The guitarist Jimi Hendrix had a unique sound which has influenced countless musicians over the decades. He achieved it through mastery not only of his instrument, but of the complex feedback relationship between amplifier, environment, and guitar — coupled with a series of effects pedals including some then-unique ones made for him. Musical commentators have pored over his work for decades, but a recent piece in IEEE Spectrum is particularly interesting as it examines things from a technical perspective.
It centers around an electrical simulation of Hendrix’s effects chain, and makes an assertion that’s obvious on consideration but not the usual take on a Hendrix performance; that in his hands it became a wave synthesizer rather than the instrument itself. Certainly for anyone with an interest in analogue audio electronics as they pertain to musical synthesis it helps in placing the influence of the different circuits on the sound, and in hearing the familiar performances in a new light.
This isn’t the first time we’ve seen someone take a modelling approach to a guitar effects chain, indeed it’s obvious something missing from the work above is the guitar itself.
Header image: Gemeente Rotterdam (Stadsarchief) CC-0.
We’ve all built projects that are a rats’ nest of wiring and feature creep, but the best projects in the end are usually those that use a simple solution to elegantly solve a problem. [Kauz] had been thinking about a unique type of electric guitar pickup for a while and rather than purchase an expensive option or build a complex microcontroller-based system he found his elegant solution in the form of a common electronic component.
The core of this idea is that guitar pickups are essentially coils of wire, and are surprisingly similar to the coils of wire found in electromechanical relays. [Kauz] has used six small relays, left them unmodified, and then built an amplifier circuit for each to allow the vibrations of the guitar strings to resonate in the relay coils, eventually producing a sound. Not only do the relays work perfectly well as pickups, but [Kauz] also created a mixing board that allows the six relays to be combined into two channels, allowing for options like stereo sound for different strings directly out of the guitar or for different effects to be applied to different strings.
The build also allows for some interesting options in future versions as well. [Kauz]’s plans are eventually to build this into an instrument which can output polyphonic MIDI signals, where various strings can behave as different instruments. In theory, with six circuits six different instruments can be produced, and we’re excited to see what the next versions will look and sound like. In the meantime, be sure to check out some other guitar pickups we’ve seen that use even simpler parts found lying around the workbench.
We wrote recently about a maker’s quest to create just such a hybrid instrument, and why it ended in failure: pressing strings onto the fretboard also pushed them tighter to the wheel, ruining the all-important tension. To recap, the spinning wheel of a hurdy-gurdy excites the strings exactly like a violin bow, and like a violin bow, the pressure has to be just right. There’s no evidence [Keizo Ishibashi] was aware of that work, but he solved the problem regardless, simply by thinking outside the box — the soundbox, that is.
Unlike a hurdy-gurdy, the Cantareel keeps its wheel outside the soundbox. The wheel also does not rub directly upon the strings: instead, it turns what appears to be a pair of o-rings. Each rosined o-ring bows 2 of the guitar’s strings, giving four strings a’ singing. (Five golden rings can only be assumed.) The outer two strings of this ex-six-string are used to hold the wheel assembly in place by feeding through holes on the mounting arms. The guitar is otherwise unmodified, making this hack reversible.
It differs from the classic hurdy-gurdy in one particular: on the Cantareel, every string is a drone string. There’s no way to keep the rubber rings from rubbing against the strings, so all four are always singing. This may just be the price you pay to get that smooth gurdy sound out of a guitar form factor. We’re not even sure it’s right to call it a price when it sounds this good.
If you’re looking for a long journey into the wonderful world of instrument hacking, [Arty Farty Guitars] is six parts into a seven part series onhacking an existing guitar into a guitar-hurdy-gurdy-hybrid,and it is “a trip” as the youths once said. The first video is embedded below.
The Hurdy-Gurdy is a wheeled instrument from medieval europe, which you may have heard of, given the existence of the laser-cut nerdy-gurdy, the electronicmidi-gurdy we covered here, and the digi-gurdy whichseems to be a hybrid of the two. In case you haven’t seen one before, the general format is for a hurdy-gurdy is this : a wheel rubs against the strings, causing them to vibrate via sliding friction, providing a sound not entirely unlike an upset violin. A keyboard on the neck of the instrument provides both fretting and press the strings onto the wheel to create sound.
[Arty Farty Guitars] is a guitar guy, so he didn’t like the part with about the keyboard. He wanted to have a Hurdy Gurdy with a guitar fretboard. It turns out that that is a lot easier said than done, even when starting with an existing guitar instead of from scratch, and [Arty Farty Guitar] takes us through all of the challenges, failures and injuries incurred along the way.
Probably the most interesting piece of the puzzle is the the cranking/keying assembly that allows one hand to control cranking the wheel AND act as keyboard for pressing strings into the wheel. It’s key to the whole build, as combining those functions on the lower hand leaves the other hand free to use the guitar fretboard half of the instrument. That controller gets its day invideo five of the series. It might inspire some to start thinking about chorded computer inputs– scrolling and typing?
If you watch up to the sixth video, you learn that that the guitar’s fretting action is ultimately incompatible with pressing strings against the wheel at the precise, constant tension needed for good sound. To salvage the project he had to switch from a bowing action with a TPU-surfaced wheel to a sort of plectrum wheel, creating an instrument similar to thethousand-pick guitar we saw last year.
Even though [Arty Farty Guitars] isn’t sure this hybrid instrument can really be called a Hurdy Gurdy anymore, now that it isn’t using a bowing action, we can’t help but admire the hacking spirit that set him on this journey. We look forward to the promised concert in the upcoming 7th video, once he figures out how to play this thing nicely.
The build is based around a central core, which combines the pickups, bridge, and neck into one solid unit. This is really the heart of the guitar, containing all the pieces that need to be in precise alignment to get those strings vibrating precisely in tune. The core then mounts to a printed outer body via mating slots and rails, which in the main demo is made to look like a Les Paul-style design. This outer body also hosts the volume, tone, and pickup controls. Output from the pickups travels to the controls in the outer body via a set of metallic contacts.
What’s cool about this build is that the sky really is the limit for your creativity. As the video below demonstrates, the main build looks like a Les Paul. But, armed with the right CAD software, you can really make a guitar that looks like whatever you want, while the 3D printer does all the hard work of making it a reality. The files to print the guitar, along with the pickups and other components, are available as kits—but there’s also nothing stopping you from working up your own printed guitar design from scratch, either.
For better or worse, the fundamental design of guitars has remained familiar since they electrified around a century ago. A few strings, a fretboard, and a body of some sort will get you most of the way there for an acoustic guitar, with the addition of electromagnetic pickups and wiring for electric variants. However, technology has advanced rapidly in the last 100 years outside the musical world, so if you want to see what possibilities lie ahead for modernizing guitars take a look at the Cyberbass created by [Matteo].
The guitar starts its life as many guitars do: with a block of wood. One of the design goals was to be able to use simple tools to build the guitar, so the shape of the instrument was honed with a Japanese hacksaw and the locations for the pickups and other electronics were carved out with chisels.
The neck of the guitar was outsourced since they take some pretty specialized tools to build, so simply bolting it to the body takes care of that part of the build, but [Matteo] had a few false starts setting the bridge in the exact location it needed to be.
Luckily he was able to repair the body and move the bridge. With the core of the guitar ready, it was on to paint and then to its custom electronics. [Matteo] built in not only a set of pickups and other common electric guitar parts but also integrated a synth pedal into the body as well as including a chromatic tuner.
With everything assembled and a few finishing touches added including a custom-engraved metal signature plate, the Cyberbass is ready to go on tour. [Matteo] learned a lot about guitar building in general, as well as a few things about electronics relating to musical instruments (including how expensive tuners work just as well as cheap ones).
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.
