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Question regarding 9V power supply filtering. I built a couple of treble boosters over the past year using the GBOF board and when built I used a 9V Battery to test the pedals with the usual setup: Guitar>Pedal>Amp and everything sounded fine. I went to use a 9V Power Supply (One Spot) instead of a battery and just got horrible background noise from the pedal. Replacing the One Spot with a battery resolved the issue.
Since I have no power supply filtering built into the circuitry, I was wondering if a simple add-on from the power jack would resolve the issue with the One Spot. However, I am not sure what configuration and values would work between the power jack and power input to the board.
Example 1 is from the GPCB One Knob fuzz circuit
Example 2 is another configuration.
And Example 3 is a third type.
Which circuit would be the best for my situation and what are the recommended Diodes and Capacitor Values?
All of the above designs work to some extent. By that I mean it depends on how much noise is present in the AC source and how much is generated by the power supply itself.
You may find that a single stage of filtering will suffice in some situations while severe noise environments will require multiple stages of filtering. I have used an O’scope to examine noise in a power supply. As I added additional filter capacitors of various values, the noise continued to be reduced to a point.
I hope this helps.
For further clarification, we are discussing the remaining ripple noise that is left by the power supply. The power supply itself has its own filter capacitor(s). I investigated and found that there are formulas to determine the correct value for the filter (smoothing) capacitor in a DC power supply. But, we are discussing how to manage the ripple noise that is found after the DC voltage leaves the power supply and enters our pedals.
I found that adding additional stages of filer capacitors in pedal circuits can further reduce the audible noise found in the supply. One source stated that increasing the filer capacitors by a factor of 10 would reduce the ripple noise by the same factor.
I hope this helps.
Thanks Wilkie. I had also done some reading along this line and some of it was beyond my limited electronics knowledge to completely understand how to figure things out. I just started looking at some of the available schematics for various treble boosters and found that the most common filtering is a series Shottky diode for reverse polarity protection with a 47uf capacitor to ground for noise filtering. So some people have already done the work for me I guess and that’s what I will try, at least at first. Similar to the One Knob Fuzz schematic but with a larger capacitor.
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