Musical Hacks

1490 Articles

Know Audio: It All Depends On The DAC

October 20, 2021 by 29 Comments

Our trip through the world of audio technology has taken us step-by step from your ears into a typical home Hi-Fi system. We’ve seen the speakers and the amplifier, now it’s time to take a look at what feeds that amplifier.

Here, we encounter the first digital component in our journey outwards from the ear, the Digital to Analogue Converter, or DAC. This circuit, which you’ll find as an integrated circuit, takes the digital information and turns it into the analogue voltage required by the amplifier.

There are many standards for digital audio, but in this context that used by the CD is most common. CDs sample audio at 44.1 kHz 16 bit, which is to say they express the level as a 16-bit number 44100 times per second for each of the stereo channels. There’s an electrical standard called i2s for communicating this data, consisting of a serial data line, a clock line, and an LRclock line that indicates whether the current data is for the left or the right channel. We covered i2s in detail back in 2019, and should you peer into almost any consumer digital audio product you’ll find it somewhere. Continue reading “Know Audio: It All Depends On The DAC” →

The Quadrivium EnsembleBot Is A Labour Of Love

October 19, 2021 by 5 Comments

The Quadrivium EnsembleBot project is a mashup between old school musical instruments and the modern MIDI controlled world. Built by a small team over several years, these hand crafted instruments look and sound really nice.

The electronics side of things is taken care of with a pile of Arduinos and off-the-shelf modules, but that doesn’t mean the design isn’t well thought through, if a little more complicated than it could be in places. Control is taken care of with a PC sending commands over the USB to an Arduino 2560. This first Arduino is referred to as the Master Controller and has the immediate job of driving the percussive instruments as well as other instruments that are struck with simple solenoids. All these inductive loads are switched via opto-isolators to keep any noise generated by switching away from the microcontroller. A chain of four sixteen-channel GPIO expander modules are hung off the I2C bus to give even more opto-isolated outputs, as even the Arduino 2560 doesn’t quite have enough GPIO pins available. The are a number of instruments that have more complex control requirements, and these are connected to dedicated slave Arduinos via an SPI-to-CAN module. These are in various states of development, which we’ll be keeping our beady eyes on.

One of the more complex instruments is the PipeDream61 which is their second attempt to build a robotic pipe organ. This is powered by a Teensy, as they considered the Arduino to be a little too tight on resources. This organ has a temperature controller using an ATTiny85, in order to further relieve the main controller of such a burden and simplify the development a little.

Another interesting instrument is Robro, which is a robotic resophonic guitar which as they say is still work in progress despite how long they have been trying to get it to work. There’s clearly a fair bit of control complexity here, which is why it is taking so much fiddling (heh!) to get it work.

This project is by no means unique, lately we’ve covered controlling a church organ with MIDI, as well as a neat Arduino Orchestra, but the EnsembleBot is just so much more.

Continue reading “The Quadrivium EnsembleBot Is A Labour Of Love” →

Nicolas Bras and his homemade musical instruments

Hacked Set Of Instruments Saves Musician’s Gigs

October 8, 2021 by 19 Comments

Most of the horror stories you hear about air travel seem to center around luggage. Airlines do an admirable job of getting people safely to their destinations, but checked baggage is a bit of a crapshoot — it could be there when you land, it could end up taking the scenic route, or it could just plain disappear. That’s bad enough when it contains your clothes, but when it contains your livelihood? Talk about stress!

This was the position musician [Nicolas Bras] found himself in after a recent trip. [Nicolas] was heading for a gig, but thanks to Brussels Airlines, his collection of musical instruments went somewhere else. There was nothing he could do to salvage that evening’s gig, but he needed to think about later engagements. Thankfully, [Nicolas] specializes in DIY musical instruments, made mostly with PVC tubes and salvaged parts from commercial instruments, so the solution to his problem was completely in his hands.

Fair warning to musical instrument aficionados — harvest the neck from a broken ukelele is pretty gruesome stuff. Attached to a piece of pallet wood and equipped with piezo pickups, the neck became part of a bizarre yet fascinating hybrid string instrument. A selection of improvised wind instruments came next, made from PVC pipes and sounding equally amazing; we especially liked the bass chromojara, sort of a flute with a didgeridoo sound to it. The bicycle pump beatbox was genius too, and really showed that music is less about the fanciness of your gear and more about the desire — and talent — to make it with whatever comes to hand.

Here’s hoping that [Nicolas] is eventually reunited with his gear, but hats off to him in the meantime for hacking up replacements. And if he looks familiar, that’s because we’ve seen some of his work before, like his sympathetic nail violin and “Popcorn” played on PVC pipes.

Continue reading “Hacked Set Of Instruments Saves Musician’s Gigs” →

Demonstrating ThermoAcoustics With The Rijke Tube

October 5, 2021 by 20 Comments

The Rijke tube is a very simple device that demonstrates the principle of thermoacoustics quite clearly. Construction is quite straightforward, simply place a metal gauze at the bottom end of a tube, approximately one quarter of the way up, apply a source of heat to the gauze, and instant sound. The heat produces convection, setting up a longitudinal standing wave. This is due to air passing over the hot gauze, suddenly expanding and causing a pressure change, which rushes out the tube. Next, the airflow cools and slows, and air starts to head back into the tube, and the cycle repeats. Adjusting the tube length by slipping a sleeve over it, adjusts the pitch of the note, simply because the air has a different distance to travel. If there is a flame aimed at the gauze from below, the sound will stop since the air is already hot when it hits the hot gauze, no pressure change occurs, and no oscillation.

As [Keith], the reader who sent in the tip, suggests it would be fun to attach a servo to a sleeve on the tube, build multiple units and hang the whole thing off a MIDI controller. This could make for some fun times, and we have to agree. The problem of keeping the gauze hot could be solved in a number of ways, direct resistive heating could work, but maybe inductive heating would be cleaner?

Now, we can’t find an instrument which works in this manner, which sounds like a hack in the making for someone out there so inclined.

There have been a few fire-orientated musical devices over the years, such as this Rijke Tube Organ, various variants on the pyrophone, including this neat one performing with a tesla coil, and while we’re talking about music fire, howsabout a two dimensional rubens’ tube variant?

Continue reading “Demonstrating ThermoAcoustics With The Rijke Tube” →

This Audio Mixer Is A Eurorack

October 4, 2021 by 14 Comments

Music making and DJing have both become arts predominantly pursued in a computer, as the mighty USB interface has subsumed audio, MIDI, and even DJ turntable interface controllers. There was a time though when an indispensable part of any aspiring performer’s equipment would have been an analog mixer, a device for buffering and combining multiple analog audio signals into a single whole. A mixer is still a useful device though, and [Sam Kent] has produced a very nice one that takes the form of a set of Eurorack modules made from PCB material. There are two types of modules, the main channel module which you can think of as the master module, and a series of isolator modules that handle the individual inputs.

Mixer preferences are as individual as each user, so for example where we’d expect sliders he’s used rotary potentiometers, and for us placing the master channel on the left-hand side is unfamiliar. But that’s the beauty of a modular design, there’s nothing to stop anyone building one of these to simply configure it as they wish. We notice that for a mixer described as for DJs there’s no RIAA preamp for the turntable fans, but it’s not impossible to fix with an off-board preamp. Otherwise, we like it and have a sudden hankering for it to be 1992 again with a pair of Technics SL1200s and a room full of people.

Designing a mixer, even a simple one, isn’t easy. Our own [Lewin Day] wrote a retrospective of his experiences with one.

Laser Theremin Turns Your Hand Swooshes Into Music

October 3, 2021 by 10 Comments

In a world where smartphones have commoditized precision MEMS Sensors, the stage is set to reimagine clusters of these sensors as something totally different. That’s exactly what [chronopoulos] did, taking four proximity sensors and turning them into a custom gesture input sensor for sound generation. The result is Quadrant, a repurposable human-interface device that proves to be well-posed at detecting hand gestures and turning them into music.

At its core, Quadrant is a human interface device built around an STM32F0 and four VL6180X time-of-flight proximity sensors. The idea is to stream the measured distance data over as fast as possible from the device side and then transform it into musical interactions on the PC side. Computing distance takes some time, though, so [chronopoulos] does a pipelined read of the array to stream the data into the PC over USB at a respectable 30 Hz.

With the data collected on the PC side, there’s a spread of interactions that are possible. Want a laser harp? No problem, as [chronopoulos] shows how you can “pluck” the virtual strings. How about an orientation sensor? Simply spread your hand over the array and change the angle. Finally, four sensors will also let you detect sweeping gestures that pass over the array, like the swoosh of your hand from one side to the other. To get a sense of these interactions, jump to the video demos at the 2:15 mark after the break.

If you’re curious to dig into the project’s inner workings, [chronopoulos] has kindly put the firmware, schematics, and layout files on Github with a generous MIT License. He’s even released a companion paper [PDF] that details the math behind detecting these gestures. And finally, if you just want to cut to the chase and make music of your own, you can actually snag this one on Tindie too.

MEMs sensors are living a great second life outside our phones these days, and this project is another testament to the richness they offer for new project ideas. For more MEMs-sensor-based projects, have a look at this self-balancing robot and magic wand.

Continue reading “Laser Theremin Turns Your Hand Swooshes Into Music” →

MicroSynth, the business card-sized synthesizer

MicroSynth Mixes All-Analog Fun With A Little Business

September 30, 2021 by 14 Comments

While [MicroKits]’ MicroSynth is an all-analog synthesizer that fits on a business card-sized PCB, and he actually does use it to break the ice in business meetings, that’s not really the idea behind this project. Rather, [MicroKits] is keen to get people playing with synths, and what better way than a synth you can build yourself?

There was an ulterior motive behind this project, too: prototyping circuits for a more complete synthesizer. Thus, the design is purposely very simple — no microcontrollers, no logic chips, and not even a 555 to be found. It doesn’t even have buttons; instead, the one-octave keyboard just has interdigitated traces that are bridged by the player’s fingers, forming resistive touchpads. The keyboard interface circuit is clever, too — [MicroKits] uses a pair of op-amps to convert the linear change in resistance across the keyboard to a nearly exponential voltage to drive the synth’s voltage-controlled oscillator (VCO). The video below shows what it can do.

We love projects like these because they show what can be accomplished strictly using analog circuits. We don’t have any problem with other synth designs, mind you — this 555-based dub siren we featured recently was great, too. Continue reading “MicroSynth Mixes All-Analog Fun With A Little Business” →