We all know that speakers are microphones and microphones are speakers, right? If not, take a moment to plug your headphones into a microphone jack and yell into them. It’s not exactly hi-fi, but it works.
So it’s not a huge surprise that three security researchers in Israel have managed to turn the combination headphone and microphone input jacks that are present on most laptops into an eavesdropping device. (Paper here as PDF, with an obligatory demo video on YouTube, embedded below.) Speake(a)r is a neat proof-of-concept and a horrid pun. Continue reading “Eavesdropping Via Headphones”
Everyone has a chip-of-shame: it’s the part that you know is suboptimal but you keep using it anyway because it just works well enough. Maybe it’s not what you would put into a design that you’re building more than a couple of, but for a quick and dirty lashup, it’s just the ticket. For Hackaday’s [Adam Fabio], that chip is the TIP120 transistor. Truth be told, we have more than one chip of shame, but for audio amplification purposes, it’s the LM386.
The LM386 is an old design, and requires a few supporting passive components to get its best performance, but it’s fundamentally solid. It’s not noise-free and doesn’t run on 3.3 V, but if you can fit a 9 V battery into your project and you need to push a moderate amount of sound out of a speaker, we’ll show you how to get the job done with an LM386.
Continue reading “You Can Have My LM386s When You Pry Them From My Cold Dead Hands”
Everyone likes a good light show, but probably the children of the 60s and 70s appreciate them a bit more. That’s the era when some stereos came with built-in audio oscilloscopes, the search for which led [Tech Moan] to restore an audio monitor oscilloscope and use it to display oscilloscope music.
If the topic of oscilloscope music seems familiar, it may be because we covered [Jerobeam Fenderson]’s scope-driving compositions a while back. The technique will work on any oscilloscope that can handle X- and Y-axis inputs, but analog scopes make for the best display. The Tektronix 760A that [Tech Moan] scrounged off eBay is even better in that it was purpose-built to live in an audio engineer’s console for visualizing stereo audio signals. The vintage of the discontinued instrument isn’t clear, but from the DIPs and discrete components inside, we’ll hazard a guess of early to mid-1980s. The eBay score was a bargain, but only because it was in less that perfect condition, and [Tech Moan] wisely purchased another burned out Tek scope with the same chassis to use for spares.
The restored 760A does a great job playing [Jerobeam]’s simultaneously haunting and annoying compositions; it’s hard to watch animated images playing across the scope’s screen and not marvel at the work put into composing the right signals to make it all happen. Hats off to [Tech Moan] for bringing the instrument back to life, and to [Jerobeam] for music fit for a scope.
Continue reading “Salvaged Scope Lets You Watch the Music”
Halloween has come and gone, but this DIY voice changing Star Wars Stormtrooper helmet tutorial by [Shawn Hymel] is worth a look for a number of reasons. Not only is the whole thing completely self-contained, but the voice changing is done in software thanks to the Teensy’s powerful audio filtering abilities. In addition, the Teensy also takes care of adding the iconic Stormtrooper clicks, pops, and static bursts around the voice-altered speech. Check out the video below to hear it in action.
Besides a microphone and speakers, there’s a Teensy 3.2, a low-cost add-on board for the Teensy that includes a small audio amp, a power supply… and that’s about it. There isn’t a separate WAV board or hacked MP3 player in sight.
Continue reading “Stormtrooper Voice Changer Helmet uses Teensy to Mangle Audio”
[Kedar Nimbalkar] hyperbolically advertises the ultimate cell phone speaker dock. It costs a dollar. It doesn’t need you to pair with it via Bluetooth or WiFi. It pairs extremely fast, 0.000000000001, he clarifies. It may also look like a broken laptop speaker with a stomped wall wart soldered to it, but who can keep up with industrial design trends these days?
He shows us the device in operation. He starts playing some music on his phone’s speaker. It’s not very loud, so he simply lays the phone on the dock. Suddenly, all the audio fidelity a Dell Lattitude from the 90s can provide erupts from the device! How is this done?
Of course, there’s not much to the trick. Since the cellphone speaker is a coil it can induce a small current in another coil. The resulting voltage can be picked up by an audio amplifier and played through the speakers. Nonetheless it’s pretty cool, and we like his suggestion of betting our friends that we could wirelessly pair with their ear buds. Video after the break.
Continue reading “Forget Wifi or Bluetooth, Pair Directly With Your Phone’s Speaker”
There’s been a lot of fuss over Apple’s move to ditch the traditional audio jack. As for me, I hope I never have to plug in another headphone cable. This may come off as gleeful dancing on the gravesite of my enemy before the hole has even been dug; it kind of is. The jack has always been a pain point in my devices. Maybe I’ve just been unlucky. Money was tight growing up. I would save up for a nice set of headphones or an mp3 player only to have the jack go out. It was a clear betrayal and ever since I’ve regarded them with suspicion. Is this the best we could do?
I can’t think of a single good reason not to immediately start dumping the headphone jack. Sure it’s one of the few global standards. Sure it’s simple, but I’m willing to take bets that very few people will miss the era of the 3.5mm audio jack once it’s over. It’s a global episode of the sunk cost fallacy.
In the usual way hindsight is 20/20, the 3.5mm audio jack can be looked at as a workaround, a stop over until we didn’t need it. It appears to be an historic kludge of hack upon hack until something better comes along. When was the last time it was common to hook an Ethernet cable into a laptop? Who would do this when we can get all the bandwidth we want reliably over a wireless connection. Plus, it’s not like most Ethernet cables even meet a spec well enough to meet the speeds they promise. How could anyone reasonably expect the infinitely more subjective and variable headphone and amplifier set to do better?
But rather than just idly trash it, I’d like to make a case against it and paint a possible painless and aurally better future.
Continue reading “Death To The 3.5mm Audio Jack, Long Live Wireless”
On the face of it, playing a vinyl record is a simple process. You simply mount it on a turntable rotating at the right speed, and insert a needle into the groove. A learning exercise for youngsters used to be a passable attempt at a record player on the kitchen table with a pencil, a large cork, a sharpened matchstick, and a piece of paper. It sounded awful, but it demonstrated well how the audio was recorded.
If you have ever looked into the operation of a more conventional turntable though you’ll know that a little more care and attention is needed. There are many factors which affect the quality of the sound, and you quickly become obsessive about tracking, and sources of the tiniest vibration. Someone who has followed this path is [Mjhara], who has made a very high quality turntable. There is an unusual choice in this project: the tonearm is part of the build rather than fitting a commercial item like most turntable projects.
The platter is machined from a piece of rosewood, weighted and balanced with lead shot, and laminated between two sheets of brass. It sits on a bearing aided by a ring of opposing magnets, and is belt driven by a two-phase induction motor. The base of the turntable is cast as a single piece of concrete, the idea being that the extra weight will aid the damping of vibrations. The tonearm is machined from a piece of wood, and its pivot from brass. The tonearm bearing is a ballpoint pen, a surprising yet inspired choice .
Sometimes audiophiles take their quest for better sound to extremes, and justification for their expenditure can be very subjective. But [Mjhara] assures us that this turntable has an exceptionally good sound, and it is certainly a thing of beauty. Full details are in the Imgur gallery embedded below the break.
Continue reading “A Beautiful Turntable With A Heart Of Concrete”