Filtering RF from distortion pedals

[Labaris]

Hi everyone,

I'm working on a Marshall Shred Master clone (wich is going to get modded very soon ) and I got it mounted on protoboard right now. The problem: I can hear many different noises when the guitar is muted, specially with gain at max.

I already change the voltage divider resistors for a 10k pair and added a 100pF cap right after the input series capacitor. Both things doesn't seem to reduce the noise very much.

I would like to get some advices in this matter and hopefully get the theory behind it too, if possible.

Thanks a lot!  

PS: This is a schematic of the pedal

[R.G.]

If the circuit is on a breadboard, it may be impossible to keep RF interference out. This is the purpose of grounded metal boxes - they shield out radio and AC power line hum.

[Labaris]

If the circuit is on a breadboard, it may be impossible to keep RF interference out. This is the purpose of grounded metal boxes - they shield out radio and AC power line hum.

Thanks. That's the information I have, in fact all my pedals are built in metal boxes.
But, let's say the noise persists even with the pedal boxed. ¿Which parts of the circuit I need to look at in that case? The thing is, noise never leaves distortion pedals completely, isn't it?

[PRR]

You can never get away from hiss; only manage it.

If you get *radio* when everything is shielded, there is a problem with your shielding.

If you get power-line hum or buzz, shielding and power-supply filtering. (The way an electric  guitar works, you can never get away from all power-trash unless you can play far out in a field on batteries.)

[Labaris]

Thanks for the answers.

Shielding and power-supply filtering are standards I understand and try to apply always.

The question that I have is more related to circuit design. I'm trying to find standards methods to reduce "self" noise in a pedal.
Gain stage, I guess, it's the most critical part in terms of noise creation/capture/transmission. So, what is a good way to add noise filters and shielding to a circuit?

Thanks again.

[J0K3RX]

Thanks for the answers.

Shielding and power-supply filtering are standards I understand and try to apply always.

The question that I have is more related to circuit design. I'm trying to find standards methods to reduce "self" noise in a pedal.
Gain stage, I guess, it's the most critical part in terms of noise creation/capture/transmission. So, what is a good way to add noise filters and shielding to a circuit?

Thanks again.

Use "good" shielded wire (the kind with the foil wrapped around it on the inside) on the input and output jacks. Make sure the input and output are not close to each other, at all. Use shielded wire on the gain pot if the pot is not on-board. Put it in a box! Since I am no expert the filtering is usually done from looking at other similar circuits or getting expert advice...

[Labaris]

Thanks for the help.

Reading geofex.com I found this, where R.G. explains:

"(...) big external loops are going to be a problem.
So how do we bust the hum?
Easy - break the loops.
One highly effective way is to break the shield lines at one end of each signal cord connecting the effects."

I have this issue too, because I'm using a single-transformer 8 outputs PS. I have 8 pedals connected to it, but using 6 of the outputs (3 effects with daisy-chain).
So, I'm going to build a better PS with many transformers like the Spyder,

but

for now I want to implement a solution that helps to reduce noise with the current PS.

This sentence: "... break the shield lines at one end of each signal cord connecting the effects." makes me wonder: if a use only 1 daisy-chain for all pedals would it be the same as cutting the shield lines? Maybe I'll end up with an antenna but I don't know.

Thanks!

[Labaris]

There was a huge amount of noise coming from my pedalboard. Finally, the reason was an old PC monitor placed less than 2m away from the pedals and the PS.
It surprise me how big can the "magnetic noise". There's still some perceptible noise, but it's a lot less than the previous.

Thanks for the help to everyone! And keep your old monitors as far as possible from you!! 

[J0K3RX]

There was a huge amount of noise coming from my pedalboard. Finally, the reason was an old PC monitor placed less than 2m away from the pedals and the PS.
It surprise me how big can the "magnetic noise". There's still some perceptible noise, but it's a lot less than the previous.

Thanks for the help to everyone! And keep your old monitors as far as possible from you!! 

Old CRT monitors are horrible! They make all kinds of noise! Light dimmer switches do also!

[R O Tiree]

And fluorescent strip lights. On another forum (not "the other" forum, just "another" forum) it took us a while to figure out what one guy's noise problem was almost every time he engaged his dist pedal. Turned out his bedroom was above his mum's kitchen, and she had strip lights in there. When she wasn't in the kitchen, things were quiet.