Jimi Hendrix’s Analog Wizardry Explained

February 3, 1967 is a day that belongs in the annals of music history. It was the day Jimi Hendrix walked into London’s Olympic Studios to record a song using a new component. The song was “Purple Haze” and the component was the Octavia guitar pedal, created for Hendrix by audio engineer Roger Mayer. The pedal was a key part of a complex chain of analog elements responsible for the final sound, including the acoustics of the studio room itself. When they sent the tapes for remastering in the United States, the sounds were so new that they included an liner note explaining that the distortion at the end was not a malfunction but an intention. A few months later, Hendrix would deliver his legendary electric guitar performance at the Monterey International Pop Festival.

“Purple Haze” firmly established that an electric guitar can be used not only as a stringed instrument with built-in pickups for convenient sound amplification, but also as a full-fledged wave synthesizer whose output can be manipulated at will. Modern guitarists can reproduce Hendrix’s chain using separate plug-ins in digital audio workstation software, but the magic often disappears when everything is buffered and quantized. I wanted to know if a more systematic approach could do a better job and provide insight into how Hendrix created his revolutionary sound.

My fascination with Hendrix’s performance at Olympic Studios arose from the fact that there is a “Hendrix was an alien” narrative surrounding his musical innovation – that his music appeared more or less out of nowhere. I wanted to replace that narrative with an engineering-based, inspectable, repeatable narrative: plots, patterns, and a chain of signals from guitar to pedals that you can probe step by step.

Every effect pedal in the Hendrix chain has helped improve the electric guitar beyond its intrinsic limits. A selection of traces from analysis of the complete circuit show how the Fuzz Face transforms a sinusoidal signal from a string into an almost square wave; how the Octavia pedal inverts half of the input waveform to double its frequency; how the wah-wah pedal acts as a band-pass filter; and how the Uni-Vibe pedal introduces selective phase shifts to color the sound.James Provost/Rohan S. Puranik

Although I work primarily in the digital domain as an Edge Computing Architect in my day job, I knew that analog circuit simulations would be the key to moving forward.

My first step was to examine the challenges Hendrix was trying to overcome. Before the 1930s, guitars were too quiet for large ensembles. Electromagnetic sensors – spools of wire wrapped around magnets that detect the vibrations of metal strings – have solved the volume problem. But they left a new one: the envelopewhich specifies how the amplitude of a note varies when played on an instrument, starting with a rising initial attackfollowed by a fall rotand then any sustain of the note after that. Electric guitars attack hard, decay quickly, and don’t hold like bowed strings or organs. Early manufacturers attempted to modify the characteristics of the electric guitar by using hollow bodies fitted with magnetic pickups, but the instrument still barked more than it sang.

Hendrix’s mission was to reshape both the envelope and the sound of the electric guitar until it resembled a human voice. It addresses the constraints of the guitar by augmenting it. His solution was essentially a modular analog signal chain driven not by buttons but by hands, feet, gain staging, and physical movement in a feedback field.

Hendrix’s setups are well documented: set lists, studio diaries, and interviews with Mayer and Eddie Kramer, then chief engineer at Olympic Studios, fill in the details. The signal chain for “Purple Haze” consisted of a set of pedals – a Fuzz Face, an Octavia and a wah – plus a 100-watt Marshall amplifier, with the guitar and room acoustics closing a feedback loop that Hendrix tuned with his own body. Later, Hendrix would also incorporate a Uni-Vibe pedal for many of his songs. All pedals were commercial models except the Octavia, which Mayer built to produce a distorted signal an octave higher than its input.

Hendrix didn’t speak in decibels or ohms, but he collaborated with engineers who did.

I got the schematics for each of these and their accepted parameter ranges, and converted them into netlists that ngspice can process (ngpsice is an open source implementation of the Spice circuit analyzer). The Fuzz Face pedal came in two variations, using germanium or silicon transistors, so I created models for both. In my models, the Hendrix guitar pickups had a 6 kiloohm resistance and 2.5 Henry inductance with realistic cable capacitance.

I chained circuit simulations together using a script and produced data plots and sound samples with Python scripts. All ngspice files and other scripts are available in my GitHub repository at github.com/nahorov/Hendrix-Systems-Lab, along with instructions on how to reproduce my simulations.

What does Hendrix’s signal chain analysis tell us?

Plotting the signal at different points in the chain with different parameters reveals how Hendrix configured and manipulated the nonlinear complexities of the system as a whole to achieve his expressive goals.

Some highlights: First, the Fuzz Face is a two-transistor feedback amplifier that transforms a slight sine wave signal into an almost binary “fuzzy” output. Interesting behavior appears when the guitar volume is reduced. Since the pedal’s input impedance is very low (around 20 kΩ), the pickups interact directly with the pedal’s circuitry. Reducing the amplitude restores a sinusoidal shape, producing the famous “cleaning effect” that was a hallmark of Hendrix’s sound, where fuzz moves in and out at will as he plays.

The Jimi Hendrix Experience, (left to right) Mitch Mitchel, Jimi Hendrix, Noel ReddingFred W. McDarrah/Getty Images

Second, the Octavio pedal used a rectifier, which normally converts alternating current to direct current. Mayer realized that a rectifier effectively turns each dip in a waveform into a peak, thereby doubling the number of peaks per second. The result is an apparent doubling of frequency – a bloom of second harmonic content that the ear hears a bright octave above the fundamental.

Third, the wah-wah pedal is a band-pass filter: the frequency plots show the center frequency ranging from about 300 hertz to 2 kilohertz. Hendrix used it to make the guitar “speak” with vowel sounds, most iconically on “Voodoo Child (Slight Return).”

Fourth, the Uni-Vibe cascades four phase shift sections controlled by photoresistors. In circuit terms, it is a low-frequency oscillator modulating a variable-phase network; in musical terms, it is movement and air.

Eventually the whole chain became a closed loop by pushing the Marshall amplifier close to saturation, which among other things extends the sustain. In a reflective room, the guitar strings acoustically couple to the speakers: move a few centimeters and you switch from one stable feedback mode to another. To an engineer, this is a gain-controlled acoustic feedback system. For Hendrix, it was part of the instrument. He learned to adjust the oscillation based on distance and angle, shaping sirens, bombs, and harmonics as he walked on the edge of instability.

Hendrix didn’t speak in decibels or ohms, but he collaborated with engineers who did – Mayer and Kramer – and iterated quickly as a systems engineer. Reframing Hendrix as an engineer does not diminish the art. He explains how one person, in less than four years as a conductor, was able to pull the electric guitar toward its full potential by systematically augmenting the instrument’s flaws for maximum expression.

This article appears in the March 2026 print issue under the title “Jimi Hendrix, systems engineer.”