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Most of my building (at least up until a few years ago) was either scratch builds or mods for home audio equipment. One of the first mods typically made, even to "high end" gear, was upping the filter capacitors, and making sure everything had good bypass caps on it. Several things to note though—these were all supplies that were converting AC to DC, and the goal was as much fidelity as possible. (Neither really apply to the vast majority of guitar effects.) But, I used to almost always up the supply caps to several hundred uF, and usually had on or two bypass caps on them, usually a polypropylene in the nano range, and a styrene in the upper pico range. This is all overkill for pedals, but I still (when the schematic doesn't call for it) fit in a 100nF box cap, either right at the main supply cap, or right at the ICs—very little extra work or cost, and it does give you benefits (speed and some filtering advantages—I think?—). The larger supply caps make for a "stiffer" supply, so in pedals that go for sag, etc., it's actually a detriment. Less "amp feel" when you're playing.I have been thinking about the power section for a while now. Mainly because I see so many variations in the power sections and I am trying to design a pedal and want to try to make it so that you could have a noisy power supply and the pedal would filter out the noise.
I have a few questions.
1. On the Mach1 schematic, they use a 20uf capacitor. If you increase it to 100uf, will this improve filtering and will it change anything about the sound of the pedal?
2. I was reading an article from Coda Effects about capacitors and they recommend an electrolytic cap and film cap in parallel for better filtration. Ideally, should you always do this?
Coda Effects: All you need to know about capacitors in guitar pedals
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The short answer, in my self taught experience, is no. There is no magic formula. “Standard” filtering that I’ve seen in schematics is 47uf or 100uf electro caps. Sometimes you’ll notice on the breadboard a sweet spot for how much DC filtering should be done. Sometimes you just need 22uf or as much as 100uf+. You’ll just need to experiment. It also depends on how good your power supply is too.
Thanks. I've been trying to research this subject for a while, but I haven't really found anything concrete. In my studio, I have LED lights that generate some noise. It isn't really noticeable through the mixing console, but I do notice it in some of my pedals, and I think my guitar cables pick it up a little too. I know it's coming from the LEDs because when I turn off the lights, it goes away, but it's really hard to work in the dark, so I'm trying to find a filtering solution.
Thanks, you've cleared up something that piqued my curiosity awhile back: exactly why various 9V power supplies use varying R and C values.
I stand corrected. Clearly I'm not the expert here...
This is awesome. This low-pass filter calculator is going to come in very handy.
This makes so much sense. I just never though about the power filtering as a low-pass filter.
The relevance of 2 capacitors, #1 a larger electrolytic + #2 a smaller film cap is the following:
