Friday Hack Chat: Audio Amplifier Design

March 29, 2017 by Mike Szczys 2 Comments

Join [Jørgen Kragh Jakobsen], Analog/digital Design Engineer at Merus-Audio, for this week’s Hack Chat.

Every week, we find a few interesting people making the things that make the things that make all the things, sit them down in front of a computer, and get them to spill the beans on how modern manufacturing and technology actually happens. This is the Hack Chat, and it’s happening this Friday, March 31, at noon PDT (20:00 UTC).

Jørgen’s company has developed a line of multi level Class D amplifiers that focus on power reduction to save battery life in mobile application without losing audio quality.

There are a lot of tricks to bring down power consumption, some on core technologies on transistor switching, others based on input level where modulation type and frequency is dynamically changed to fit everything from background audio level to party mode.

Here’s How To Take Part:

Our Hack Chats are live community events on the Hackaday.io Hack Chat group messaging.

Log into Hackaday.io, visit that page, and look for the ‘Join this Project’ Button. Once you’re part of the project, the button will change to ‘Team Messaging’, which takes you directly to the Hack Chat.

You don’t have to wait until Friday; join whenever you want and you can see what the community is talking about.

Upcoming Hack Chats

We’ve got a lot on the table when it comes to our Hack Chats. On April 7th, our host will be [Samy Kamkar], hacker extraordinaire, to talk reverse engineering.

[Joe Grand’s] Toothbrush Plays Music That Doesn’t Suck

March 27, 2017 by Mike Szczys 40 Comments

It’s not too exciting that [Joe Grand] has a toothbrush that plays music inside your head. That’s actually a trick that the manufacturer pulled off. It’s that [Joe] gave his toothbrush an SD card slot for music that doesn’t suck.

The ~~victim~~ donor hardware for this project is a toothbrush meant for kids called Tooth Tunes. They’ve been around for years, but unless you’re a kid (or a parent of one) you’ve never heard of them. That’s because they generally play the saccharine sounds of Hannah Montana and the Jonas Brothers which make adults choose cavities over dental health. However, we’re inclined to brush the enamel right off of our teeth if we can listen to The Amp Hour, Embedded FM, or the Spark Gap while doing so. Yes, we’re advocating for a bone-conducting, podcasting toothbrush.

[Joe’s] hack starts by cracking open the neck of the brush to cut the wires going to a transducer behind the brushes (his first attempt is ugly but the final process is clean and minimal). This allows him to pull out the guts from the sealed battery compartment in the handle. In true [Grand] fashion he rolled a replacement PCB that fits in the original footprint, adding an SD card and replacing the original microcontroller with an ATtiny85. He goes the extra mile of making this hack a polished work by also designing in an On/Off controller (MAX16054) which delivers the tiny standby current needed to prevent the batteries from going flat in the medicine cabinet.

Check out his video showcasing the hack below. You don’t get an audio demo because you have to press the thing against the bones in your skull to hear it. The OEM meant for this to press against your teeth, but now we want to play with them for our own hacks. Baseball cap headphones via bone conduction? Maybe.

Update: [Joe] wrote in to tell us he published a demonstration of the audio. It uses a metal box as a sounding chamber in place of the bones in our head.

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The Hard Way Of Cassette Tape Auto-Reverse

March 23, 2017 by Lewin Day 71 Comments

The audio cassette is an audio format that presented a variety of engineering challenges during its tenure. One of the biggest at the time was that listeners had to physically remove the cassette and flip it over to listen to the full recording. Over the years, manufacturers developed a variety of “auto-reverse” systems that allowed a cassette deck to play a full tape without user intervention. This video covers how Akai did it – the hard way.

Towards the end of the cassette era, most manufacturers had decided on a relatively simple system of having the head assembly rotate while reversing the motor direction. Many years prior to this, however, Akai’s system involved a shuttle which carried the tape up to a rotating arm that flipped the cassette, before shuttling it back down and reinserting it into the deck.

Even a regular cassette player has an astounding level of complexity using simple electromechanical components — the humble cassette precedes the widespread introduction of integrated circuits, so things were done with motors, cams, levers, and switches instead. This device takes it to another level, and [Techmoan] does a great job of showing it in close-up detail. This is certainly a formidable design from an era that’s beginning to fade into history.

The video (found after the break) also does a great job of showing glimpses of other creative auto-reverse solutions — including one from Phillips that appears to rely on bouncing tapes through something vaguely resembling a playground slide. We’d love to see that one in action, too.

One thing you should never do with a cassette deck like this is use it with a cassette audio adapter like this one.

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Neural Network Composes Music; Says “I’ll Be Bach”

March 17, 2017 by Donald Papp 36 Comments

[carykh] took a dive into neural networks, training a computer to replicate Baroque music. The results are as interesting as the process he used. Instead of feeding Shakespeare (for example) to a neural network and marveling at how Shakespeare-y the text output looks, the process converts Bach’s music into a text format and feeds that to the neural network. There is one character for each key on the piano, making for an 88 character alphabet used during the training. The neural net then runs wild and the results are turned back to audio to see (or hear as it were) how much the output sounds like Bach.

The video embedded below starts with a bit of a skit but hang in there because once you hit the 90 second mark things get interesting. Those lacking patience can just skip to the demo; hear original Bach followed by early results (4:14) and compare to the results of a full day of training (11:36) on Bach with some Mozart mixed in for variety. For a system completely ignorant of any bigger-picture concepts such as melody, the results are not only recognizable as music but can even be pleasant to listen to.

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DreamBlaster X2 on a Sound Blaster Sound Card

DreamBlaster X2: A Modern MIDI Synth For Your Sound Blaster Card

January 21, 2017 by Eric Evenchick 24 Comments

Back in the 90s, gamers loaded out their PCs with Creative’s Sound Blaster family of sound cards. Those who were really serious about audio could connect a daughterboard called the Creative Wave Blaster. This card used wavetable synthesis to provide more realistic instrument sounds than the Sound Blaster’s on board Yamaha FM synthesis chip.

The DreamBlaster X2 is a modern daughterboard for Sound Blaster sound cards. Using the connector on the sound card, it has stereo audio input and MIDI input and output. If you’re not using a Sound Blaster, a 3.5 mm jack and USB MIDI are provided. Since the MIDI uses TTL voltages, it can be directly connected to an Arduino or Raspberry Pi.

This card uses a Dream SAM5000 series DSP chip, which can perform wavetable synthesis with up to 81 polyphonic voices. It also performs reverb, chorus, and equalizer effects. This chip sends audio data to a 24 bit DAC, which outputs audio into the sound card or out the 3.5 mm jack.

The DreamBlaster X2 also comes with software to load wavetables, and wavetables to try out. We believe it will be the best upgrade for your 486 released in 2017. If you’re interested, you can order an assembled DreamBlaster. After the break, a review with audio demos.

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Circuit Bent CD Player Is Glitch Heaven

January 1, 2017 by Lewin Day 19 Comments

Circuit bending is the art of creatively short circuiting low voltage hardware to create interesting and unexpected results. It’s generally applied to things like Furbys, old Casio keyboards, or early consoles to create audio and video glitches for artistic effect. It’s often practiced with a random approach, but by bringing in a little knowledge, you can get astounding results. [r20029] decided to apply her knowledge of CD players and RAM to create this glitched out Sony Discman.

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Lo-Fi Greeting Card Sampler

December 24, 2016 by Lewin Day 8 Comments

We’re all familiar with record-your-own-message greeting cards. Generally they’re little more than a cute gimmick for a friend’s birthday, but [dögenigt] saw that these cards had more potential.

After sourcing a couple of cheap modules from eBay, the first order of business was to replace the watch batteries with a DC power supply. Following the art of circuit bending, he then set about probing contacts on the board. Looking to control the pitch of the recorded message, [dögenigt] found two pads that when touched, changed the speed of playback. Wiring these two points to the ears of a potentiometer allowed the pitch to be varied continously. Not yet satisfied, [dögenigt] wanted to enable looped playback, and found a pin that went low when the message was finished playing. Wiring this back to the play button allowed the recording to loop continuously.

[dögenigt] now has a neat little sampler on his hands for less than $10 in parts. To top it off, he housed it all in a sweet 70s intercom enclosure, using the Call button to activate recording, and even made it light sensitive with an LDR.

We’ve seen a few interesting circuit bends over the years – check out this digitally bent Roland TR-626 or this classic hacked Furby.

Check out the video under the break.

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