Lo-Fi Fun: Beer Can Microphones

December 27, 2022 by Kristina Panos 16 Comments

Sometimes, you just need an easy win, right? This is one of those projects. A couple months back, I was looking at my guitars and guitar accessories and thought, it is finally time to do something with the neck I’ve had lying around for years. In trying to decide a suitable body for the slapdash guitar I was about to build, I found myself at a tractor supply store for LEGO-related reasons. (Where else are you going to get a bunch of egg cartons without eating a bunch of eggs?) I noticed that they happened to also stock ammo boxes. Bam! It’s sturdy, it opens easily, and it’s (very) roughly guitar body shaped. I happily picked one up and started scheming on the way home.

Having never built a cigar box guitar before and being of a certain vintage, I’m inclined to turn to books instead of the Internet, so I stocked up from the library. Among my early choices was Making Poor Man’s Guitars by Shane Speal, who is widely considered to be the guru on the subject. In flipping through the book, I noticed the beer can microphone project and was immediately taken by the aesthetic of some cool old 70s beer can with a 1/4″ instrument jack on the bottom, just asking for some dirty blues to be belted into it. I had to build one. Or twelve.

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A Simple High-Fidelity DIY Mic Pre Amp

December 16, 2022 by Lewin Day 13 Comments

If you’re doing any serious work with microphones, you’ll typically find yourself in want of a dedicated preamp. [ojg] needed just such a thing for acoustic measurement duties, and set about working up a cheap DIY design by the name of ThatMicPre.

The design is based around the THAT1510 preamp IC, known for its good frequency response and low harmonic distortion and noise. The design is also compatible with THAT1512, SSM2019, and INA217 chips as well. [ojg] gave the design switch-controlled gain levels, providing greater accuracy than a potentiometer adjustment, and the ability to supply phantom power for mics that require it. The PCB is designed to rely on through-hole parts and common connectors for easy assembly.

The design is open source, and has already been built by others on the DIYAudio forums. Built into a simple case, it looks like a handsome and well-built piece of audio equipment. We’ve featured quite a few unique preamps over the years, and if you’ve been building your own, we’d love to see those too!

Camera-Mounted Stereo Mic Is Fluffy And Capable

October 2, 2022 by Lewin Day 10 Comments

Typically, the audio coming out of your camera is not of the greatest quality. An external mic is generally a great upgrade, and this build from [DJJules] aims to be just that.

It’s a stereo mic setup based on the work of the Office de Radiodiffusion Télévision Française, or ORTF. The ORTF stereo technique defines using two cardioid mics pointing left and right at a seperation of 110 degrees and 17 cm apart, which captures a quality stereo field that also sounds good when presented as a mono mixdown.

The build uses a simple wooden frame to hold two electret mic capsules in the required orientation. They’re wired up to a 3.5mm jack so they can be plugged straight into a mic input on a DSLR or other similarly-equipped camera. Hair curlers covered in faux fur are used as a wind shield for the mics, and gives the build a properly professional look. The frame is also given a mount so it can easily sit on a camera’s cold shoe fitting. Alternatively, a screw mount can also be used.

Good audio is absolutely key to making good content, and having quality mics is definitely what you need to achieve that. We’ve featured some other great DIY mic builds over the years, too. Video after the break. Continue reading “Camera-Mounted Stereo Mic Is Fluffy And Capable” →

Rib Cage Lamp Kicks It Up A Notch With Party Mode

October 1, 2022 by Donald Papp 8 Comments

We think [Michelle]’s sound-reactive rib cage lamp turned out great, and the photos and details around how it was made are equally fantastic. The lamp is made of carved and waxed wood, and inside is a bundle of LED lighting capable of a variety of different color palettes and patterns, including the ability to react to sound. Every rib cage should have a party mode, after all.

The LED strip is fashioned into an atom-like structure.

Turns out that designing good rib cage pieces is a bigger challenge than one might think. [Michelle]’s method was to use an anatomical 3D model as reference, tracing each piece so that it could be cut from a flat sheet of wood.

The resulting flat pieces then get assembled into a stack, with each rib pointed downward at a roughly 20 degree angle. This process is a neat hack in itself: instead of drilling holes all at exactly the same angle, [Michelle] simply made the holes twice the diameter of the steel rod they stack on. The result? The pieces angle downward on their own.

The LED lighting is itself a nice piece of work. The basic structure comes from soldered solid-core wire. The RGB LED strip gets wound around that, then reinforced with garden wire. The result is an atomic-looking structure that sits inside the rib cage. An ESP32 development board drives everything with the FastLED library.

Code for everything, including the sound-reactive worky bits, which rely on an INMP441 I²C microphone module is all available on GitHub. And if you want to make your own sound-reactive art, make sure to check out these arms as well.

Want to see the rib cage in action? A short demo video is embedded below that demonstrates the sound reactivity. Equally applicable to either party or relaxation modes, we think.

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Current Loop Extends Wired Microphones Past 1 Km

September 27, 2022 by Jenny List 22 Comments

A problem which beset early telephone engineers was that as the length of their lines increased, so did the distortion of whatever signal they wanted to transmit. This was corrected once they had gained an understanding of the capacitance and inductance of a long cable. The same effects hamper attempts to place microphones on long lines, and [Leo’s Bag of Tricks] has a solution for doing that using Cat5 cable. The application is audio surveillance, but we think the technique is useful enough to have application elsewhere.

The solution which you can see in the video below the break will be familiar to teletype aficionados who have encountered current loops, in that it creates an analogue current loop. There is a standing DC current in the tens of miliamperes, and this has the audio imposed upon it by an amplifier and shunt transistor. The audio can be easily retrieved using a pair of small transformers, leading to efficient transfer over as much of a kilometer of Cat5 cable. We’re guessing it’s not quite audiophile quality, but it’s useful to know that a current loop can be just as useful in the analogue domain as in the digital. If the subject interests you, we did a feature on them a few years ago.

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Machine Learning Gives Cats One More Way To Control Their Humans

August 26, 2022 by Dan Maloney 9 Comments

For those who choose to let their cats live a more or less free-range life, there are usually two choices. One, you can adopt the role of servant and run for the door whenever the cat wants to get back inside from their latest bird-murdering jaunt. Or two, install a cat door and let them come and go as they please, sometimes with a “present” for you in their mouth. Heads you win, tails you lose.

There’s another way, though: just let the cat ask to be let back in. That’s the approach that [Tennis Smith] took with this machine-learning kitty doorbell. It’s based on a Raspberry Pi 4, which lives inside the house, and a USB microphone that’s outside the front door. The Pi uses Tensorflow Lite to classify the sounds it picks up outside, and when one of those sounds fits the model of a cat’s meow, a message is dispatched to AWS Lambda. From there a text message is sent to alert [Tennis] that the cat is ready to come back in.

There’s a ton of useful information included in the repo for this project, including step-by-step instructions for getting Amazon Web Services working on the Pi. If you’re a dog person, fear not: changing from meows to barks is as simple as tweaking a single line of code. And if you’d rather not be at the beck and call of a cat but still want to avoid the evidence of a prey event on your carpet, machine learning can help with that too.

[via Tom’s Hardware]

A Lab-Grade Measurement Microphone For Not A Lot

June 8, 2022 by Jenny List 21 Comments

The quality of any measurement can only be as good as the instrument used to gather it, and for acoustic measurements, finding a good enough instrument can be surprisingly difficult. Commonly available microphones can be of good quality, but since they are invariably designed for speech or music, they need not have the flat or wide enough response and low noise figure demanded of an instrumentation microphone.

Microphones for measurement purposes can be had for a very large outlay, but here’s [Peter Riccardi] with a unit designed around an array of MEMS capsules that delivers comparable performance for a fraction of the cost.

The result is both an extremely interesting project for those of us with an interest in audio, and a thorough delve into some aspects of its design for those who are merely curious. It uses four capsules in an effort to cancel out induced electrical noise, and boasts some impressive comparative measurements when tested against a commercial measurement microphone. We could almost see ourselves building this project.

Interested in audio technology? Try our Know Audio series.