digital audio hacks

729 Articles

DIY MP3 Player Inspired By The IPod

August 1, 2025 by 5 Comments

These days, the personal MP3 player has been largely replaced by the the smartphone. However, [Justinas Petkauskas] still appreciates the iPod for its tactility and portability, and wanted to bring that vibe back. Enter JPL.mp3

The build is based around the ESP32-S3 microcontroller. It’s hooked up with a PCM5102 DAC hooked up over I2S to provide quality audio, along with a micro SD card interface for music storage, and a small IPS LCD. The best feature, though? The mechanical click-wheel which provides a very tactile way to scroll and interact with the user interface. Everything is assembled into a neat 3D printed case, with a custom four-layer PCB lacing all the electronics together.

On the software side, [Justinas] cooked up some custom software for organizing music on the device using a SQLite database. As he primarily listens to classical music, the software features fields for composer/piece and conductor, orchestra, or performer.

[Justinas] calls the final build “chunky, but nevertheless functional” and notes it is “vaguely reminiscent of classic iPods.” We can definitely see the fun in building your own personalized version of a much-enjoyed commercial product, for sure. Meanwhile, if you’re cooking up your own similar hardware, we’d certainly love to hear about it.

A rough, pixelated outline of a bird is shown in white in the top of the image. A red replica of this image is shown in a spectrogram in the lower half of the image. A smaller picture-in-picture display in the bottom right of the image shows a man sitting in a studio.

AVIF: The Avian Image Format

July 29, 2025 by 35 Comments

Humans have long admired the sound of birdsong, but to fully appreciate how technically amazing it is, you need an ultrasonic microphone. [Benn Jordan] recently created a video about using these microphones to analyze a collection of bird calls, even training a starling to repeat an image encoded in sound, and has some recommendations for amateurs wanting to get started in computational ornithology.

In the first part of the video, [Benn] set up automated ultrasonic recorders at home, made recordings in Florida and rural Georgia, and visited a starling named “The Mouth,” famous for his ability to mimic human sounds. As a demonstration of his abilities, [Benn] drew a simple bird shape in a spectrogram, converted it into sound, and played it for The Mouth several times. Initially, it didn’t seem that the starling would repeat it, but while he was analyzing his recordings later, [Benn] found the characteristic bird shape. The Mouth had been able to repeat it almost pitch-perfectly. It was in this analysis that the ultrasonic microphones showed their worth, since they were able to slow down the birds’ complex vocalizations enough to detect their complex structures without losing audio quality. Continue reading “AVIF: The Avian Image Format” →

Teufel Introduces An Open Source Bluetooth Speaker

July 24, 2025 by 33 Comments

There are a ton of Bluetooth speakers on the market. Just about none of them have any user-serviceable components or replacement parts available. When they break, they’re dead and gone, and you buy a new one. [Jonathan Mueller-Boruttau] wrote in to tell us about the latest speaker from Teufel Audio, which aims to break this cycle. It’s a commercial product, but the design files have also been open sourced — giving the community the tools to work with and maintain the hardware themselves.

The project is explained by [Jonathan] and [Erik] of Teufel, who were part of the team behind the development of the MYND speaker. The basic idea was to enable end-user maintenance, because the longer something is functioning and usable, the lower its effective environmental footprint is. “That was why it was very important for us that the MYND be very easy to repair,” Erik explains. “Even users without specialist knowledge can replace the battery no problem.” Thus, when a battery dies, the speaker can live on—versus a regular speaker, where the case, speakers, and electronics would all be thrown in the garbage because of a single dead battery. The case was designed to be easy to open with minimal use of adhesives, while electronic components used inside are all readily available commercial parts.

Indeed, you can even make your own MYND if you’re so inclined. Firmware and hardware design files are available on GitHub under the Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license for those looking to repair their speakers, or replicate them from the ground up. The company developed its own speaker drivers, but there’s nothing stopping you from using off-the-shelf replacements if so desired.

It’s a strategy we expect few other manufacturers to emulate. Overall, as hackers, it’s easy to appreciate a company making a device that’s easy to repair, rather than one that’s designed to frustrate all attempts made. As our own Jenny List proclaimed in 2021—”You own it, you should be able to fix it!” Sage words, then as now!

Volume Controller Rejects Skeumorphism, Embraces The Physical

July 9, 2025 by 34 Comments

The volume slider on our virtual desktops is a skeuomorphic callback to the volume sliders on professional audio equipment on actual, physical desktops. [Maker Vibe] decided that this skeuomorphism was so last century, and made himself a physical audio control box for his PC.

Since he has three audio outputs he needs to consider, the peripheral he creates could conceivably be called a fader. It certainly has that look, anyway: each output is controlled by a volume slider — connected to a linear potentiometer — and a mute button. Seeing a linear potentiometer used for volume control threw us for a second, until we remembered this was for the computer’s volume control, not an actual volume control circuit. The computer’s volume slider already does the logarithmic conversion. A Seeed Studio Xiao ESP32S3 lives at the heart of this thing, emulating a Bluetooth gamepad using a library by LemmingDev. A trio of LEDs round out the electronics to provide an indicator for which audio channels are muted or active.

Those Bluetooth signals are interpreted by a Python script feeding a software called Voicmeeter Banana, because [Maker Vibe] uses Windows, and Redmond’s finest operating system doesn’t expose audio controls in an easily-accessible way. Voicmeeter Banana (and its attendant Python script) takes care of telling Windows what to do. 

The whole setup lives on [Maker Vibe]’s desk in a handsome 3D printed box. He used a Circuit vinyl cutter to cut out masks so he could airbrush different colours onto the print after sanding down the layer lines. That’s another one for the archive of how to make front panels.

If volume sliders aren’t doing it for you, perhaps you’d prefer to control your audio with a conductor’s baton. 

Continue reading “Volume Controller Rejects Skeumorphism, Embraces The Physical” →

Pi Pico Powers Parts-Bin Audio Interface

June 20, 2025 by 10 Comments

USB audio is great, but what if you needed to use it and had no budget? Well, depending on the contents of your parts bin, you might be able to use [Veyniac]’s Pico-Audio-Interface as a free (and libre! It’s GPL3.0) sound capture device.

In the project’s Reddit thread, [Veyniac] describes needing audio input for his homemade synth, but having no budget. Necessity being the mother of invention, rather than beg borrow or steal a device with a working sound card, he hacked together this lovely device. It shows up as a USB Audio Class 2.0 device so should work with just about anything, and offers 12-bit resolution and 4x oversampling to try and deal with USB noise with its 2-channel, 44.1 kHz sample rate.

Aside from the Pico, all you need is an LM324 op-amp IC and a handful of resistors and capacitors — [Veyniac] estimates about $10 to purchase the whole BOM. He claims that the captured audio sounds okay in his use, but can’t guarantee it will  be for anyone else, noise being the fickle beast that it is. We figure that sounding “Okay” has got to be pretty good, given that you usually get what you pay for — and again, [Veyniac] did build this in a cave with a box of scraps. Well, except for the cave part. Probably.

While the goal here was not to rival a commercial USB sound card, we have seen projects to do that. We’re quite grateful to [Omadeira] for the tip, because this really is a hack. If you, too, want a share of our undying gratitude (which is still worth its weight in gold, despite fluctuations in the spot price of precious metals), send in a tip of your own.

Hand holding small speaker

Ben Eater Makes Computer Noises

June 19, 2025 by 7 Comments

When [Ben Eater] talks, hackers everywhere listen. In his latest video [Ben] shows us how to make computer noises using square waves and a 6502 microprocessor.

[Ben] uses the timer in the W65C22 Versatile Interface Adapter to generate the square waves which generate a tone. He then adds support for a new BEEP command into his MS BASIC interpreter. We covered [Ben Eater]’s MS BASIC here at Hackaday back in April, so definitely check that out if you missed it.

Continue reading “Ben Eater Makes Computer Noises” →

A black PCB is shown, with an Arduino Nano mounted in the bottom left corner. The rest of the space on the PCB is used up by ten DIP integrated circuits and a few resistors and diodes. Several black and red wires connect different parts of the PCB.

Meowsic Keyboard MIDI Adapter Aims For Purrfection

June 14, 2025 by 3 Comments

Both small children and cats have a certain tendency to make loud noises at inopportune times, but what if there were a way to combine these auditory effects? This seems to have been the reasoning behind the creation of the Meowsic keyboard, a children’s keyboard that renders notes as cats’ meows. [Steve Gilissen], an appreciator of unusual electronic instruments, discovered that while there had been projects that turned the Meowsic keyboard into a MIDI output device, no one had yet added MIDI input to it, which of course spurred the creation of his Meowsic MIDI adapter.

The switches in the keys of the original keyboard form a matrix of rows and columns, so that creating a connection between a particular row and column plays a certain note. [Steve]’s plan was to have a microcontroller read MIDI input, then connect the appropriate row and column to play the desired note. The first step was to use a small length of wire to connect rows and columns, thus manually mapping connections to notes. After this tedious step, he designed a PCB that hosts an Arduino Nano to accept input, two MCP23017 GPIO expanders to give it enough outputs, and CD4066BE CMOS switches to trigger the connections.
Continue reading “Meowsic Keyboard MIDI Adapter Aims For Purrfection” →