Auto-sleep Hacked in PC Speakers

We can commiserate with [HardwareCoder] who would rather not leave his PC speakers on all the time. The Creative T20 set that he uses turn off when you turn the volume knob all the way down until it clicks. So shutting them off means repositioning the volume each time they’re switched on again. This hack kills two birds with one stone by turning on and off automatically without touching that knob.

The system is based around an ATtiny45 and a few other simple components. It uses two ADCs to monitor the rear input channels of the PC speakers. If no sound is detected for more than one minute, the shutdown pin of the speakers’ amp chip is triggered. That’s not quite where the hack ends. We mentioned it monitors the rear input of the speakers, but it doesn’t monitor the front AUX input. An additional push button is used to disable the auto-sleep when using this front input. There is also a fancy PWM-based heartbeat on an LED when the speakers are sleeping.

[HardwareCoder] was worried that we wouldn’t be interested in this since it’s quite similar to a hack we ran a few years ago. We hope you’ll agree it’s worth another look. He also warned us that the demo video was boring. We watched it all anyway and can confirm that there’s not much action there but we embedded it below anyway.

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Logic Noise: Sawing Away with Analog Waveforms

Today we’ll take a journey into less noisy noise, and leave behind the comfortable digital world that we’ve been living in. The payoff? Smoother sounds, because today we start our trip into analog.

If you remember back to our first session when I was explaining how the basic oscillator loads and unloads a capacitor, triggering the output high or low when it crosses two different thresholds. At the time, we pointed out that there was a triangle waveform being generated, but that you’d have a hard time amplifying it without buffering. Today we buffer, and get that triangle wave out to our amplifiers.

triangle_square

But as long as we’re amplifying, we might as well overdrive the amps and head off to the land of distortion. We’ll do just that and build up a triangle-wave oscillator that can morph into a square wave, passing through a rounded-over kinda square wave along the way. The triangle sounds nice and mellow, and the square wave sounds bright and noisy. (You should be used to them by now…) And we get everything in between.

And while we’re at it, we might as well turn the triangle wave into a sawtooth for that nice buzzy-bass sound. Then we can turn the fat sawtooth into a much brighter sounding pulse wave, a near cousin of the square wave above.

What’s making all this work for us? Some dead-boring amplification with negative feedback, and the (mis-)use of a logic chip to get it. After the break I’ll introduce our Chip of the Day: the 4069UB.

If you somehow missed them, here are the first three installments of Logic Noise:

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Hard Drive… Speakers?

Speakers really aren’t that complex to make. In fact, if you’re clever about it, you can make a speaker out of just about anything. [Afroman] is kicking it old school with a hack he first did back in 2001, but now, in video form: Make your own HDD Speaker!

All you need is an old hard drive you don’t care about anymore, a bit of flexible wire, and an externally powered amplifier (no your cellphone will not work!). If you don’t have an amp, [Afroman] even has a tutorial so you can build your own Class D Amplifier on a breadboard!

First off you’ll need to crack open the HDD enclosure. You might need a torx or hex key to get past the manufacturer’s “safety screws” though. Once it’s open you’ll need to locate the hard drive head — this is the small metal arm that looks kind of like a record player tone arm. It’s actually controlled by a coil, you know, just like a speaker…

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An Upgrade To A Raspberry Pi Media Server

For the last few years, [Luke] has been running a music server with a Raspberry Pi. With the new Raspberry Pi 2 and its quad core processor, he thought it was time for an upgrade.

The build consists of a Raspi 2, a HiFiBerry Dac to address the complaints of terrible audio on the Pi, an aluminum enclosure, and some electronics for IO and a real software shutdown for the Pi. The Arduino also handles an IR remote and a rotary encoder on the front of the enclosure.

The software is the Logitech Media Server along with Squeezeslave. The front end is custom, though, with functions for shutdown and receiving IR remote codes. Everything is served up by Flask, with a 32GB microSD card stuffed into the Pi to store MP3s. All in all, a great build.

DSP 01: Real, Legit Audiophile Goodness

About six months ago, we saw [tshen2]’s work on the DSP 01, a 2-input, 6-output DSP and crossover for extreme audiophiles, and we’re not talking about oxygen free rooms here. The DSP 01 turns a USB audio output into six outputs that will give you perfectly flat eq across bass, mids, and highs, integrates with a 6x100W amplifier, and compensates for room noise. There was a huge update to the project recently and [tshen] is more than happy to share the details

Getting to this phase of the project hasn’t been without its problems. To get the DSP communicating to a computer through a USB port, [tshen2] found a potential solution in the CP2114 USB to I2S Bridge. This device should function as a USB audio sink, translating digital audio into something the DSP understands. This chip did not work in [tshen]’s design. The CP2114 simply does I2S wrong; the I2S spec says the clock must be continuous. This chip implements I2S with a SPI, firmware, and a few other things, making it incompatible with to-spec I2S.

While there was some problems with getting audio in to the device, the core of the device has remained unchanged. [tshen2] is still using the Analog Devices DSP, with the interesting SigmaStudio being used to compensate for the frequency response of the room. This real, legit, science-based audiophile territory here, and an impressive development for a field that – sometimes understandably – doesn’t get the respect it deserves.

We Assume Control: SPI and a Digital Potentiometer

In the last video I demonstrated a Universal Active Filter that I could adjust with a dual-gang potentiometer, here I replace the potentiometer with a processor controlled solid-state potentiometer. For those that are too young to remember, we used to say “solid-state” to differentiate between that and something that used vacuum tubes… mostly we meant you could drop it without it breakage.

The most common way to control the everyday peripheral chips available is through use of one of the common Serial Protocols such as I2C and SPI.  In the before-time back when we had only 8 bits and were lucky if 7 of them worked, we used to have to memory map a peripheral or Input/Output (I/O) controller which means we had to take many control and data lines from the microprocessor such as Data, Address, Read/Write, system clocks and several other signals just to write to a couple of control registers buried in a chip.

Nowadays there is a proliferation of microcontrollers that tend to have built-in serial interface capability it is pretty straightforward to control a full range of peripheral functions; digital and analog alike.  Rather than map each peripheral using said data and address lines,which is a very parallel approach,  the controller communicates with peripherals serially using but a handful of signal lines such as serial data and clock. A major task of old system design, mapping of I/O and peripherals, is no longer needed.

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Making a Homemade Stephen Hawking

It isn’t easy communicating when you have any form of speech impairment. In such cases, a Speech-generating device (SGD) becomes essential to help you talk to the world. When coupled with other ailments that limit body movement, the problem becomes worse. How do you type on a keyboard when you can’t move your hands, and how do you talk when your voice box doesn’t work. Well known Scientist Stephen Hawking has been battling this since 1985. Back then, it took a lot of hardware to build a text entry interface and a text to speech device allowing him to communicate.

But [Marquis de Geek] did a quick hack using just a few parts to make a Voice Box that sounds like Stephen Hawking. Using an arcade push button to act as a single button keyboard, an Arduino, a 74HC595 shift register, a 2-line LCD, and the SP0256 hooked to an audio amplifier / speaker, he built the stand-alone speech synthesizer which sounds just like the voice box that  Stephen Hawking uses. Although Dr. Hawking’s speech hardware is quite complex, [Marquis de Geek]’s hack shows that it’s possible to have similar results using off the shelf parts for a low cost solution.

There aren’t a lot of those SP0256-AL2 chips around. We found just a couple of retailers with small stock levels, so if you want to make one of these voice boxes, better grab those chips while they last. The character entry is not quick, requiring several button presses to get to the character you want to select. But it makes things easier for someone who cannot move their hands or use all fingers. A lot of kids grew up using Speak and Spell, but the hardware inside that box wasn’t the easiest to hack into. For a demo of [Marquis de Geek]’s homemade Hawking voice box, check the video below.

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