Pull down resistors/line noise?

[Synsound]

I see that pull down resistors are mentioned in some builds and I am not entirely sure of the purpose. From what I understand they are placed between the input and the ground.
My question is what does this accomplish. My reason for asking is that I am getting line noise. I am still a bit new to this, but I would describe it to the hum/ his you may expect with a high gain input while the instrument is silenced. I would like to minimize this and was unsure of the best way.
Will this pull down method work or do I just need a gate?
I have circuits that I love the character of like the distortron and box of Rock
But this hum really gets under my skin so I just go back to the Purple Plexi 800 that has less character but also less noise. Is this just inherent?
Any help is appreciated.

[dbat69]

Pull-down resistors are useful to stop any 'pops' whe pressing the stomp switch.

The resistor allows any residual charge in the circuit to pass to ground (via the resistor) when the circuit is not in use, thus eliminating the pop when the stomp is next jumped on.  It won't stop hum.

The noise could come from a number of sources.  Have you tried the pedal with a battery only?  Have you used screened cable for the input and output?  Are all your grounds secure in the pedal?

[Synsound]

Ok, that makes sense. So I guess a gate is in order.

[rocket88]

Depends. Some pedals just have that characteristic of being noisy. It could be the power supply you're using. You may want to add an electrolytic cap from power to ground, if there isn't one already, or increase the value of the one that's there. That will act as a power filter and could help with the hiss.

[Synsound]

I will give that a shot. Thanx
Do you have a suggestion on the what value to start trying with?

[Silver Blues]

A current limiting resistor in series with the power supply rail may also help with your noise. Small value, 100Ω or something should do.

If there's no filter cap there currently, start with 47u. If that doesn't work, try 100u or 220u. If you still get noise after 470u, I'd start looking elsewhere for causes/solutions (like the CLR).