The Instant Phaser: A Timeless Classic Reborn - Eventide Audio

The Instant Phaser: A Timeless Classic Reborn

Whether you call it phasing or flanging, the “swoosh” sound is instantly recognizable and it’s hard to overstate the effect it’s had on the music of the past half century. The phaser has become a studio staple used both dramatically in songs like Van Halen’s “Ain’t Talkin’ Bout Love” or Led Zeppelin’s “Kashmir” and, more often, subtly to widen the sound of any instrument.

Birth of a Sonic Era

Have you ever wondered about what this eerie, unearthly effect is and how it came to be? Unlike reverberation, delay and pitch change—which occur naturally—phasing is doesn’t happen in the real world. Before the advent of tape recorders in the studio, the only time engineers used the word “phasing” was to describe gear wired out of phase or when multiple microphones are mixed. Phasing/flanging as a creative effect started with reel-to-reel tape machines.

Analog tape was THE major audio advance of the mid 20th century, making recording and playback easy encouraging all kinds of experimentation. With tape, audio could be delayed, its pitch changed and even reversed. In the 1950’s, visionaries like Pierre Schaeffer, Daphne Oram and Karlheinz Stockhausen used tape machines like an instrument to create time-based audio effects. And as early as 1952 Les Paul demonstrated a basic flanging effect. And, in 1959, an engineer at Gold Star Studios in LA, mixed the output of two tape machines running out sync which resulted in flanging’s first commercial use on the single “The Big Hurt” by Toni Fisher.

But it wasn’t until the mid ‘60s that the effect was used deliberately and became popular.

Imagine (cue sitar): Humphrey Osmond had just coined the term “psychedelic” to describe the sensation caused by hallucinogenic drugs such as LSD or psilocybin. It wasn’t long before those drugs entered the music scene both for listeners and creators alike. Hit radio “tripped out,” beaming the psychedelic sounds of bands like Moby Grape, Blues Magoos, The Electric Prunes, The Chocolate Watchband, The Seeds and 13th Floor Elevators into the brains of the ‘experienced’. And the new era demanded new sounds: lush echoes, reverse audio, wild panning, double tracking, bottomless reverb—anything to enhance that “psychedelic” headspace—but those tricks, even taken to the extreme weren’t enough – they weren’t new.

Musicians and engineers with two or more tape machines at their disposal experimented with combining the outputs of multiple machines and in the process discovered completely new effects. One in particular, flanging, could create a dreamy/swimming/dizzying sensation that fit right into the mellow slipstream of the 60s. In 1967 The Small Faces had an AM radio ‘hit’ with “Itchycoo Park” on which recording engineer George Chkiantz used the effect prominently.

At the time, a pair of college students in New York heard Itchycoo Park on AM radio and it left an impression. Just a few years later, those students became Eventide. Just sayin’.As an homage, a few Eventidians and their friends recently recorded a cover version. Here are some outtakes:

The How of Tape Flanging

Tape flanging is created by mixing the outputs of two reel-to-reel tape machines and by the engineer pressing a finger on the reel flange to slow down one of the machines. The changing delay between the two playbacks produces the effect.

The problem was, the process is complicated, time-consuming and expensive; requiring at least two reel-to-reel tape machines, patch cords – not to mention a very sensitive touch. It took practice and skill. As result flanging was used rarely and only by the more adventurous engineers and only at large studios. It took several major advances in electronics before it became practical to build a device that would make phasing possible by just turning a knob.

The Sound of Tape Flanging

Adding a signal to a delayed version of itself creates peaks and nulls in the combined signal’s spectrum because some frequencies will add (in-phase) and others subtract (out of phase). This results in a spectrum response that looks like a comb – engineers called the hollow sound “comb filtering.” The “swoosh” effect happens when the delay is varied. As the delay changes, the frequencies at which the output is reinforced and cancelled change—that is, the teeth of the comb get closer together or further apart. The sweeping hollow sound that we hear is called flanging.

Which is it? Phasing or Flanging

Historically, in the tape era, the terms “phasing” and “flanging” were used interchangeably to describe the tape-based effect. Afterall, there was only one effect, no matter what it was called. But things got a bit confused in 1972 when Eventide introduced its Instant Phaser.

A phaser can’t do exactly the same thing as tape flanging, because it is built using resistors and capacitors and resistors and capacitors can’t delay audio. A phaser uses a special type of analog filter called an ‘all pass’ filter. By wiring up a bunch of all pass filters you can get a ‘swooshing’ effect similar to, yet distinct from flanging – an effect with its own special sonic beauty.

(A few years later, the advent of things like bucket brigade ICs made the creation of a delay-based flanger possible, but that’s a story for another day.)

In order to distinguish this faux flanging effect from true tape flanging, Eventide (and others) used the term “phasing” and named their first rack mount effects box, the phaser, rather than the flanger. Some folks have never forgiven us.

The rest, as they say is history. With an electronic phaser, engineers could now print a phasing effect on as many tracks as they wanted, whenever they wanted, with no more hassle than turning a knob. No fuss, no muss. They could do it ‘instantly’ (nudge, nudge, wink, wink).

The Instant Phaser – Model PS101

The model number, PS101, says it all: Phase Shift 101. The Instant Phaser was a rack mount box of analog components with a Big Knob smack in the middle of its front panel. (Fun fact: It used light bulbs instead of LEDs.)

The big knob is one way to control the phase effect. Turning it manually ‘sweeps’ the effect. Or an LFO (Low Frequency Oscillator) can automatically sweep the phase. Or use the envelope (volume) of the audio to sweep the phase—perfect for drums! Or, use a ‘side chain’ signal to drive the sweep remotely with an external control voltage (CV). For instance, allow the drum signal to control the phasing effect for the bass. These are all control features that are standard now yet were innovative back in the day.

While studios originally purchased the Instant Phaser for its phasing effect, Eventide’s own User Manual suggested its capacity as a utility device. Eventide coined the phrase pseudo stereo to describe the Instant Phaser’s ability to spread a mono image across the stereo field. The PS101 is mono in, stereo out; the stereo outputs derived by means of phase manipulation. In other words, each output comes from a different analog phase shift filter and, as a result, the outputs are decorrelated. With the music industry moving from mono to stereo in the early ‘70s, the Instant Phaser’s ability to enhance the stereo image came in handy.

The Instant Phaser’s near-immediate acceptance by producers and engineers worldwide helped the fledgling Eventide grow. Within a few years, hundreds of these boxes were installed instudios worldwide. There was simply nothing else quite like it at the time. The Instant Phaser sound is printed on thousands of tracks to great effect from the subtle (even subconscious) to extreme. The classic swishy drum ‘wash’ on Led Zeppelin’s “Kashmir”? – that’s the Eventide Instant Phaser. Many studios installed a second box because engineers began using them to enhance the stereo image on lead guitars, vocals, hi hat, etc. For example, Herb Alpert used not one, but two Instant Phasers at legendary Henson Recording Studios.

Engineers like Steve Rosenthal and musicians like Todd Rundgren were known to use stacks of them:

Pictured: Todd Rundgren with a stack of Instant Phasers

Isao Tomita used the Instant Phaser on Snowflakes are Dancing and Kosmos. And it wasn’t just studios. The Instant Phaser, for some bands, became such an integral part of their sound that they had to take the boxes on tour. Zeppelin toured with an Instant Phaser in a rack as did Rush on their A Farewell to Kings tour.

The Plug-in: Instant Phaser Mk II

The Instant Phaser wasn’t cheap ($500 list in 1971 is equivalent to around $3,000 today), but it saved the costly studio time that tape flanging required, didn’t require manual dexterity and, once engineers discovered that it could be used to ‘fatten’ a stereo image, it became a must-have effect. With a limited manufacturing run that started 47 years ago, you’ll be hard-pressed to find an Instant Phaser to demo today. 

Instant Phaser Mk II Plug-in for AAX, VST and AU

Our original attempt to create a plug-in version of the phaser fell short. The trouble was that our initial efforts, based on a faulty interpretation of the historical documents, headed us off in the wrong direction and we just couldn’t get the sound right. And it’s bugged us for years!

So, we went back to square one. We’ve spent the last year faithfully replicating the sound of the Instant Phaser as a new plug-in, PS101 Mk II, and our ears tell us that we’ve finally succeeded. If you have access to a working vintage piece, please compare it to the plug-in and report back. Thanks.

With an updated interface and unique controls like Age, Mode switching, and sidechaining, there’s something for original Phaser users and newcomers alike.

Learn More

Instant Phaser PS101 
Instant Phaser MK II Plug-in