digital audio hacks

742 Articles

Tape-Head Robot Listens To The Floor

December 18, 2016 by 9 Comments

We were just starting to wonder exactly what we’re going to do with our old collection of cassette tapes, and then along comes art robotics to the rescue!

Russian tech artist [::vtol::] came up with another unique device to make us smile. This time, it’s a small remote-controlled, two-wheeled robot. It could almost be a line follower, but instead of detecting the cassette tapes that criss-cross over the floor, it plays whatever it passes by, using two spring-mounted tape heads. Check it out in action in the video below.

Some of the tapes are audiobooks by sci-fi author [Stanislaw Lem] (whom we recommend!), while others are just found tapes. Want to find out what’s on them? Just drive.

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Make Your Eyes Louder With Bluetooth Speaker Goggles

November 20, 2016 by 16 Comments

Your eyes are cool, but they aren’t very loud. You can remedy that with this build from [Sam Freeman]: a pair of Bluetooth speaker goggles. Combine a pair of old welders goggles with a Bluetooth receiver, a small amp and a couple of cheap speaker drivers and you’re well on your way to securing your own jet set radio future.

[Sam] found a set of speaker drivers that were the same size as the lenses of the goggles, as if they were designed for each other. They don’t do much for your vision, but they definitely look cool. [Sam] found that he could run the speakers for an hour or so from a small Lithium Ion battery that’s hidden inside the goggles, along with a large lever switch for that throwback electronics feel. The total cost of this build is a reasonably-low at $40, or less if you use bits from your junk pile.

The real trick is watching them in action and deciding if there’s any motion happening. Don’t get us wrong, they look spectacular but don’t have the visual feedback component of, say, the bass cannon. Look for yourself in the clip below. We might add a pair of googly eyes on the speakers that dance as they move, but that would get away from the more serious Robopunk look that [Sam] is going for. What would you add to build up the aesthetic of these already iconic goggles?

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FingerRing Is Simplest Multichannel Mixer

November 1, 2016 by 16 Comments

It’s hard to make an audio mixer with any less technology than FingerRing (YouTube video, embedded below). We’re pretty sure that [Sergey Kasich] isn’t going to get a patent on this one. But what he does get is our admiration for pushing a simple idea far enough that it’s obviously useful.

The basic idea is transmitting signals using the human body as a conductor. What [Sergey] does is lay out multiple sound sources and sinks on the table, and then play them like a mixer made musical instrument. Pressing harder reduces the resistance, and makes the sound louder. Connecting to two sources mixes them (in you). Watch the video — he gets a lot of mileage out of this one trick.

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Death To The 3.5mm Audio Jack, Long Live Wireless

October 25, 2016 by 360 Comments

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.

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Sending music long distance using laser

Sending Music Long Distance Using A Laser

September 25, 2016 by 48 Comments

This isn’t the first time we’ve seen DIYers sending music over a laser beam but the brothers [Armand] and [Victor] are certainly in contention for sending the music the longest distance, 452 meter/1480 feet from their building, over the tops of a few houses, through a treetop and into a friend’s apartment. The received sound quality is pretty amazing too.

In case you’ve never encountered this before, the light of the laser is modulated with a signal directly from the audio source, making it an analog transmission. The laser is a 250mW diode laser bought from eBay. It’s powered through a 5 volt 7805 voltage regulator fed by a 12V battery. The signal from the sound source enters the circuit through a step-up transformer, isolating it so that no DC from the source enters. The laser’s side of the transformer feeds the base of a transistor. They included a switch so that the current from the regulator can either go through the collector and emitter of the transistor that’s controlled by the sound source, giving a strong modulation, or the current can go directly to the laser while modulation is provided through just the transistor’s base and emitter. The schematic for the circuit is given at the end of their video, which you can see after the break.

They receive the beam in their friend’s apartment using solar cells, which then feed a fairly big amplifier and speakers. From the video you can hear the surprisingly high quality sounds that results. So check it out. It also includes a little Benny Hill humor.

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Now Is The Golden Age Of Artisanal, Non-Traditional Tube Amps

September 24, 2016 by 17 Comments

Earlier in the month, [Elliot Williams] quipped that it had been far too long since we saw a VFD-based amplifier build. Well, that dry spell is over. This week, [kodera2t] started showing off his design for a VFD headphone amp.

Here’s the thing, this isn’t using old surplus vacuum fluorescent displays. This is actually a new part. We first covered it about 18 months ago when Korg and Noritake announced the NuTube. It’s the VFD form factor you would find in old stereo and lab equipment, but housed in the familiar glass case is a triode specifically designed for that purpose.

Check out [kodera2t’s] video below where he walks through the schematic for his amplifier. Since making that video he has populated the boards and taken it for a spin — no video of that yet but we’re going to keep a watchful eye for a follow-up. Since these parts can be reliably sourced he’s even planning to sell it in his Tindie store. If you want to play around with this new tube that’s a pretty easy way to get the tube and support hardware all in one shot. This is not a hack, it’s being used for exactly what Korg and Noritake designed it to do, but we hope to see a few of these kits hacked for specific tastes in amp design. If you do that (or any other VFD hacking) we want to hear about it!

And now for the litany of non-traditional VFD amps we’ve grown to love. There is the Nixie amp where [Elliot] made the quip I mentioned above, here’s an old radio VFD amp project, in this one a VCR was the donor, and this from wayback that gives a great background on how this all works.

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“Nixie” Tubes Sound Good

September 11, 2016 by 11 Comments

A tube is a tube is a tube. If one side emits electrons, another collects them, and a further terminal can block them, you just know that someone’s going to use it as an amplifier. And so when [Asa] had a bunch of odd Russian Numitron tubes on hand, an amplifier was pretty much a foregone conclusion.

A Numitron is a “low-voltage Nixie”, or more correctly a single-digit VFD in a Nixiesque form factor. So you could quibble that there’s nothing new here. But if you dig into the PDF writeup, you’ll find that the tubes have been very nicely characterised, situating this project halfway between dirty hack and quality lab work.

It’s been a while since we’ve run a VFD-based amplifier project, but it’s by no means the first time. Indeed, we seem to run one every couple years. For instance, here is a writeup from 2010, and the next in 2013. Extrapolating forward, you’re going to have to wait until 2019 before you see this topic again.