drain MORE DC, and faster, from the cap than a 4M7 resistor?

Faster yes, but not more. I stand corrected.

RDV

[Paul Marossy]

Of the all the pedals that I have built (24 or so), only one had a "pop problem". It was fixed by adding a 1M pulldown resistor on the output as well.

[aron]

Don't forget that sometimes the pop is because of DC at the output. So it could be a missing output cap or leaky output cap. Measure the DC at the output.

[Narcosynthesis]

i think soe switches can have a build up of static in them that will make them pop

try stomping on it a couple of times before using it and see if that helps

David

[Jason M.]

I've tried adding a 1M pulldown resistor across the input tip to ground.  Still pops pretty bad.

Ideas?

The pulldown resistor must be connected to the input of the circuit in order to do it's job.
By connecting it right to the jack, it is not connected to the input of the effect when it is bypassed.
Connect the pulldown resistor to the input at the board or the switch lug that goes to the input of the board.

You may have to do that at the output too, unless it has a volume control at the output.

[R.G.]

Two points to Jason.

[Gilles C]

I've tried adding a 1M pulldown resistor across the input tip to ground.  Still pops pretty bad.

Ideas?

The pulldown resistor must be connected to the input of the circuit in order to do it's job.
By connecting it right to the jack, it is not connected to the input of the effect when it is bypassed.
Connect the pulldown resistor to the input at the board or the switch lug that goes to the input of the board.

You may have to do that at the output too, unless it has a volume control at the output.

Agreed, as long as you mean "By connecting it right to the INPUT jack, it is not connected to the input of the effect when it is bypassed."

When you connect a resistor to the OUTPUT jack of the AB box, it stays connected all the time to the input of the effect. That's where you need a resistor for sure.

But you also need to activate the switch a few times to stabilise the thing.

I also think that a 1M or even a 100K would be better to eliminate the pops than a 4.7M  :oops: You have to get rid of the dc as fast as you can.

Am I wrong or what?


Gilles

[RDV]

HHHHMMMMM, on 2nd thought use a 22M or higher. The bigger, the better.

                                                           

[Gilles C]

:lol:  :lol:  :lol:  :lol: I just remembered what's happening when we touch the 2 sides of a charged capacitor together. Sparks, pops, etc...

If I add a resistor, the spark will be smaller...

The bigger the resistor, the smaller the spark, and the smaller the pop...

:lol:  :lol:  :lol: :?  :roll:  :roll:

Nooooooooooo... it can't be.......... :oops:

[jplaudio]

The pops caused by capacitor leakage are not exactly the same as the spark you get when discharging a capacitor.
The pops occur when there is a difference in the DC offset level as the circuit is switched in. The offset level is a function of the capacitor leakage , capacitor size and time. The longer the capacitor has one side held at a open state the more charge can build up . This is why if you rapidly switch the effect on/off the pops diminish. The pop level increases in relation to how long the capacitor is held "open". The reason for using a high value resistor for a pulldown on the input is to limit the loading effects of the pull down resistor. If you have designed a circuit with a 1M input impedance and then add a 1M pulldown resistance you have effectively dropped the input impedance to 500k. The same principle applies to pulldowns on the output side. Too low of an output impedance can affect the tone of the effect.
The pulldown resistors do not "discharge" the capacitor but prevent a charge buildup by draining current to ground level.
If you wire the switch correctly you don't need a input pulldown. Also consider the leakage characteristics of the input/output capacitors. If the charge can build up faster than the pulldown can bleed it off you still have a pop.
In addition ALL mechanical switches have some bounce that can be heard in some cases. The only way to eliminate pops and clicks completely is to use a switch element that can switch slowly like an FET or LDR.