Warm Analog DSP, On The ESP

November 14, 2026 by Elliot Williams 7 Comments

We love audio, and we love messing around with it. So when [mircemk] wrote in with his latest audio-mangling device, we had to give it a look. It’s a tube-sound processor implemented in an ESP32 with a WM8960 handling the audio side of things. Tubes are expensive, power hungry, and a general pain in the posterior, so there is incentive to DIY it yourself with DSP. The whole setup is mounted in a Tektronix-inspired case that would be at home on the workbench or in the living room.

What’s ironic about the tube sound is that it’s essentially a nonlinear distortion of the audio, but it’s a distortion that can sound better than the undistorted signal. (Take that, engineering!) Push-pull transistor amplifiers tend to distort the top and bottom end of the signal similarly, while tubes round off the tops more than the bottoms. [mircemk] lets you tweak this transfer function, and displays it nicely on the screen.

But there’s one more important way that tubes color the sound — they respond slowly to rapidly changing signals — and [mircemk] says he implemented that as well. We couldn’t find that part of the distortion accounted for in the code, but maybe you can?

Anyway, this is a fantastic audio project, and it just goes to show you how far you can go with some simple parts and clever programming. Indeed, we’ve seen this rig before, with different code that made it a parametric EQ. Once you’ve got the sound turned into numbers, you can math anything at it.

Modular, 3D Printed Train Whistles For Everyone

November 11, 2026 by Tyler August 8 Comments

If the word “train” didn’t grab your attention, you’re probably not the target audience for this project. If it did, then there is no need to explain why [AeroKoi] has come up with a modular 3″ train whistle, available on Thingiverse and well explained in the video embedded below. It’s a train whistle. Who doesn’t want their own train whistle?

The great part of this design, aside from requiring less air than his earlier, larger-diameter iterations, is the modularity. With adjustable bell caps, you can alter the size of the resonant chamber and thus the notes the whistle plays on the fly. That’s the key difference between a train whistle, as used in the steam era, and a modern train horn — whistles use a resonant chamber, while a horn uses a diaphragm to create the vibrations we call sound. By using the movable chamber caps to change the resonance, you can go from a Santa Fe 5 chime to a B&O 3 chime whistle by matching the measurements in the handy-dandy spreadsheet [TrainArtisan] provided.

One excellent tip he gives in the video is to grease all the mating surfaces of the whistles with petroleum jelly, but it’s worth watching the whole thing on YouTube for both full build and tuning instructions, and to learn more than you ever thought you needed to know about whistles. He gets right into the physics of sound waves to explain exactly the limitations of trying to replicate the sound of brass steam whistles with plastic and compressed air. If you just want to hear a bunch of train whistles to see how well it works, jump to the ten minute mark. The disappointing part comes later, where he explains the airflow requirements: if you don’t have a compressor with a big tank, you can’t expect more than one short toot at a time.

Interestingly enough it looks like most of the whistles we’ve written about are locomotive-adjacent, including [AeroKoi]’s earlier work, and a true cast-brass replica for the purists.

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Web Satellite Tracker Plays The Music Of The Spheres

November 9, 2026 by Tom Nardi 4 Comments

There are a dizzying number of satellites in orbit around the Earth these days, and more are being added at an incredible rate. Those of us with an interest in space are aware of this on a conceptual level, but it’s still difficult to put into human terms. If you’re having trouble wrapping your head around the traffic buzzing overhead, perhaps the new feature on OrbitalWiki which turns satellite overflights into live music may help.

Given your location, or at least an approximation of it, OrbitalWiki can determine which of the nearly 17,000 satellites it’s currently tracking are flying over you in real-time. When each satellite hits the highest point in the sky from your perspective, it will play a single note.

The synthesized instrument and octave of each note is determined by the orbital parameters of the specific vehicle, so each one will sound slightly different. The result is a slow, sort of ambient soundscape that’s surprisingly relaxing given the “artists” are screaming around our planet at several miles per second. Since the orbits of the craft are known and predictable, you have the option of cranking up the timescale if you’d like to hear something a bit more energetic.

If you’re looking for more emergent musical content, check out [Sam Scorsby]’s fascinating project Impermanence Series A, which stitches songs together from snippets of global radio broadcasts.

PiPedal Grants Guitar Effects, Amp Emulation, And More

November 4, 2026 by Donald Papp 15 Comments

Back in the day, if one wanted a particular guitar effect one would purchase an effects pedal or “stomp box”, and even a modest collection of them could be an eye-watering investment. A guitar amp chosen for a specific sound could be another huge purchase (and who stops at one?) But if you’ve got a Raspberry Pi kicking around and a bit of free time, PiPedal provides configurable effects, guitar amp emulation, and more.

The audio engine runs on a Raspberry Pi, with configuration and control accessed by mobile device or web browser.

Things have come a long way in terms of audio processing, and PiPedal is no straightforward application of simple digital filters. We indirectly learned about it from a fellow who used it to experiment with a range of equipment he could in no reality actually afford. He shared his experience in a blog post that left him thinking he might as well sell all his pedals and build the stomp box of his dreams around PiPedal.

PiPedal’s impressive audio engine runs on a Raspberry Pi (or comparable single-board Linux computer) with control and configuration accessed from a mobile device or web browser. It’s expressly designed to seamlessly work whether one is at home, on stage, or in a studio.

The GitHub repository has code and documentation, so check it out. And if you use it as the basis of a project of your own, don’t keep it to yourself! Drop us a note on the tips line because we absolutely want to know all about it.

Beautiful Laser Harp Hides Some Neat Tricks

November 4, 2026 by Tyler August 12 Comments

Laser harps aren’t quite a right of passage, in that not everyone builds them, but it’s likely everyone at least contemplates building one at one time or another. We’re lucky that [Derrick] a.k.a. [DJ Baja Blast] didn’t stop at contemplating, and even luckier that he put together a full write-up for his tricked out laser harp — because this is a fascinating build, with features we’ve never seen in one place before.

First of all, the harp! Lasers, photodiodes, done, right? Not here! [DJ Baja Blast] kept it analog with photoresistors so that he could measure the rise and fall of the voltage as the laser light is occluded by the player’s hands — thus you can moderate the volume via faster, louder and quieter, slower plucks. More unique is the inclusion of an accelerometer. What can you do with an accelerometer in a harp? Well, here it’s being used as a tilt sensor, with the tilt acting as a control to ‘bend’ the note as it sounds, tuning it flat or sharp or altering it any other way you choose to define in software. There’s also an ultrasonic distance sensor so you can do the same thing — or any other thing, there’s no shortage of effects to chose from — theremin-style, and an encoder wheel sits on the side, so that’s five extra inputs beyond selecting a note by blocking a laser diode. Unless you count the optional looper pedal input, or the aux in.

It probably has a *teensy* learning curve, but looks like a baja blast to play.

All these inputs are driving a Teensy 4.1 microcontroller, which has the grunt for just about any synthesis or sampling, though right now [DJ Baja Blast] is sticking with the Karplus-Strong string synthesis algorithm. The Teensy can drive an onboard speaker but also offers MIDI out. Eventually he does intend to add more. Last but not least, we cannot forget that he’s plumbed this instrument to hook to a fog machine. Which makes for a visually engaging performance, and probably helps a lot when you’re learning where the laser ‘strings’ are.

The whole thing is handsomely put together with cherry and walnut. Does it sound as good as it looks? Listen to it in action in the demo video below, and judge for yourself! If you want to build your own you can grab the files on GitHub.

This is hardly the first laser harp we’ve seen, or even the first to use a Teensy, but it’s certainly got the most options to spice up a performance. It’s got to be a baja blast to play.

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The Sounds Of The World, One Random Album At A Time

October 30, 2026 by Tom Nardi 2 Comments

In the streaming era it’s easy to forget that there’s still a lot of stuff being broadcast over the radio for anyone who cares enough to dial in their receiver. Give me an antenna big enough and a tower on which to place it, and I shall listen to the world.

Of course, so you can’t actually listen to everything being blasted out all over the planet yourself. But if you’d like to at least have a little taste, check out Impermanence Series A — a project by [Sam Scorsby] that randomly combines bits and pieces of audio pulled down from shortwave and FM broadcasts with some web streams, live microphones, and even a bit of the Internet Archive each day into a one of a kind album. We’re not sure we’d call it music, exactly. But it’s certainly fascinating to listen to, a bit like randomly spinning the dial on a planet-wide radio receiver.

[Sam] has shared the Python scripts that pull together each day’s album, and he’s not shy about the fact that the project was created with the help of artificial intelligence tools. In fact, that’s sort of the point. [Sam] puts himself somewhere in the middle when it comes to the current debate over AI, and acknowledges that while computers are good at processing raw data, it still takes a human touch to put it all into context.

So each day [Sam] will listen to the latest computer-generated album and pick his favorite tracks, and once the project has run its course, he’ll put together a human-curated “Best Of” collection. Man and machine working together, each doing what they do best.

We know something of opinionated folks on the Internet, and our experience tells us that Impermanence Series A is unlikely to change anyone’s minds when it comes to AI. But we do appreciate the thoughtful approach [Sam] has taken with the project, and look forward to hearing what he comes up with in the end.

Using An Unmodded GBA As A Music Synth

October 23, 2026 by Bryan Cockfield 5 Comments

The style and sound of older video games is unique enough that they’re still copied in relatively modern games like Undertale, Celeste, or Shovel Knight. There’s also a vibrant chiptune community making music on the older hardware directly. Often this involves hardware modding or otherwise finding chips from older gaming systems to replicate that unique retro gaming sound authentically. But disassembling older systems is not always necessary. Take a look at this Game Boy Advance synthesizer which uses the GBA hardware with no modifications at all.

The key to making this work is the GBA’s multiboot feature, which allowed these systems to send executable code over a link cable to other consoles which didn’t have cartridges. This meant that friends could play multiplayer games without each one needing their own cartridge, but it also means that nowadays people can send their own custom software directly to the console’s RAM without much extra effort. To run the synthesizer software, the GBA is connected to a computer, the software is started, and then when the GBA is powered on the snythesizer is automatically loaded into its RAM. The audio output is played over the headphone jack, and various controls are available on the computer and on the console.

In the video linked below, [Andy] is using the GBA with some other musical hardware and the sounds he’s getting from the unmodified console are impressive. It could certainly be a go-to for anyone interested in getting started in this style of music or who doesn’t want to do something like take apart an original Sega Genesis for the audio circuitry.

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