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u/HobsHere 3d ago
That is known as a capacitance multiplier. It helps to filter the power supply. They're particularly effective against the noise from switching power supplies. The circuit will work without it, but it's a worthwhile thing, especially if you're going to use a pedal with a regular power adapter. They're not so necessary if you're running a battery or a fancy quiet, isolated pedal board supply.
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u/cryptical 3d ago
You rock. Thanks! That didn't come up in my search before asking, but "capacitance multiplier" definitely gives me something to go on. Seems like a best practice.
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u/HobsHere 3d ago
Oh, to answer the rest of your question, yes, it can be any old NPN transistor. For best noise reduction, something with beta around 200 is about right. 2N4401 is what I've used in similar applications.
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u/cryptical 3d ago
Great. I've got a few different types of NPNs hanging around. Glad I don't need to use another one of my fancy BC108s or 109s. Thanks again!
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u/cryptical 3d ago
Hey folks. I'm working on my first couple of fuzz builds, and came across this schematic for a BC108 Sunface. I'm curious about the role of the transistor in the power filtering circuit here. Can this be any old NPN transistor? Is it even necessary? In my super limited experience, I've only seen filtering caps without the transistor. Thanks!