DIY Hydrophone Listens In On The Deep For Cheap

February 19, 2022 by Tom Nardi 11 Comments

The microphone is a pretty ubiquitous piece of technology that we’re all familiar with, but what if you’re not looking to record audio in the air, and instead want to listen in on what’s happening underwater? That’s a job for a hydrophone! Unfortunately, hydrophones aren’t exactly the kind of thing you’re likely to find at the big-box electronics store. Luckily for us, [Jules Ryckebusch] picked up a few tricks in his 20-year career as a Navy submariner, and has documented his process for building a sensitive hydrophone without needing a military budget.

Fascinated by all the incredible sounds he used to hear hanging around the Sonar Shack, [Jules] pored over documents related to hydrophone design from the Navy and the National Oceanic and Atmospheric Administration (NOAA) until he distilled it all down to a surprisingly straightforward build. The key to the whole build is a commercially available cylindrical piezoelectric transducer designed for underwater communication that, incredibly, costs less than $20 USD a pop.

The transducer is connected to an op-amp board of his own design, which has been adapted from his previous work with condenser microphones. [Jules] designed the 29 x 26 mm board to fit neatly within the diameter of the transducer itself. The entire mic and preamp assembly can be cast inside a cylinder of resin. Specifically, he’s found an affordable two-part resin from Smooth-On that has nearly the same specific gravity as seawater. This allows him to encapsulate all the electronics in a way that’s both impervious to water and almost acoustically transparent. A couple of 3D-printed molds later, the hydrophone was ready to cast.

Interestingly, this isn’t the first homebrew hydrophone we’ve seen. But compared to that earlier entry, which basically just waterproofed a standard microphone pickup, we think this more thoughtful approach is likely to have far better performance.

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Classic IPods Are Super Upgradeable In 2022

February 16, 2022 by Lewin Day 35 Comments

The classic iPod was the MP3 player to beat back in the day, loaded with storage and with its characteristic click-wheel interface. [Ellie] had an iPod Video laying around, one of the more capable models that came out near the end of the product’s run, and set out upgrading it for duty in the pandemic-wracked badlands of 2022.

The iPod in question was a 5.5th generation model, prized for being the last to feature the Wolfson DAC with its good audio quality. [Ellie] used the ever-helpful iFixit guide to learn how to disassemble the device safely. Careful hands and a spudger are key to avoid marring the pressed-together metal case.

Once opened, an iFlash Quad board was installed inside that lets the iPod use up to four micro SD cards for storage instead of the original hard disk drive. With two 512 GB cards installed, [Ellie] won’t be short of storage. A new battery was then subbed in, along with a fancy clear front casing for the aesthetic charm of it all.

After the hardware modifications were complete, the iPod needed to be restored with iTunes to start working again. She then installed the open source Rockbox firmware, which opens up the capabilities of the hardware immensely. Perhaps best of all, it can play DOOM! Alternatively, you can use the clickwheel to control the volume on your MacBook if you so desire.

[Ellie’s] project goes to show that modifying an iPod these days can be a fun weekend build thanks to the great software and hardware now available. It’s wonderful to see that the platform still has such great support years after it has been discontinued. If you really want to look back though, take a gander at the early prototype of Apple’s breakout MP3 player.

Woodworking, Blinkenlites, And FFT’s Dance To The Music

January 18, 2022 by Ryan Flowers 5 Comments

We all have that one project on our minds that we’d love to build if we could just find the right combination of time, energy, and knowledge to dive right in. For [Jonathan], that project was a sound sculpture that’s finally made it from concept to complete. [Jonathan] describes the sound sculpture as the culmination of a decade of learning, and in a moment you’ll understand why.

The sculpture itself is a beautiful display of woodwork mixed with what appear to be individually addressable LED’s. The varying length of the individual enclosures evokes the idea that the sculpture is somehow involved in the sound production, which is a nice touch.

An Adafruit microphone module feeds detected audio into a PSoC 5 microcontroller. You’d expect that [Jonathan] just used one of the FFT libraries that are available. But you’ll recall that this was the culmination of a decade of learning- why so? Because [Jonathan] went through the process of procuring his own grey hairs by writing his own FFT function. A homebrew FFT function and blinkenlites? What’s not to love!

You may also enjoy this discussion of Sine Waves, Square Waves, and FFT’s with our own Bil Herd.

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Mico Is A USB Microphone Based On A Pi Pico

December 25, 2021 by Robin Kearey 20 Comments

When [Mahesh Venkitachalam] was experimenting with machine learning for audio applications on a Raspberry Pi, he found himself looking for a simple USB microphone. A cheap one was easy to find, but the sound quality and directionality left much to be desired. A large, studio-quality mic would be overkill, so [Mahesh] decided to simply build exactly what was needed: a compact, yet high-quality USB microphone that he called Mico.

The sensing device is a MEMS microphone that outputs a pulse density modulated (PDM) signal. There are chips available to directly interface such a microphone to a USB port, but [Mahesh] found them difficult to work with and therefore settled on something he knew already: the Raspberry Pi Pico platform. Luckily, someone had already figured out how to read out a microphone and present a USB device to a PC, so all that was needed was to put all the bits together into a convenient form factor.

The great thing about the Pico platform is that its main controller chip, the RP2040, is available as a separate component. [Mahesh] designed a sleek little PCB that holds the RP2040 along with the MEMS microphone and a USB connector. The end result looks tidy enough that it might have come out of a mass-produced gizmo. Those don’t usually come with full schematics and source code, but the Mico does: everything is available on its GitHub page for anyone to re-use and improve.

You can judge the sound quality for yourself in the video embedded below. If you like DIY USB microphones, you’re in luck: we’ve featured one based on an STM32 as well as a beautiful recreation of a studio-quality mic.

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Know Audio: It All Depends On The DAC

October 20, 2021 by Jenny List 29 Comments

Our trip through the world of audio technology has taken us step-by step from your ears into a typical home Hi-Fi system. We’ve seen the speakers and the amplifier, now it’s time to take a look at what feeds that amplifier.

Here, we encounter the first digital component in our journey outwards from the ear, the Digital to Analogue Converter, or DAC. This circuit, which you’ll find as an integrated circuit, takes the digital information and turns it into the analogue voltage required by the amplifier.

There are many standards for digital audio, but in this context that used by the CD is most common. CDs sample audio at 44.1 kHz 16 bit, which is to say they express the level as a 16-bit number 44100 times per second for each of the stereo channels. There’s an electrical standard called i2s for communicating this data, consisting of a serial data line, a clock line, and an LRclock line that indicates whether the current data is for the left or the right channel. We covered i2s in detail back in 2019, and should you peer into almost any consumer digital audio product you’ll find it somewhere. Continue reading “Know Audio: It All Depends On The DAC” →

3D Printed Preschooler Proof MP3 Player Takes A Beat-ing

October 8, 2021 by Ryan Flowers 9 Comments

Prototyping new ideas can be a lot of fun, but putting new projects in a durable enclosure can be a difficulty. This is especially the case when the user of this product is one of the most destructive forces in nature: A toddler! This is the circumstance that [blue blade] found himself in when he wanted to build a durable MP3 player for his grandson, and you can see the results of his work below the break.

The hardware is simple: A 16850 lithium-ion battery powers an MP3 Decoder/Amplifier module that plays MP3s stored on a Micro SD card. A speaker, power switch, and micro USB powered battery charger complete the build. What stands out most is the enclosure. Why?

When children are involved, durability isn’t a matter of product lifetime, it’s also a matter of safety. Items that are easily broken aren’t just useless, they can be dangerous. With this in mind, [blue blade] built a brightly colored enclosure with extra thick walls joined by metal bolts. Externally, a rounded cover bolts over the charger connector and Micro SD card slot. The only other protrusion is a lighted rocker switch for powering the MP3 player on and off.

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Close up shot of a mechanical sequencer for 555 based synthesizers

Kinetic Synth-Kebab Sculpture Plays Punk Sequentially

October 4, 2021 by Ryan Flowers 12 Comments

What’s better than an Atari Punk Console synthesizer? How about four Atari Punk Console synthesizers. And what better way to present them but as brass wire art sculptures. We’d have forgiven [iSax] if he’d stopped at four brass wire synths, but he took things to another level with his kinetic sculpture that does double duty as a mechanical sequencer. Called the Cyclotone – The Mechanical Punk Console Sequencer, it features wood, brass, brushes, and 555 timers. You can see the demonstration in the video below the break.

If you’re not familiar with the Atari Punk Console, it’s a circuit first described as a “Sound Synthesizer” in Forest Mims’ “Engineer’s Notebook: Integrated Circuit Applications” first published in 1980. It utilized two 555 timers in a single chip, the 556. Later dubbed the “Atari Punk Console”, the circuit has stood the test of time and is still quite popular among hackers of all sorts.

[iSax]’s build adds a sequencing element that allows the synths to be played automatically. The synthesizers are skewered 90 degrees from each other on a square dowel, which is turned at a variable RPM by a stepper motor controlled by a knob at the base of the sculpture.

On either side of each synth is a commutator that contacts salvaged rotary tool brushes which provide power through the hexagonal brass supports. Each synth retains its own speaker and controls and has its own segmented numeral displayed with discrete LED’s that light up when each synth is played.

We applaud [iSax] for a well executed and imaginative build that successfully meshes circuit scultpure, kinetic sculpture, classic electronics and even blinkenlights. If you enjoyed this build, you should also go have a look at a free form Atari Punk Console build and another one built into a joystick. If you come across a project of any kind that catches your fancy, be sure you let us know about it via the Tip Line!

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