Duocast R13 use?

[Dan0h]

Still trying to learn more so I don’t have to ask these noob questions.
What does R13 (10ohms) do in the Duocast build? I see it’s coming off the voltage switch from the charge pump, but what is its purpose. And specifically my 10ohm resisters were all reading closer to 15ohms how will this affect the circuit. Am I ok, will it sound different?
Much appreciated, thanks.

 

[Nostradoomus]

That and the 120uf cap to ground after it form an RC low pass filter to get rid of unwanted power supply noise. Going up to 15ohms won’t hurt anything at all, it’s not in the actual audio path.

 

[Dan0h]

I found this RC Low Pass calculator. Not sure how accurate it is but according to this the change from 10ohm resistor and 120uf cap to 15 ohm and 100uf changes the cut off Freq from around 132Hz to around 106hz.

Another noob question, since this is on the power section of the circuit how does the frequency affect the power? And does power only affect how the components react or is there a relation to the audio. Have a pretty solid grasp on audio frequency but power is a new realm for me.

Low Pass Filter Calculator

1st order and 2nd order low pass filter ✓ Low pass filter calculator ✓ Low pass filter circuit ✓ Cutoff frequency low pass filter Calculator ✓ RC vs RL vs LC low pass filter ✓

electronicbase.net

 

[Chuck D. Bones]

That 120uF cap is not critical, many people use 100uF because they're easier to find. 150uF and 220uF are also acceptable, as long as they will fit.

Power supplies would make for a great topic in Chucks Boneyard. I'll give you a short answer here: the cleaner the power, the better. A battery is a very clean source of DC power, which is why most of the early pedals did not have or need filter capacitors. The power supply filter caps reduce the ripple and noise coming in from the external power supply. The external power supplies have their own filtering, but it may not be enough. The filter caps also keep the various parts of the circuit from interfering with each other thru the power supply rail (people who build tube amps know all about that!). The series resistor helps the capacitors perform filtering, but at a cost: there is voltage drop in the resistor. More resistance gives better filtering, but if the resistor is too big, then there is not enough voltage left to run the circuit.

 

[Dan0h]

That 120uF cap is not critical, many people use 100uF because they're easier to find. 150uF and 220uF are also acceptable, as long as they will fit.

Power supplies would make for a great topic in Chucks Boneyard. I'll give you a short answer here: the cleaner the power, the better. A battery is a very clean source of DC power, which is why most of the early pedals did not have or need filter capacitors. The power supply filter caps reduce the ripple and noise coming in from the external power supply. The external power supplies have their own filtering, but it may not be enough. The filter caps also keep the various parts of the circuit from interfering with each other thru the power supply rail (people who build tube amps know all about that!). The series resistor helps the capacitors perform filtering, but at a cost: there is voltage drop in the resistor. More resistance gives better filtering, but if the resistor is too big, then there is not enough voltage left to run the circuit.

Thanks Chuck, I appreciate the knowledge.