The Cassette MP3 Player

1994 was twenty years ago. There are people eligible to vote who vaguely remember only one Bush presidency. You can have a conversation with someone born after the millennium, and they think a 3.5 inch disk is called a save icon. Starting to feel old? Don’t worry, all the trinkets of your youth have now become shells for MP3 players, the cassette tape included.

[Britt] is aware you can pick up one of these cassette tape MP3 players through the usual channels, but she wanted her build to be a little different. She’s using ar real, vintage cassette tape for starters, and from the outside, looks pretty much like any other cassette tape: there’s a thin strip of tape at the bottom, and the clear plastic window shows the tape is at the beginning of side A.

Outside appearances are just that; inside, there is a small, repurposed MP3 player, with tact switches wired up to the old buttons, actuated by moving the spools back and forth. Yes, you actually play, pause, rewind and fast forward by sticking a pencil in the spool and moving it back and forth. Amazing.

It’s a great build, and considering both cassette tapes and cheap MP3 players can be found in the trash these days, it’s something that should be hard to replicate.

Acoustic Impulse Marker Tracks Sounds With a Pencil

Acoustic Impulse Marker (aiming device)

Two students at Cornell University have put together a rather curious sound tracking device called an Acoustic Impulse Marker.

[Adam Wrobel] and [Michael Grisanti] study electrical and computer science, and for their final microcontroller class they decided to build this device using the venerable ATmega 1284p.

The system uses a three-microphone array to accurately position sharp noises within 5 degrees of accuracy. The microcontroller detects the “acoustic delay” between the microphones which allows it to identify the location of the sound’s source vector. It does this using an 8-stage analog system which converts the sounds from each microphone into a binary signal, which identifies when each microphone heard the noise. The resultant 3 binary signals are then compared for their time delay, it selects the two closest microphones, and then does a simple angle calculation based on the magnitudes of each to determine the sounds position. Continue reading “Acoustic Impulse Marker Tracks Sounds With a Pencil”

The Teensy Audio Library

There are a few ways of playing .WAV files with a microcontroller, but other than that, doing any sort of serious audio processing has required a significantly beefier processor. This isn’t the case anymore: [Paul Stoffregen] has just released his Teensy Audio Library, a library for the ARM Cortex M4 found in the Teensy 3 that does WAV playback and recording, synthesis, analysis, effects, filtering, mixing, and internal signal routing in CD quality audio.

This is an impressive bit of code, made possible only because of the ARM Cortex M4 DSP instructions found in the Teensy 3.1. It won’t run on an 8-bit micro, or even the Cortex M3-based Arduino Due. This is a project meant for the Teensy, although [Paul] has open sourced everything and put it up on Github. There’s also a neat little audio adapter board for the Teensy 3 with a microSD card holder, a 1/8″ jack, and a connector for a microphone.

In addition to audio recording and playback, there’s also a great FFT object that will split your audio spectrum into 512 bins, updated at 86Hz. If you want a sound reactive LED project, there ‘ya go. There’s also a fair bit of synthesis functions for sine, saw, triangle, square, pulse, and arbitrary waveforms, a few effects functions for chorus, flanging, envelope filters, and a GUI audio system design tool that will output code directly to the Arduino IDE for uploading to the Teensy.

It’s really an incredible amount of work, and with the number of features that went into this, we can easily see the quality of homebrew musical instruments increasing drastically over the next few months. This thing has DIY Akai MPC/Monome, psuedo-analog synth, or portable effects box written all over it.

Finding a Shell in a Bose SoundTouch

Bose, every salesperson’s favorite stereo manufacturer, has a line of WiFi connected systems available. It’s an impressively innovative product, able to connect to Internet Radio, Pandora, music libraries stored elsewhere on the network. A really great idea, and since this connects to a bunch of web services, you just know there’s a Linux shell in there somewhere. [Michael] found it.

The SoundTouch is actually rather easy to get into. The only real work to be done is connecting to port 17000, turning remote services on, and then connecting with telnet. The username is root.

The telnet service on port 17000 is actually pretty interesting, and we’re guessing this is what the SoundTouch iOS app uses for all its wizardry. [Michael] put a listing of the ‘help’ command up on pastebin, and it looks like there are commands for toggling GPIOs, futzing around with Pandora, and references to a Bluetooth module.

Interestingly, when [Michael] first suspected there could be Linux inside this box, he contacted Bose support for any information. He figured out how to get in on his own, before Bose emailed him back saying the information is proprietary in nature.

The LPT DAC

About 30 years ago, before every computer had CD quality audio built in, audio cards and chips were technological marvels. MIDI chips, FM synthesis, and synths on a chip reigned supreme but one little device – just a handful of resistors – sounded fantastic. it was the Covox Speech Thing, a simple resistor ladder wired up to the parallel port of a computer that would output 8-bit audio to an external amplifier. [FK] recently built his own Covox (Czech, Google translatrix) with just 18 resistors, and the results sound fantastic.

Instead of fancy chips, the original Covox Speech Thing used the 8 bit parallel port on a PC. Back in the olden days, this was the fastest way to get digital data out of a computer, but since it was digital only, a DAC was required to turn this into audio. A simple resistor ladder was sufficient, and this hardware was eventually supported by the old DOS games from Sierra and Id.

[FK] has a demo of this LPT DAC available here, but we’re not thinking that link will last long. If anyone has a better link, leave a note in the comments and we’ll update this post. Thanks [beavel] for sending this in.

Reanimating a Philips HDD 1420 MP3 Player

[OiD] had a dusty, old, forgotten Philips HDD1420 GoGear mp3 player kicking around his place. As you can imagine, the battery was dead. He had no charger or connector for the thing, but decided to try to resurrect it anyway.

He thought it would simply be a matter of providing alternative power, but the GoGear wasn’t having it and insisted on being connected to a computer. He had some luck consulting Pinouts.ru and found Philips’ own device manager software, but it still wasn’t easy. The device manager doesn’t work on Windows 7. He tried an XP box, but it didn’t detect the device.

Finally, he discovered that the hard drive was kaput and replaced it with an 8GB Microdrive. That helped, but he still had a hard row to hoe. [OiD] formatted the new HD and gave it the official firmware, but still had to replace some system files according to the Philips manual. He ended up using RockBox to reanimate it and decided to keep it on the device.

There was still an issue with charging, though. It has an IC that handles selection of either the proprietary external adapter or USB power, but the RockBox firmware doesn’t implement switching and defaults to the adapter. Several tweaks and a hacked-in mini USB later, the patient is in stable condition and cranking out the tunes.

Levitating Speaker Plays Back Eerie Recordings

Let’s face it, levitating anything is pretty fascinating — especially when you think there should be wires. This project puts a new spin on magnetic levitation by using a PID controller to levitate a speaker while it plays music!

It uses the standard levitation setup — an electromagnet, a permanent magnet, and a hall effect sensor. A microcontroller implements the PID system, varying the current supplied to the electromagnet to keep the speaker floating at just the right height. Music is wirelessly transmitted to the speaker via Bluetooth, but unfortunately the speaker’s power is not. It features a small lithium ion battery which has a run-time of around 5 hours before it has to be recharged manually.

As you’ll notice in the following video, having a floating speaker has a pretty interesting effect — especially when it starts spinning.

Continue reading “Levitating Speaker Plays Back Eerie Recordings”