Homebrew Foil And Oil Caps Change Your Guitar’s Tone

February 4, 2025 by Dan Maloney 47 Comments

How any string instrument sounds depends on hundreds of factors; even the tiniest details matter. Seemingly inconsequential things like whether the tree that the wood came from grew on the north slope or south slope of a particular valley make a difference, at least to the trained ear. Add electronics into the mix, as with electric guitars, and that’s a whole other level of choices that directly influence the sound.

To experiment with that, [Mark Gutierrez] tried rolling some home-brew capacitors for his electric guitar. The cap in question is part of the guitar’s tone circuit, which along with a potentiometer forms a variable low-pass filter. A rich folklore has developed over the years around these circuits and the best way to implement them, and there are any number of commercially available capacitors with the appropriate mojo you can use, for a price.

[Mark]’s take on the tone cap is made with two narrow strips of regular aluminum foil separated by two wider strips of tissue paper, the kind that finds its way into shirt boxes at Christmas. Each of the foil strips gets wrapped around and crimped to a wire lead before the paper is sandwiched between. The whole thing is rolled up into a loose cylinder and soaked in mineral oil, which serves as a dielectric.

To hold the oily jelly roll together, [Mark] tried both and outer skin of heat-shrink tubing with the ends sealed by hot glue, and a 3D printed cylinder. He also experimented with a wax coating to keep the oily bits contained. The video below shows the build process as well as tests of the homebrew cap against a $28 commercial equivalent. There’s a clear difference in tone compared to switching the cap out of the circuit, as well as an audible difference in tone between the two caps. We’ll leave the discussion of which sounds better to those with more qualified ears; fools rush in, after all.

Whatever you think of the sound, it’s pretty cool that you can make working capacitors so easily. Just remember to mark the outer foil lead, lest you spoil everything.

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Just What Is Tone, In A Microphone?

October 5, 2023 by Jenny List 23 Comments

As long-time Hackaday readers will know, there is much rubbish spouted in the world of audio about perceived tone and performance of different hi-fi components. Usually this comes from audiophiles with, we’d dare to suggest, more money than sense. But oddly there’s an arena in which the elusive tone has less of the rubbish about it and it in fact, quite important. [Jim Lill] is a musician, and like all musicians he knows that different combinations of microphones impart a different sound to the recording. But as it’s such a difficult property to quantify, he’s set out to learn all he can about where the tone comes from in a microphone.

He’s coming to this from the viewpoint of a musician rather than an engineer, but his methodology is not diminished by this. He’s putting each mic on test in front of the same speaker at the same position, and playing a standard piece of music and a tone sweep through each. He doesn’t have an audio analyser, reference speaker and microphone, or anechoic chamber, so he’s come up with a real-world standard instead. He’s comparing every mic he can find with a Shure SM57, the go-to general purpose standard in the world of microphones for as long as anyone can remember, being a 1960s development of their earlier Unidyne series. His reasoning is that while its response is not flat the sound of the SM57 is what most people are used to hearing from a microphone, so it makes sense to measure the others against its performance.

Along the way he tests a huge number of microphones including famous and expensive ones from exclusive studios and finally one he made himself by mounting a cartridge atop a soda can. You’ll have to watch the video below the break for his conclusions, we can promise it’s worth it.

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Axe Hacks: Spinning Knobs And Flipping Switches

October 15, 2020 by Sven Gregori 15 Comments

From a guitar hacking point of view, the two major parts that are interesting to us are the pickups and the volume/tone control circuit that lets you adjust the sound while playing. Today, I’ll get into the latter part and take a close look at the components involved — potentiometers, switches, and a few other passive components — and show how they function, what alternative options we have, and how we can re-purpose them altogether.