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.

Continue reading “Rib Cage Lamp Kicks It Up A Notch With Party Mode” →

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.

Continue reading “Current Loop Extends Wired Microphones Past 1 Km” →

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.

Vintage Pro Audio Hack Chat Gets In The Groove

May 27, 2022 by Tom Nardi 3 Comments

Despite the fact that we’ve been doing them for years now, it’s still hard to predict how a Hack Chat will go. There’s no question it will be an hour of interesting discussion of course, that much is a given. But the dynamics of the conversation can range from a rigid Q&A, which isn’t exactly unexpected when you’ve only got a limited amount of time with a subject matter expert, to a freewheeling hangout with a group of people who all happen to be interested in the same thing.

This week’s Vintage Pro Audio Hack Chat with Frank Olson definitely took the latter approach. The allotted hour flew by in a blink, with so many anecdotes and ideas flying back and forth that at times it was tricky to follow. But no worries, with the Chat transcript to pore over, we can make sure none of that accrued first-hand knowledge goes to waste.

So what did we learn during this Chat? Well, it probably won’t come as much of a surprise to find that those who have an opinion on audio gear tend to have a strong opinion on it. Folks were painting with some fairly broad brushes, with particular manufacturers and even whole fields of technology receiving a bit of good-natured ribbing. If your favorite brand or piece of gear gets a specific shout-out, try not to take it too personally — at the end of the day, most in the Chat seemed to agree that sound is so subjective that the right choice is more often than not whatever sounds best to you at the moment.

Which leads directly into Frank’s work with custom microphones. As a musician he knew the sound he was looking for better than anyone, so rather than spend the money on big-name gear, he prefers to build it himself. But the real hook here is their unique construction, with pieces that reimagine design concepts from mid-century commercial equipment using unexpected materials such as thin pieces of walnut cut with a vinyl cutter. Frank explains that the structure of the microphone isn’t as critical these days thanks to the availability of powerful neodymium magnets, which gives the builder more freedom in terms of materials and tools. He says the goal is to inspire others to try building gear from what’s available to them rather than assuming it won’t work because it’s unconventional.

We appreciate Frank, and everyone else, stopping by this week for such a lively and friendly discussion. Let’s be honest, a Chat specifically for folks who want to discuss concepts as personal and nebulous as how they perceive the warmth of sound could have gotten a little heated. But the fact that everyone was able to express their opinions or ask for advice constructively is a real credit to the community.

The Hack Chat is a weekly online chat session hosted by leading experts from all corners of the hardware hacking universe. It’s a great way for hackers connect in a fun and informal way, but if you can’t make it live, these overview posts as well as the transcripts posted to Hackaday.io make sure you don’t miss out.