The Reverse Oscilloscope

September 25, 2023 by Al Williams 17 Comments

Usually, an oscilloscope lets you visualize what a signal looks like. [Mitxela]’s reverse oscilloscope lets you set what you want an audio waveform to look like, and it will produce it. You can see the box in the video below.

According to [Mitxela] part of the difficulty in building something like this is making the controls manageable for mere mortals. We really like the slider approach, which seems pretty obvious, but some other controls are a bit more subtle. For example, the interpolation control can create a squarish wave or a smooth waveform, or anything in between.

This is sort of an artistic take on an arbitrary waveform generator but with a discrete-panel user interface. The device contains a Teensy, a Raspberry PI Pico, a 16-bit ADC, and an external DAC. The Pico is little more than an I/O controller, reading the user interface and transmitting it on a serial port.

The outside construction looks excellent (we assume the tape is temporary). The inside is a bit messier, but still nicely done. There are many photos of the construction and details of problems along the way with 12-bit ADCs and power supply experiments.

Of course, if you don’t need the user interface, you can go crazy with waveform generation. We did our own similar project, but you could draw your waveforms on the PC instead of sliders.

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A rotary subwoofer made out of a speaker coil, a medium-size fan an a grey wooden box to stand on.

Tear Apart Your House For $200 With This Rotary Subwoofer

September 8, 2023 by Julian Scheffers 44 Comments

Many movies and songs use a lot of of bass to make it feel more real to the viewer or listener. Because of this, subwoofers are common in high-quality audio setups, often costing a substantial part of the budget. [Daniel Fajkis] takes the subwoofer to it’s logical extreme by building a rotary subwoofer on a $200 budget.

The principle of a rotary subwoofer is that a normal subwoofer physically moves the air, and so does a fan. If you could make a fan oscillate the air instead of only pushing it, you could turn it into such a subwoofer, which is exactly what [Daniel] did. [Daniel] mounts a large electric motor on the case of an ex-subwoofer to spin the fan. Then, he uses the rotor linkage of a model helicopter and a modified subwoofer speaker to pitch the fan blades, spinning around to create a truly impressive gust of air oscillating at as low as 1 Hz.

The video, after the break, is well made with some good humor, including the legendary quote: “It’s gonna tear apart my household, there’s no way we’re surviving this one.”
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Where Did Electronic Music Start?

September 7, 2023 by Jenny List 53 Comments

A culture in which it’s fair to say the community which Hackaday serves is steeped in, is electronic music. Within these pages you’ll find plenty of synthesisers, chiptune players, and other projects devoted to synthetic sound. Not everyone here is a musician of obsessive listener, but if Hackaday had a soundtrack album we’re guessing it would be electronic. Along the way, many of us have picked up an appreciation for the history of electronic music, whether it’s EDM from the 1990s, 8-bit SID chiptunes, or further back to figures such as Wendy Carlos, Gershon Kingsley, or Delia Derbyshire. But for all that, the origin of electronic music is frustratingly difficult to pin down. Is it characterised by the instruments alone, or does it have something more specific in the music itself? Here follows the result of a few months’ idle self-enlightenment as we try to get tot he bottom of it all.

Will The Real Electronic Music Please Stand Up?

Page from the Telharmonium patent, showing the tone wheels — If you own a synthesiser, the Telharmonium is its daddy.

Anyone reading around the subject soon discovers that there are several different facets to synthesised music which are collectively brought together under the same banner and which at times are all claimed individually to be the purest form of the art. Further to that it rapidly becomes obvious when studying the origins of the technology, that purely electronic and electromechanical music are also two sides of the same coin. Is music electronic when it uses an electronic instrument, when electronics are used to modify the sound of an acoustic instrument, when it is sequenced electronically often in a manner unplayable by a human, or when it uses sampled sounds? Is an electric guitar making electronic music when played through an effects pedal?

The history of electronic music as far as it seems from here, starts around the turn of the twentieth century, and though the work of many different engineers and musicians could be cited at its source there are three inventions which stand out. Thaddeus Cahill’s tone-wheel-based Telharmonium US patent was granted in 1897, the same year as that for Edwin S. Votey’s Pianola player piano, while the Russian Lev Termen’s Theremin was invented in 1919. In those three inventions we find the progenital ancestors of all synthesisers, sequencers, and purely electronic instruments. If it appears we’ve made a glaring omission by not mentioning inventions such as the phonograph, it’s because they were invented not to make music but to record it. Continue reading “Where Did Electronic Music Start?” →

Spooky Noise Box Has Post-Halloween Potential

September 5, 2023 by Kristina Panos 8 Comments

There’s more than one way to scare people on Halloween. Sure, there’s always the low-brow jump scare, but that will generally just annoy the person and possibly cause a heart attack. No, what you need is a sustained soundscape of hellish audio. And where does one find hellish audio? Well, you make your own with a spooky-sounds noise box.

And no, we’re not talking about a soundboard that goes ‘boo’ and ‘ooo-OOO-oooh’ and whatnot. This is a full-on DIY instrument that has potential beyond Halloween. Essentially, the wooden box takes input vibrations from various doodads, and these vibrations are picked up by a piezo disk or two glued to the underside of the lid. The piezos are wired up to a 3.5 mm jack, which runs out to the PC and [SvartalfarQc]’s favorite Digital Audio Workstation (DAW). From there, it’s just a matter of playing around with the sounds — looping them, running them through various instrument voices, adding effects, and so on.

We love the the things that [SvartalfarQc] came up with, including a wind-up walking heart thing, a retractable badge holder, and that noise box mainstay, a sproingy doorstop.

We all know piezos are awesome, but have you ever considered that they can be used to digitize old wax cylinder recordings?

Re-Creating Pink Floyd In The Name Of Speech

September 1, 2023 by Kristina Panos 18 Comments

For people who have lost the ability to speak, the future may include brain implants that bring that ability back. But could these brain implants also allow them to sing? Researchers believe that, all in all, it’s just another brick in the wall.

In a new study published in PLOS Biology, twenty-nine people who were already being monitored for epileptic seizures participated via a postage stamp-sized array of electrodes implanted directly on the surface of their brains. As the participants were exposed to Pink Floyd’s Another Brick In the Wall, Part 1, the researchers gathered data from several areas of the brain, each attuned to a different musical element such as harmony, rhythm, and so on. Then the researchers used machine learning to reconstruct the audio heard by the participants using their brainwaves.

First, an AI model looked at the data generated from the brains’ responses to components of the song, like the changes in rhythm, pitch, and tone. Then a second model rejiggered the piecemeal song and estimated the sounds heard by the patients. Of the seven audio samples published in the study results, we think #3 sounds the most like the song. It’s kind of creepy but ultimately very cool. What do you think?

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Guitar Distortion With Diodes In Code, Not Hardware

August 23, 2023 by Dan Maloney 14 Comments

Guitarists will do just about anything to get just the right sound out of their setup, including purposely introducing all manner of distortion into the signal. It seems counter-intuitive, but it works, at least when it’s done right. But what exactly is going on with the signal? And is there a way to simulate it? Of course there is, and all it takes is a little math and some Arduino code.

Now, there are a lot of different techniques for modifying the signal from an electric guitar, but perhaps the simplest is the humble diode clipping circuit. It just uses an op-amp with antiparallel diodes either in series in the feedback loop or shunting the output to ground. The diodes clip the tops and bottoms off of the sine waves, turning them into something closer to a square wave, adding those extra harmonics that really fatten the sound. It’s a simple hack that’s easy to implement in hardware, enough so that distortion pedals galore are commercially available.

In the video below, [Sebastian] explains that this distortion is also pretty easy to reproduce algorithmically. He breaks down the math behind this, which is actually pretty approachable — a step function with a linear part, a quadratic section, and a hard-clipping function. He also derives a second, natural exponent step function from the Schockley diode equation that is less computationally demanding. To implement these models, [Sebastian] chose an Arduino GIGA R1 WiFi, using an ADC to digitize the guitar signal and devoting a DAC to each of the two algorithms. Each distortion effect has its own charms; we prefer the harsher step function over the exponential algorithm, but different strokes.

Kudos to [Sebastian] for this easy-to-understand treatment of what could otherwise be a difficult subject to digest. We didn’t really expect that a guitar distortion pedal would lead down the rabbit hole to diode theory and digital signal processing, but we’re glad it did.

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An Effects Pedal For Keyboards (and Mice)

August 21, 2023 by Bryan Cockfield 4 Comments

Effects pedals for musical instruments like electric guitars can really expand a musician’s range with the instrument. Adding things like distortion, echo, and reverb at the push of a button can really transform the sound of a guitar and add depth to a performance. But [Guy] wondered why these effects should be limited to analog signals such as those from musical instruments, and set about to apply a number of effects to the use of computer keyboards and mice with this HID effects pedal.

The mouse is perhaps the closer of the two to an analog device, so the translations from the effects pedal are somewhat intuitive. Reverb causes movements in the mouse to take a little bit of extra time before coming to a stop, which gives it the effect of “coasting”. Distortion can add randomness to the overall mouse movements, but it can also be turned down and even reversed, acting instead as a noise filter and smoothing out mouse movements. There’s also a looper, which can replay mouse movements indefinitely and a crossover, which allows the mouse to act as a keyboard.

For the keyboard, included effects are a tremolo, which modulates between upper- and lower-case at certain intervals; echo, which repeats keypresses; and a pitch-shift which outputs a “higher” character in the alphabet above whichever one has been pressed. Like the mouse, there’s also a crossover mode which allows the keyboard to be used as a mouse.

The device looks and feels like an effects pedal for a guitar would, with a RP2040 inside to intercept HID information, do the signal processing, and then output the result to the computer. And, while [Guy] admits this was a fun project with not many practical uses, there are a couple handy ones including potentially the distortion effect to smooth out mouse inputs for those with neuromuscular disorders or the mouse looper to act as a mouse jiggler for those with micromanaging employers. It’s also reprogrammable, and as we’ve seen since time immemorial having a programmable foot keyboard can be extremely handy for certain workflows.

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