Pull down resistor

[gtangas]

So i have a few questions on the usage of the pull down resistor that some effects use

I was watching some videos on youtube that explain the pull down and the pull up resistor.

On the case of the pull-down my conclusion is that the purpose of the resistor is to discharge to ground any current when the circuit is off. Current is lazy so it flows to ground, the flow route, Right?

The usage of a pull-down resistor helps in any way to prevent things like the pop that some effects make?

What are the other advantages of using it?

Thx

[garfo]

i believe that is the main advantage.in passie circuita like bypass loops you wire a 1 m resistor from input jack in or out,or both, to ground.but in sone builds like lets say the sea urchin,it worked better for me to wire a resistor from the out on the board to the ground on the circuit.

[gtangas]

i believe that is the main advantage.in passie circuita like bypass loops you wire a 1 m resistor from input jack in or out,or both, to ground.but in sone builds like lets say the sea urchin,it worked better for me to wire a resistor from the out on the board to the ground on the circuit.

It's different solder a resistor on fx out on the board from solder ir on the output jack (tip to ground)
The only difference that I see is doing it before the footswitch

I'm having a issue with a sea urchin that I can't kill the pop (I already solder the 100k and a 1M)

The first time I turn on the pedal it makes a big pop... The seconds times isn't so loud

[icecycle66]

Hey, me too.

[midwayfair]

"Pull down" refers to any resistor that connects an area of the circuit to low potential (in many cases, ground).

"Pull up" is the opposite, connecting to high potential.

In guitar effects, we tend to, somewhat lazily, use the phrase "pull down" to refer to the very large resistors at the input and output of an effect. But biasing resistors are also pull down and pull up resistors. Some quick examples:
R2 in the Kingslayer is a pull-down http://www.madbeanpedals.com/projects/Kingslayer/Kingslayer.pdf
R1 in the rangemaster is a pull-down http://www.madbeanpedals.com/projects/Rangemaster/Rangemaster.pdf
R1 in the Thunderpuss is a pull-up to a reference voltage. http://www.madbeanpedals.com/projects/Thunderpuss/ThunderPuss.pdf
R1 AND R4 on the Fatpants are pull-down: http://www.madbeanpedals.com/projects/FatPants/docs/FatPants.pdf

Edit: I believe, but I'm not entirely certain, that negative feedback resistors (e.g. between base and collector) qualify as pull-up to a reference voltage.

Basically, these are resistors that slow down bias changes when there's a circuit/voltage change on one leg of a semiconductor. Bias changes are responsible for all sorts of noises: scratching/crackle, switch pops, etc. The resistors have some effect on sound ("sparkle" and such), but that's their main purpose.

Main reason I had to learn this? Because I recently built an effect where I left off the pull-down biasing resistor on a stage FET and ended up with popping!

[gtangas]

Thx for explanation

I checked some projects files and yes we can find the pull down mostly in R1.

The urchin as a pull down on R1 (1M) and we still have pop.... I drill a hole on the board near the out put and solder a resistor to ground trying to kill the pop... It did help a bit but the first times that you engage the effect you still hear this bugger!

This is the second urchin I build and the first one I just add a 100k resistor on the output jack (tip to ground)  and it solve the issue... I can't say the same on this one