About 9v dc Filtering

[ntuncer]

Hello,

I don't know here is the good place to discuss but let me know if I need to move the post. My question is 9vdc filtering. I am checking different Analogman King of Tone, Prince of Tone schematics and I see some differences to handle 9vdc but I couldn't understand why. Could you please help me to clarify why they are different and is it very important to add extra components to filter 9vdc in those ways as below?

Here is The Pauper (Prince of Tone) and Paragon Mini (King of Tone without charge pump) 9V dc Filtering:


Here are another schematics (Aion Fx) which there are 100R and 100n as extras for same type of pedals:

 

[mosst]

I'm not too up on this stuff , but I think the 100u are smoothing caps and the 100n is there to shunt any switching noises on the circuit , I could be wrong.

 

[giovanni]

The 100R is a protection resistor I believe. If there is too much current coming from the power supply, it will likely burn. The 100n could be to filter EM interference or other higher frequency noise. It’s debatable whether you need it or not. In short, there is no single way to set up the power circuit and different design techniques or habits are used by different people.

 

[BuddytheReow]

I agree with @giovanni on this one. For power filtering there is a general rule of thumb because of the purpose of each component (resistor or capacitor), but it really boils down to the circuit designer's habits. For example the standard, and I use that term loosely, is putting a 100uf cap to ground. Sometimes you don't even need it depending on the circuit or type of power supply, but it is general good practice. Wampler talks about it in one of his books: if a schematic out there doesn't have a power filtering section (including a polarity protection diode) assume there is one of some kind. The circuit will still work without it but there may be some DC noise.