Bass Bump Headphone Amp

bass-boost-headphone-amp

Headphone amplifiers make for simple, practical electronics projects. The Bass Bump Headphone Amp is no exception, since it’s made out of easy to source parts, and can be built on a proto-board.

We’ve seen many variants of the classic cMoy amplifier, including this pretty one. The Bass Bump differs by providing control over bass frequencies. It does this by putting a filter in front of the amplifier, with a potentiometer to select the mix of frequencies. This goes into a LM386 audio amplifier. At the output is a Zobel network to keep the impedance low at high frequencies. The amplifier can be powered from either a 9V rechargeable battery, or a USB port.

It’s a simple build, but definitely a good one to try on a rainy day. The write up explains how the analog circuitry works, and gives you full instructions on how to build it. After the break, check out a video overview of the project.

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A crystal radio amplifier in a jar

The cool thing with crystal radios is that they are solely powered by the incoming radio waves. However, it usually means listening to your AM radio station with an earpiece and even then, depending on the antenna length, ground connection, and radio station, it can be quite hard to hear.

Even though it is cheating, [Steven] decided to make an amplifier for all the different crystal radios he had made over the years. His design, based on an LM386 amplifier was firstly tested on a breadboard and then permanently soldered onto a perfboard. To make the complete system easy to transport, he opted for a peanut butter jar where he embedded the speaker in the cap. The on/off switch and volume controls are mounted on the side, and easy alligator clips are used for the antenna connection.

The final result is not the one shown in the picture above as [Steven] painted the jar black, giving it a sweet look.

GPS audio tour brought to you by surface speakers

The team at Eschelle Inconnue wanted to “trace a sound cartography of Islam” in Marseilles, France, so they came up with a clever little GPS walking tour powered by an Arduino, MP3 playback module, and a surface transducer speaker.

The team used a Processing app to define geographic areas where each MP3 file would play. An Arduino on the build queries a GPS module and selects the audio file from an MP3 playback module. This isn’t uncommon, and a lot of large outdoor museums (think battlefields) have similar setups.

Determining which audio to play at what location is fairly easy, but that’s not what makes this build special. Instead of simply hooking up a pair of headphones to the build, the team decided to use a surface speaker that turns just about any solid material into a speaker. From the writeup, this is supposed to, “diffuse sounds by giving the illusion to collect them, to listen to the words of the walls, the whisperings through the materials” but we think it’s just a great way to have several people listen to the same audio file at the same time.

PVC boombox is not a potato cannon

After [Luke] built a suitcase mini-ITX rig for LAN parties he was left with one problem: he didn’t have any speakers and he didn’t want to use headphones. Not wanting to do something boring like a USB-powered speaker setup, he built a PVC Boombox.

Built around 3 inch PVC pipe, the boombox houses an off the shelf 15 W amplifier, bluetooth receiver, and charge controller. [Luke] found a deal on a dozen 1400mAh lithium ion batteries and despite the standard, “if you don’t know what you’re doing, don’t use lithium” trope commonly given as advice, he forged ahead anyway. [Luke] picked up a power converter that charges the batteries and provides some protection. The batteries are charged though wall power with a transformer and a huge cap scrounged from an ATX power supply.

[Luke] is pretty pleased with his boombox. Not only does it put out some decent quality sound, the battery life should be tremendous. It’s not a ground-up build, but we think it’s a pretty nice project. [Luke] will be taking the ‘boomtube’ to the Detroit Maker Faire next month, so if you see him make sure to say hi.

Portable SID plays chiptunes

[Markus] on the DangerousPrototypes forum came up with a great little SID player.

The SID was (is?) the awesome sound generation chip inside the Commodore 64, and along with Game Boys and NESs laid the foundation for the chiptune scene. We’re happy to finally see a small SID player that doesn’t resort to SID emulation or a relatively huge MIDIbox.

The SID player itself is a shield on a CUI32 PIC dev board. The PIC32 emulates the 6510 and 6526 CPU and CIA chips found in the Commodore 64. A small USB memory stick stores the High Voltage SID Collection and the file system is navigated with an OLED screen. [Markus] says that the player draws 370 mA, so he runs it off a small wall wart. Still, we’re wondering if it’s possible to run this off of an SD card with a SwinSID so power draw can be reduced and a fully portable SID player can be realized.

We’ve got a touch of nostalgia for chiptune and demoscene music right now, so we’re going to listen to some [Nelly Furtado] [Janne Suni] right now, but you can check out the video demo [Markus] posted after the break.
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Android Talks Pulsewave

Serial communications are a mainstay of digital computing. They don’t require much physical infrastructure and they exist in variations to fit almost any application. The behaviour of serial communications lines, varying from high to low voltage in a timed pattern, is analogous to a 1-bit DAC. Using a whole DAC for serial communication would be a waste in most cases, but the [RobotsEverywhere] team found an exception which you may have encountered already.

Since the audio output of the Android is accessible and addressable, [RobotsEverywhere] wrote source code to use the left and right channels as separate serial communication lines. This circumvents the need to bust into the device and muck about with the hardware which is great if you want a no-risk hack that allows communications to an RS232 port. Any hardware on which you can write to the DAC (and control the sampling rate) is a potential target.

There are some external electronics required to convert the audio signal to TTL, but it’s not very complicated–a couple of comparators and change. You can see it in action after the break.

As a bonus, when you’re done for the day you can plug in your headphones and listen to the soothing poetry of pulse waves all night long.

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Solderless Drawdio Terminally Implemented

So you’re stuck in a boring class and you can’t fight off the urge to hack something, even your pencil, to pass the time. Maybe you are performing a live electronics show and you drop your synth down a flight of stairs and all that you are left with is a handful of components, a screw terminal block and a pencil. There are thousands, perhaps millions of these kinds of situations and for each one the answer is the solderless drawdio clone by [Martin].

You may have seen the original Drawdio here before, a fun piece of technology that is simple enough to recreate. This latest approach would make an excellent introductory project for a hacking workshop seeing as the guide is straightforward and the lack of soldering would make logistics so much easier. The results are very similar to the original–check the video after the break. Continue reading “Solderless Drawdio Terminally Implemented”