Sending Music Long Distance Using A Laser

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

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

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.

Seeed Studio’s ReSpeaker Speaks All the Voice Recognition Languages

Seeed Studio recently launched its third Kickstarter campaign: ReSpeaker, an open hardware voice interface. After their previous Kickstarted IoT hardware, such as the RePhone, mostly focused on connectivity, the electronics manufacturer from Shenzhen now tackles another highly contested area of IoT: Voice recognition.

The ReSpeaker Core is a capable development board based on Mediatek’s MT7688 WiFi module and runs OpenWrt. Onboard is a WM8960 stereo audio codec with integrated 1W speaker/headphone driver, a microphone, an ATMega32U4 coprocessor, 12 addressable RGB LEDs and 8 touch sensors. There are also two expansion headers with GPIOs, I2S, I2C, analog audio and USB 2.0 and an onboard microSD card slot.

The latter is especially useful to feed the ReSpeaker’s integrated speech recognition engine PocketSphinx with a vocabulary and audio file library, enabling it to respond to keywords and commands even when it’s not hooked up to the internet. Once it’s online, ReSpeaker also supports most of the available cloud based cognitive speech recognition services, such as Microsoft Cognitive Service, Amazon Alexa Voice Service, Google Speech API, Wit.ai and Houndify. It also comes with an SDK and Python API, supports JavaScript, Lua and C/C++, and it looks like the coprocessor features an Arduino-compatible bootloader.

The expansion header accepts shield-like hardware add-ons. Some of them are also available through the campaign. The most important one is the circular, far-field microphone array. Based on 7 XVSM-2000 respeaker_meow2digital microphones, the extension board enhances the device’s hearing with sound localization, beam forming, reverb and noise suppression. A Grove extension board connects the ReSpeaker to the Seeed’s current lineup on ready-to-use sensors, actuators and other peripherals.

Seeed also cooperates with the Meow King Audio Electronic Company to develop a nice tower-shaped enclosure with built-in speaker, 5W amplifier and battery. As a portable speaker, the Meow King Drive Unit (shown on the right) certainly doesn’t knock your socks off, but it practically turns the ReSpeaker into an open source version of the Amazon Echo — including the ability to run offline instead of piping everything you say to Big Brother.

According to Seeed, the freshly baked hardware will ship to backers in November 2016, and they do have a track-record of on-schedule shipped Kickstarter rewards. At the time of writing, some of the Crazy Early Birds are still available for $39. Enjoy the campaign video below and let us know what you think of think hardware in the comments!

Bone Conduction Skull Radio

There are many ways to take an electrical audio signal and turn it into something you can hear. Moving coil speakers, plasma domes, electrostatic speakers, piezo horns, the list goes on. Last week at the Electromagnetic Field festival in the UK, we encountered another we hadn’t experienced directly before. Bite on a brass rod (sheathed in a drinking straw for hygiene), hear music.

The TOG Skull Radio demo box
The TOG Skull Radio demo box

This was Skull Radio, a bone conduction speaker courtesy of [Tdr], one of our friends from TOG hackerspace in Dublin, and its simplicity hid a rather surprising performance. A small DC motor has its shaft connected to a piece of rod, and a small audio power amplifier drives the motor. Nothing is audible until you bite on the rod, and then you can hear the music. The bones of your skull are conducting it directly to your inner ear, without an airborne sound wave in sight.

The resulting experience is a sonic cathedral from lips of etherial sibilance, a wider soft palate soundstage broadened by a tongue of bass and masticated by a driving treble overlaid with a toothy resonance before spitting out a dynamic oral texture. You’ll go back to your hi-fi after listening to [Tdr]’s Skull Radio, but you’ll know you’ll never equal its unique sound.

(If you are not the kind of audiophile who spends $1000 on a USB cable, the last paragraph means you bite on it, you hear music, and it sounds not quite as bad as you might expect.)

This isn’t the first bone conduction project we’ve featured here, we’ve seen a Bluetooth speaker and at least one set of headphones, but our favorite is probably this covert radio.

Keytar Made Out Of A Scanner To Make Even the 80s Jealous

Do any of you stay awake at night agonizing over how the keytar could get even cooler? The 80s are over, so we know none of us do. Yet here we are, [James Cochrane] has gone out and turned a HP ScanJet Keytar for no apparent reason other than he thought it’d be cool. Don’t bring the 80’s back [James], the world is still recovering from the last time.

Kidding aside (except for the part of not bringing the 80s back), the keytar build is simple, but pretty cool. [James] took an Arduino, a MIDI interface, and a stepper motor driver and integrated it into some of the scanner’s original features. The travel that used to run the optics back and forth now produce the sound; the case of the scanner provides the resonance. He uses a sensor to detect when he’s at the end of the scanner’s travel and it instantly reverses to avoid collision.

A off-the-shelf MIDI keyboard acts as the input for the instrument. As you can hear in the video after the break; it’s not the worst sounding instrument in this age of digital music. As a bonus, he has an additional tutorial on making any stepper motor a MIDI device at the end of the video.

If you don’t have an HP ScanJet lying around, but you are up to your ears in surplus Commodore 64s, we’ve got another build you should check out.

Hacklet 116 – Audio Projects

If the first circuit a hacker builds is an LED blinker, the second one has to be a noisemaker of some sort. From simple buzzers to the fabled Atari punk console, and guitar effects to digitizing circuits, hackers, makers and engineers have been building incredible audio projects for decades. This week the Hacklet covers some of the best audio projects on Hackaday.io!

vumeterWe start with [K.C. Lee] and Automatic audio source switching. Two audio sources, one amplifier and speaker system; this is the problem [K.C. Lee] is facing. He listens to audio from his computer and TV, but doesn’t need to have both connected at the same time. Currently he’s using a DPDT switch to change inputs. Rather than manually flip the switch, [K.C. Lee] created this project to automatically swap sources for him. He’s using an STM32F030F4 ARM processor as the brains of the operation. The ADCs on the microcontroller monitor both sources and pick the currently active one. With all that processing power, and a Nokia LCD as an output, it would be a crime to not add some cool features. The source switcher also displays a spectrum analyzer, a VU meter, date, and time. It even will attenuate loud sources like webpages that start blasting audio.

 

muzzNext up is [Adam Vadala-Roth] with Audio Blox: Experiments in Analog Audio Design. [Adam] has 32 projects and counting up on Hackaday.io. His interests cover everything from LEDs to 3D printing to solar to hydroponics. Audio Blox is a project he uses as his engineer’s notebook for analog audio projects. It is a great way to view a hacker figuring out what works and what doesn’t. His current project is a 4 board modular version of the Big Muff Pi guitar pedal. He’s broken this classic guitar effect down to an input board, a clipping board, a tone control, and an output stage. His PCB layouts, schematics, and explanations are always a treat to view and read!

pauldioNext we have [Paul Stoffregen] with Teensy Audio Library. For those not in the know, [Paul] is the creator of the Teensy family of boards, which started as an Arduino on steroids, and has morphed into something even more powerful. This project documents the audio library [Paul] created for the Freescale/NXP ARM processor which powers the Teensy 3.1. Multiple audio files playing at once, delays, and effects, are just a few things this library can do. If you’re new to the audio library, definitely check out [Paul’s] companion project
Microcontroller Audio Workshop & HaD Supercon 2015. This project is an online version of the workshop [Paul] ran at the 2015 Hackaday Supercon in San Francisco.

drdacFinally we have [drewrisinger] with DrDAC USB Audio DAC. DrDac is a high quality DAC board which provides a USB powered audio output for any PC. Computers these days are built down to a price. This means that lower quality audio components are often used. Couple this with the fact that computers are an electrically noisy place, and you get less than stellar audio. Good enough for the masses, but not quite up to par if you want to listen to studio quality audio. DrDAC houses a PCM2706 audio DAC and quality support components in a 3D printed case. DrDAC was inspired by [cobaltmute’s] pupDAC.

If you want to see more audio projects and hacks, check out our new audio projects list. See a project I might have missed? Don’t be shy, just drop me a message on Hackaday.io. That’s it for this week’s Hacklet, As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!