One non-negotiable aspect of electronic music is the need for powering the instruments. For portable instruments this calls for both an initial energy source such as a wall outlet, and a method of energy storage such as a battery. Both of these steps provide opportunities to consider materiality and environmental impact. The delicate nature of electronics is such that considering any one component in isolation is often impossible. Alterations to the power supply suggest additional changes to other parts of the instrument. In this project, I will present an electronic “ecosystem” made of three circuits that treat power as a germ from which to grow. By acknowledging historical relations and the materiality of electronic instruments, I will engage consciously in a “process of becoming” as laid out in Jose Martinez-Reyes’ framework for “Enviromateriality” of instruments (Martinez-Reyes).
Almost all commercially available synthesizers utilize wall outlet adapters or USB power. While it is possible to power these synthesizers using sustainably sourced AC power, a home solar rig for example, most users will be utilizing commercially available power grids. In the U.S., this means that only 20% of the needed power will come from renewable sources (Office of Energy Efficiency). One solution to this problem is integrating a renewable energy source directly into the device.
Oberlin alumni Peter Blasser’s “Tocante” line of instruments (released under the pseudonym Ciat-Lonbarde) is a great example of integrated renewable charging in musical instruments (Blasser 130). These devices utilize a solar panel, nickel metal hydride battery, and touch detector circuit which only powers on the synthesizers when they are being played. Because the instruments have batteries, they can be played after charging at night or indoors.
From left to right: unknown Tocante backside, “Thyris”, “Bistab”, “Phashi” (Ciat-Lonbarde)
While elegant, the use of nickel metal hydride batteries in the Tocantes produces a limiting factor in terms of maintenance and lifetime of the instruments, an important consideration for reducing waste and environmental costs of manufacturing. Energizer estimates the lifetime of these batteries as being less than five years, significantly shorter than the lifetime of the passive components that make up the majority of the circuitry (Energizer). For example, Vishay film capacitors are rated for a million hours of active operation under optimal conditions, or about 114 years of straight usage (Vishay). Given that one accepts some amount of drifting of component values, which should not be as critical in a synthesizer as it might be in something like aerospace or medical equipment, resistors have similarly good longevity (Vishay Drift Calculation). With the exception of electrolytic capacitors, which can be avoided in many use cases, the battery would be the first component to fail (XP Power). Additionally, nickel is a “conflict mineral”, meaning that its supply chain is often linked with human rights abuses (SOMO).
The other type of commonly available rechargeable battery is made from lithium and is even less satisfactory than nickel metal hydride. Lithium batteries only last about two years, and can be recharged far fewer times than nickel metal hydride (Newark). Lithium, like nickel, is a conflict mineral. It also has problematic storage requirements which frequently result in cells going bad before being used to their full potential, sometimes also causing fires.
Blasser, as well as other instrument makers including Daniel Fishkin, have explored directly powering instruments with solar panels (Fishkin). These battery-less instruments are called solar sounders and function analogously to windchimes, producing sound only when directly excited by the environment (sunlight in this case rather than wind). This approach is appealing because it removes the need for energy storage altogether, but limits use of the instruments to settings where sunlight is available and makes it necessary to ration power usage carefully in the circuit design.
Supercapacitors are an alternative type of energy storage that have the potential to replace batteries in some applications. Supercapacitors can have a lifetime of up to 100 years under correct operating conditions, and can sustain hundreds of thousands of recharge cycles (Hahn et al.). Unfortunately, supercapacitors are both far less energy-dense and much more expensive than batteries. For example, a standard 1200maH lithium 9V battery stores 8 times as much energy as two 100F 2.7V supercapacitors combined. One could purchase 8 of the former for the same price as one of the latter. Supercapacitors also require significant external circuitry to provide a constant output voltage (a requirement for traditional circuits), further elevating costs. These disadvantages may be worth overlooking for the sake of reduced environmental footprint and can be partially mitigated by choices elsewhere in the instrument as I will discuss later.
For this project, I attempted to design a solar supercapacitor charger with built-in 5V and 9V output capabilities, low-light charging conditions, and usb-power for cloudy days. Unfortunately due to my inexperience with boost converter technology, the circuit does not function fully as intended. The 5V output and low-light converter both make use of the MCP1640 boost converter, and neither functioned on my build. The 9V output instead uses the LM2623 and does function mostly properly, although sometimes drops below 9V depending on the circuits connected to it. Fortunately, I was still able to power the other circuits I designed using this energy source, although the performance is affected relative to battery-powered operation (reduced volume, lower pitch with less activity). I plan to examine this circuit more closely to see if I can get it working properly in the future. I would also like to experiment with direct solar panel power.
Supercapacitors, solar panels, and malfunctioning charger circuitry 🙁
It’s possible to accommodate the low power density of supercapacitors by designing circuits that consume low amounts of power so that a reasonable use time can be achieved despite reduced energy storage. There is a pre-existing tradition of DIY synthesizers called “Lunettas” (after Stanley Lunetta), which make use of a very low-power family of components called complementary metal oxide semiconductors (CMOS) (electromusic). CMOS chips are widely available, affordable, and easy to design around. One common CMOS chip, the CD4069, consumes less than a microwatt in a 9-volt circuit compared with up to 500 watts consumed by a large computer or up to several hundred watts consumed by a guitar amplifier (Texas Instruments, Marsh). Due to their low power usage, a marriage of Lunetta synthesizers and supercapacitors may be fruitful.
One common CMOS circuit is the ring oscillator, which is made up of an odd number of inverters in a ring. Each inverter produces a high voltage at its output when it has a low voltage at its input and vice versa. This circuit produces something like a paradox, where if one begins with a low voltage at any particular node, one finds that the same node must be at a high voltage according to the preceding inverter. What happens in reality is that the inverters cannot invert instantaneously, and so flip back and forth between states yielding an oscillating signal. Any oscillating signal containing frequencies in the range 20hz-20khz can be thought of as a sound wave, and so the ring oscillator can be used for musical purposes.
Ring oscillator “paradox”
A 2019 paper showcased the potential of modified CMOS ring oscillators to produce “a multitude of qualitatively-different dynamical behaviors”, which is highly suggestive of varied musical potential (Minati et al.). Some of these behaviors were described by the researchers as “reminiscent of action potentials” or electric signals in the brain. The circuit structure was inspired by breeding patterns of some species of cicada, which live for differing prime numbers of years to minimize competition from synchronization of breeding seasons. Following this use of prime numbers, the researchers connected ring oscillators of 3, 5, and 7 inverters together. Their circuit also utilizes a technique called current starvation, where the resistance between the power supply and a circuit is deliberately increased. This causes unpredictable behavior as different components of a circuit “compete” for power, and is a powerful technique (no pun intended) for producing more complicated behavior without increasing power consumption. Current starvation is frequently utilized by musicians to modify the sound of guitar pedals and synthesizers (reddit).
Simple signals with prime number frequency relations combine to create complicated signals. This principle applies equally to cicadas and ring oscillators. (5G Technology World)
The cicada-inspired ring oscillators are one example of how biological mimesis can inform simple and elegant designs for producing surprisingly varied behavior. This is reminiscent of the biological mimesis found in many indigenous cultures. In Ted Levin’s Where Rivers and Mountains Sing: Sound and Spirits in Tuva Tolya Kuular, an indigenous musician, explains how Tuvan singers may sing “like a river, or like the wind on a mountain, or like a bird” (Levin). By turning to non-human forces for inspiration, the instrument maker or musician can access ways of being that have had a longer history than any human technology. Remarkable mechanisms like that of the cicada’s prime lifespan or the unpredictable whistling of a river may be the impetus for ecological innovation.
The complicated dynamics of CMOS circuits provide an opportunity for listening in another sense as well. The researchers in the previously mentioned paper proved that these circuits are capable of producing chaos. Chaos in mathematics describes systems that are highly sensitive to initial conditions. In other words, if two identical copies of a chaotic system are placed under nearly identical circumstances, they will eventually still diverge in path. What this means effectively is that how the system will behave in the future cannot be predicted, as very similar present states will produce wildly different future states. In a musical context, chaos forces musicians into a dialogue with the instruments and their surroundings, because the behavior of the system is constantly in flux. One cannot rely on memory, muscle or otherwise, to produce even remotely similar musical output. Instead, musicians must listen to their instruments and constantly adjust their performance, reacting to the instrument as much as the instrument reacts to them. This process of listening, much like the practice of listening to rivers (which are also chaotic in the mathematical sense), provides an opportunity to cultivate musical sensitivity and awareness (Meridian International Research).
A chaotic system, where each pendulum began nearly overlapping. I suggest watching the video version (wikimedia).
For this project, I made my own adjustments to a ring oscillator circuit. Inspired by the cicada circuit, I implemented a current starve. Using a field effect transistor, I was able to control the amount of current starvation with a voltage of my choosing rather than having the amount be fixed. This way, the circuit’s state itself can control how readily it can access current, which creates a feedback loop of behavior. I added feedback around each inverter, which has the effect of making the transition from high to low states more gradual. I also added a CMOS analog switch, which adds or removes connections between assorted parts of the circuit depending on the state of other parts of the circuit. While I lack the mathematical tools to rigorously prove that the circuit demonstrates chaos in a strict sense, its behavior sounds chaotic as it switches between various patterns or near-repetitions unpredictably. In his Pulitzer prize winning book on cognition Gödel Escher Bach, Douglas Hofstadter coined the term “strange loops” to describe the “self-modifying” feedback loops across “levels of abstraction” that he predicted to be ingrained in the structure of chaotic and cognitive systems (Hofstadter 684). By implementing feedback from the produced signals to the power supply, and from produced signals to the routing of the system producing them, the ingredients for strange loops and thus neuromorphic or chaotic behavior are in place.
Modified ring oscillator circuit
An aspect of electronic instrument design that I have so far neglected to talk about is the problem of how to transform an electrical signal into audible air pressure waves. Given the requirements of this project to be low power, portable, and complement the aesthetic goals of the project by encouraging listening, I chose to design a portable amplifier connected to a surface transducer, which is similar to a speaker but without a paper membrane with which to push air. Surface transducers can be attached to many objects, vibrating the entire object and using it as a means to project sound into the air. The amplifier circuit functions, although it consumes more power than I would like and has a bit of trouble running properly from the supercapacitor. I plan to explore other amplifier topologies in order to reduce the power consumption.
Amplifier and surface transducer
The surface transducer, like the ring oscillator, encourages the user to practice listening and awareness in their music-making. Instead of aiming for pure reproduction of signal, the transducer draws attention to the resonances of the object that it excites and provides a way of knowing said object through sound. This design celebrates the interactions between sound and its material surroundings rather than attempting to erase them through homogenization, bringing to the surface the relations and possibilities of knowing captured by Steven Feld’s formulation of “Acoustemology”, or knowing through sound (Feld).
The trio of circuits presented above function as a proof of concept for musical circuit design which takes environmental principles as foundational, and considers the way in which components of an instrument relate to each other, themselves, the musicians, and other parts of the material world. Although there are some technical challenges to overcome, with continued work the “power first” relational process laid out in this project has the potential to yield a sustainable and conscious family of electronic instruments.
Appendix: Sound Examples
transducer amplifier and ring oscillator powered by a sun charged supercapacitor
transducer amplifier and ring oscillator powered with batteries. This video showcases the ring oscillator spontaneously changing patterns without being interacted with.
microphone plugged into the ring oscillator. Experimenting with humming/singing with the synthesizer. Also battery powered.
Works Cited
Martinez-Reyes Jose. 2015. “Mahogany Intertwined: Enviromateriality between Mexico, Fiji, and the Gibson Les Paul.” Journal of Material Culture 1-17.
“Renewable Energy.” Office of Energy Efficiency and Renewable Energy, https://www.energy.gov/eere/renewable-energy#:~:text=modernize%20the%20grid.-,Renewable%20Energy%20in%20the%20United%20States,that%20percentage%20continues%20to%20grow.
Blasser, Peter. 2015. “STORES AT THE MALL.” https://doi.org/10.14418/wes01.2.84
Blasser, Peter. “Tocante.” Ciat-Lonbarde, https://www.ciat-lonbarde.net/tocante/index.html
Energizer. “Nickel Metal Hydride (NiMH) Handbook and Application Manual.” Energizer, https://data.energizer.com/pdfs/nickelmetalhydride_appman.pdf
Vishay. “Did you know? Life expectancy for DC-Link Film Capacitors.” Vishay, https://www.vishay.com/docs/48164/_did-you-know_dclink_vmn-ms7369.pdf
Vishay. “Drift Calculation for Thin Film Resistors.” Vishay, https://www.vishay.com/docs/28809/driftcalculation.pdf
XP Power. “Electrolytic capacitors determine the lifetime of a power supply.” XP Power, https://www.xppower.com/resources/blog/electrolytic-capacitor-lifetime-in-power-supplies#:~:text=Manufacturers%20of%20electrolytic%20capacitors%20specify,to%2010%2C000%20hours%20or%20more.
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http://dfiction.com/solar-sounders/
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Marsh, Jacob. “How many watts does a computer use?.” energysage, https://www.energysage.com/electricity/house-watts/how-many-watts-does-a-computer-use/
Minati, Ludovico et al. “Current-Starved Cross-Coupled CMOS Inverter Rings as Versatile Generators of Chaotic and Neural-Like Dynamics Over Multiple Frequency Decades.” IEEE Access 7 (2019): 54638-54657.
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Tokyo institute of technology. “Creating Integrated Circuits That Can Generate Chaotic Signals.” 5G technology world, https://www.5gtechnologyworld.com/creating-integrated-circuits-that-can-generate-chaotic-signals/
Levin, Ted. 2006. Excerpts. Where Rivers and Mountains Sing: Sound, Music, and Nomadism in Tuva and Beyond. Bloomington: Indiana University Press. “The World is Alive with the Music of Sound.” 26-40, “Sound Mimesis and Spiritual Landscape,” 88-90, 98
Meridian international research. 2003. “Observations on the application of chaos theory to fluid mechanics.” Meridian international research, http://www.meridian-int-res.com/Aeronautics/Chaos.pdf
Wikimedia commons. “Demonstrating chaos with a double pendulum.” Wikimedia commons, https://upload.wikimedia.org/wikipedia/commons/e/e3/Demonstrating_Chaos_with_a_Double_Pendulum.gif
Hofstadter, Douglas. “Gödel Escher Bach: an eternal golden braid.” physix fan, https://www.physixfan.com/wp-content/files/GEBen.pdf
Feld, Steve. 2015. “Acoustemology” Keywords in Sound Duke Univ. Press, ed. David Novak (OC ‘97) and Matt Sakakeeny. 12-21
