digital audio hacks

712 Articles

Aesthetic DIY Bluetooth Speakers

July 30, 2020 by No comments

DIY Bluetooth speaker projects are always a staple here at Hackady. In our latest feature of DIY audio builds, we have [Patrick’s] vinyl cylindrical speaker.

He found a pretty inexpensive Bluetooth audio amplifier on AliExpress. However, the amplifier module oddly enough had a few missing components that were critical to its operation, so he had to do a little bit of re-work. Not something you generally expect to do when you purchase a pre-made module, but he was certainly up to the task.

He noticed the board amp module was missing a battery protection circuit even though there was space on the board laid out for those components (maybe an older board revision?). To remedy this problem, he added his own battery protection circuit to prevent any unwanted catastrophes. Secondly, he noticed a lot of distortion at high volumes and figured that some added capacitance on the power supply would help fix the distortion. Luckily, that did the trick.

Finally, and not quite a mistake on the manufacturer’s part this time, but an improvement [Patrick] needed for his own personal use. He wanted the amp module’s board-level LED indicator to be visible once the enclosure was fitted around the electronics. So, he used the built-in status trigger as a digital signal for a simple transistor circuit powering a much brighter ring LED that could be mounted onto the enclosure. That way, he could utilize the firmware for triggering the board-level status indicator for his own ring LED without any software modifications to the amp module.

Now, all that was left was to construct the enclosure he had 3D-printed and fit all the electronics in their place. We’ve gotten pretty used to the always impressive aesthetics of [Patrick’s] designs, having covered a project of his before, and this build is certainly no exception. Great job!

While you’re here, take a look at some other DIY Bluetooth speaker projects on Hackaday.

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Ljusmaskinen Takes The Rave To The Streets (Eventually)

July 16, 2020 by 6 Comments

When humanity comes out the other side of this pandemic there will be a mountain of awesome projects to show off in person. For instance, this backpack mounted DMX lighting was built to be worn as a mobile rave rig by Swedish hacker [Tim Gremalm]. In-person raves aren’t happening right now but that just means there’s time to add waaaaay to many features to this thing until lockdowns become a thing of the past.

The frame holding the lighting integrates into this backpack and we assume that’s where the battery is stored. The Y-shaped masts hold four PAR lights. Incidentally, that mean parabolic aluminized reflectors, which are commonly used for stage lighting, but in this case the halogen bulbs have been torn out for a trio of 4 W RGBW LEDs. The yellow rectangles are 10 W Chip-on-Board LED panels that serve as strobe lights.

Festmaskinen audio rig in 2015

But merely having the lights does not make it a Rave — this party needs both music and a way to synchronize the lighting effects with it. The music part was already built and used at the West Pride Gothenburg festival (the second largest in Sweden after Stockholm) five years ago. That project, called Festmaskinen, works in conjunction with Ljusmaskinen (the Light Machine). So two people carry the rave on their backs, one with music, the other with the lighting, now that’s a party!

The light controller board uses a set of four Arduino Nano boards along with four voltage regulators to provide control to each of the PAR lights. All of it is stitched together by control from a DMX input board which also controls the COBs. (In this image the DMX board is hidden below the light control board.) Of course you need something that can process the audio and turn it into DMX512 to bring those lighting animations to life and for that he reached for a Raspberry Pi.

[Tim] has a quick demo of the rig at work which we’ve embedded below. What we’re missing is seeing how the top-heavy structure handles when worn as a backpack. Hopefully he’ll be able to get out of his low-ceilinged home and let the stage lights fly before too long!

Hack Together Your Own Bat Signal

July 11, 2020 by 27 Comments

Bats use echolocation to see objects in front of them. They emit an ultrasonic pulse around 20 kHz (and up to 100 kHz) and then sense the pulses as they reflect off an object and back to the bat. It’s the same type of mechanism used by ultrasonic proximity sensors for object-avoidance. Humans (except perhaps the very young ones) can’t hear the ultrasonic pulses since the frequency is too high, but an inexpensive microphone in a simple bat detector could. As it turns out bat detectors are available off the shelf, but where’s the fun in that? So, like any good hacker, [WilkoL] decided to build his own.

[WilkoL’s] design is composed primarily of an electret microphone, microphone preamplifier, CD4040 binary counter, LM386 audio amplifier, and a speaker. Audio signals are analog and their amplitudes vary based on how close the sound is to the microphone. [WilkoL] wanted to pick up bat sounds as far away as possible, so he cranked up the gain of the microphone preamplifier by quite a bit, essentially railing the amplifiers. Since he mostly cares about the frequency of the sound and not the amplitude, he wasn’t concerned about saturating the transistor output.

The CD4040 then divides the signal by a factor of 16, generating an output signal within the audible frequency range of the human ear. A bat signal of 20 kHz divides down to 1.25 kHz and a bat signal of up to 100 kHz divides down to 6.25 kHz.

He was able to test his bat detector with an ultrasonic range finder and by the noise generated from jingling his keychain (apparently there are some pretty non-audible high-frequency components from jingling keys). He hasn’t yet been able to get a recording of his device picking up bats. It has detected bats on a number of occasions, but he was a bit too late to get it on video.

Anyway, we’re definitely looking forward to seeing the bat detector in action! Who knows, maybe he’ll find Batman.

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Your Own Electronic Drum Kit

July 8, 2020 by 6 Comments

[Jake_Of_All_Trades] wanted to take up a new drumming hobby, but he didn’t want to punish his neighbors in the process. He started considering an electric drum kit which would allow him to practice silently but still get some semblance of the real drumming experience.

Unfortunately, electric drum kits are pretty expensive compared to their acoustic counterparts, so buying an electric kit was a bit out of the question. So, like any good hacker, he decided to make his own.

He found a pretty cheap acoustic drum kit on Craigslist and decided to convert it to electric. He thought this would be a perfect opportunity to learn more about electric drum kits in general and would allow him to do as much tweaking as he wanted to in order to personalize his experience. He also figured this would be a great way to get the best of both worlds. He could get an electric kit to practice whenever he wanted without disturbing neighbors and he could easily convert back to acoustic when needed.

First, he had to do a bit of restorative work with the cheap acoustic kit he found on eBay since it was pretty worn. Then, he decided to convert the drum heads to electric using two-ply mesh drum heads made from heavy-duty fiberglass screen mesh. The fiberglass screen mesh was cheap and easy to replace in the event he needed to make repairs. He added drum and cymbal triggers with his own DIY mechanism using a piezoelectric element, similar to another hack we’ve seen. These little sensors are great for converting mechanical to electrical energy and can feed directly into a GPIO to detect when the drum or cymbal was struck. The electrical signal is then interpreted by an on-board signal processing module.

All he needed were some headphones or a small amplifier and he was good to go! Cool hack [Jake_Of_All_Trades]!

While you’re here, check out some of our best DIY musical projects over the years.

DIY Pocket MP3 Player

June 29, 2020 by 13 Comments

When [Neutrino-1] saw DFRobot’s DFPlayer module, he decided he wanted to make his own retro MP3 player. This tiny module comes packed with a ton of interesting capabilities such as EQ adjustment, volume control, and a 3 watt amplifier amongst other things. It can even play ads in between songs, should you want such a thing.

Controlling the DFPlayer module is easy using serial commands from a microcontroller, making it a convenient subsystem in bigger projects, and a potential alternative to the popular VLSI chips or the hard to come by WT2003S IC. [Neutrino-1] does a good job walking readers through the build making it fairly easy to remix, reuse, and reshare.

With the hardware sorted, all you’ve got to do is flash the firmware and load up an SD card with some MP3s. There’s even a small Python GUI to help you get your new player up and running. [Neutrino-1] also introduces users to the U8g2 display library which he says is a bit more feature-rich than the common Adafruit SSD1306 library. Great job [Neutrino-1]!

While you’re here, take a look at some of our other MP3 projects.

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Toddler-Friendly MP3 Player Navigates With Light

June 18, 2020 by 15 Comments

When designing this custom MP3 player for his grandson, [Luc Brun] ran into a unique problem. He wanted the boy to be able to operate the player on his own, but being only 2½ years old, the user interface would have to be exceedingly straightforward. Too many buttons would just be a distraction, and a display with text would be meaningless at his age.

In the end, [Luc] came up with a very interesting way of navigating through directories full of MP3 files using a few push buttons and a ring of WS2812 LEDs. The color of the LEDs indicate which directory or category is currently being selected: spoken nursery rhymes are red, music is orange, nature sounds are yellow, and so on. The number of LEDs lit indicate which file is selected, so in other words, three orange LEDs will indicate the third music track.

At his grandson’s age, we imagine at least a little bit of him navigating through this system is just luck. But as he gets older, he’ll start to form more solid connections between what he’s hearing and the color and number of the LEDs. So not only is this interface a way to help him operate the device himself, but it may serve as a valuable learning tool in these formative years.

On the other hand, if your goal is just to distract a youngster for as long as possible, an overwhelming number of LEDs, buttons, and switches might be exactly what you want.

ESP32 Becomes Music Player In Under 40 Lines Of Code

June 14, 2020 by 60 Comments

The demo code for [XTronical]’s ESP32-based SD card music player is not even 40 lines long, though it will also require a few economical parts before it all works. Nevertheless, making a microcontroller play MP3s (and other formats) from an SD card is considerably simpler today than it was years ago.

Part of what makes this all work is I2S (Inter-IC Sound), a format for communicating PCM audio data between devices. Besides the ESP32, at the heart of it all is an SD card reader breakout board and the MAX98357A, which can be thought of as a combination I2S decoder and Class D amplifier. The ESP32 reads audio files from the SD card and uses an I2S audio library to send the I2S data stream to the MAX98357A (or two of them for stereo.) From there it is decoded automatically and audio gets pumped though attached speakers.

A few economical components, and only a handful of connections between them.

It’s amazing how much easier audio is to work with when one can take advantage of shuffling audio data around digitally, and the decoder handles multiple formats with an amplifier built in. You can see [XTronical]’s ESP32 player in action in the video embedded below.

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