It’s A TV-Scope-Guitar Amplifier!

Guitar amplifiers are a frequent project, and despite being little more than a simple audio amplifier on paper, they conceal a surprising quantity of variables in search of a particular sound. We’ve seen a lot of them, but never one quite like [Nate Croson]’s CRT TV guitar amplifier. The LM386 doesn’t just drive the speaker, he’s also using it to turn the TV into a crude oscilloscope to form a visualisation of the sound.

The video showing this feat is below the break, and it puts us in a quandary due to being short on technical information. He’s driving the horizontal coils with the TV’s 50 Hz sawtooth field timebase, and the vertical ones with the audio from the LM386. We aren’t sure whether he’s rotated the yoke or whether the connections have been swapped, but the result is certainly impressive.

So given that there’s not quite as much technical detail as we’d like, why has this project captured our interest? Because it serves as a reminder that a CRT TV is a bit more than a useless anachronism, it’s a complex analogue device with significant and unique hacking potential. The older ones in particular provide endless possibilities for modification and circuit bending, and make for a fascinating analogue playground at a very agreeable price. It’s worth pointing out however that some of the voltages involved can make them a hazardous prospect for the unwary hacker. If you’re interested though, take a look at our dive into an older model.

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A Unique Microphone Preamp

We live in a world in which nearly any kind of gadget or tool you can imagine is just a few clicks away. In many respects, this has helped fuel the maker culture over the last decade or so; now that people aren’t limited to the hardware that’s available locally, they’re able to create bigger and better things than ever before. But it can also have a detrimental effect. One has to question, for instance, why they should go through the trouble of building something themselves when they could buy it, often for less than the cost of the individual components.

The critic could argue that many of the projects that grace the pages of Hackaday could be supplanted with commercially available counterparts. We don’t deny it. But the difference between buying a turn-key product and building an alternative yourself is that you can make it exactly how you want it. That is precisely why [Sam Izdat] created this truly one of a kind microphone preamplifier. Could he have bought one online for cheaper? Probably. Could he have saved himself an immense amount of time and effort? Undoubtedly. Do we care? Not in the slightest.

The amplifier is based on the Texas Instruments INA217 chip, with an Arduino Nano and 128×64 OLED display providing the visualization. [Sam] was able to find a bare PCB for a typical INA217 implementation on eBay for a few bucks (see what we mean?), which helped get him started and allowed him to spend more time on the software side of things. His visualization code offers a number of interesting display modes, uses Fast Hartley Transforms, and very nearly maxes out the Arduino.

But perhaps no element of this build is as unique as the case. The rationale behind the design is that [Sam] wanted to compartmentalize each section of the device (power supply, amplifier, visualization) to avoid any interference. The cylindrical shapes were an issue of practicality: the compartments were constructed by using a hole saw to make wooden discs, which were then glued together and hollowed out. The case was stained and coated with polyurethane, but due to some slightly overzealous use of glue and fillers, the coloring isn’t uniform. This gives the final piece a somewhat weathered look, in sharp contrast to the decidedly high-tech looking display.

Overall, this build reminds us of the modular 3D printed amplifier we saw earlier in the year combined with these speaker-integrated Arduino VU meters.

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Dancing Mandelbrot Set On A FPGA

This FPGA based build creates an interesting display which reacts to music. [Wancheng’s] Dancing Mandelbrot Set uses an FPGA and some math to generate a controllable fractal display.

The build produces a Mandelbrot Set with colours that are modified by an audio input. The Terasic DE2-115 development board, which hosts a Cyclone IV FPGA, provides all the IO and processing. On the input side, UART or an IR remote can be used to zoom in and out on the display. An audio input maps to the color control, and a VGA output allows for the result to be displayed in real time.

Dancing Mandelbrot Block DiagramOn the FPGA, a custom calculation engine, running at up to 150 MHz, does the math to generate the fractal. A Fast Fourier transform decomposes the audio input into frequencies, which are used to control the colors of the output image.

This build is best explained by watching, so check out the video after the break.

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These Trackpad Winamp Visualizations Really Whip The Llama’s Ass

As much as we like a good clean Model M specimen, those curly-corded clicky behemoths are somewhat lacking for certain flavors of gaming. There aren’t any blank keys to override, and there sure isn’t a full-color trackpad that you can write apps for. [Gus] has such a keyboard: the Razer Deathstalker Ultimate which features the SwitchBlade UI. He made himself this sweet audio visualizer for it that extends Winamp visualizations to the Switchblade UI.

[Gus]’s hack is built on the Tiny3D visualization framework. It does what you might expect—reads the visualization values, sets them up for display on the trackpad, and renders them to said trackpad. [Gus] uses some of the 10 programmable keys to change colors on the fly, and the result is pretty awesome. As [Gus] points out, this is just the beginning of what the plugin can do. You’ll need the Razer SDK to get started, and you can get the other ingredients from [Gus]’s repo. Once you’re done with this, you could try auto-dimming your keyboard backlight.

Of course there are demo videos after the jump. Come on.

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Using An LED Cube As An Audio Visualizer

[Isaac] sent in his mashup build of a LED cube combined with a graphic EQ meter. The build is fairly simple and from the video we can tell that his build would be a great installation in a dubstep venue. While it’s not the 9x9x9 cube possible with some judicious coding we think it’s a very fitting display for the intended purpose.

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Mac SE/30 Audio Visualizer


Sure, you could make it into a web server, but [markie] sent me his Mac SE/30 visualizer. It was inspired by another’s mac mod, but he was kind enough to write up an entire how-to. The audio signal was run directly into the deflection coils on the macs tubes. The mod is so simple, I might have to pick one up just for CRT experimentation.

[The next regular podcast cometh, but It’s delayed by my cold.]