From Phasing to Flanging - Eventide Audio

From Phasing to Flanging

Phased Out

In 1971, the Instant Phaser’s introduction rocked plenty of boats. With classic features like oscillator-controlled phasing and manual phasing, as well as innovations like the Envelope Follower and remote (CV) control, the Instant Phaser did phasing unlike any other box of its time. It even had two outputs with decorrelated phase shifts, which meant that the Instant Phaser was able to create instant pseudo-stereo – a valuable tool in the studio when the world of recording was quickly moving away from mono.

Despite being designed as an affordable alternative to the tape effect called phasing/flanging, the Instant Phaser carved out a space entirely for itself as a distinct, unique effect, able to do things that could not be accomplished with tape. Studios that could afford to buy several tape machines and employ the most skilled tape-flanging engineers, like Henson Recording Studios run by Herb Alpert, still had to have at least one Instant Phaser for that invaluable instant pseudo-stereo. Herb bought two.

The Instant Phaser was wildly popular: it was an excellent tool, a new sound effect, and one of the first electronic effect boxes ever made. But the engineers at Eventide had the itch. They had set out to make a flanging box, and the Instant Phaser wasn’t exactly that – so, back to the drawing board.

Far-Out Flanging, Man  

The flanging effect comes from playing two copies of the same recording, summing them and manipulating the playback speed on one to cause a varying delay. This creates a phase cancellation relationship between the two recordings, creating the classic ‘swoosh’ effect. As you manipulate the delay on one recording, it changes the frequencies at which the signal is reinforced and the frequencies which cancel. This is called “comb filtering”: on a spectrum analyzer, the uncancelled frequencies appear to look like the teeth of a comb.

In the ‘60s, this was accomplished by rigging up two tape machines and starting them at the same time, with their outputs sent to a third tape machine. The engineer would then press a finger on the tape flange of one of the machines, causing a very slight delay between the two machines. The third machine would sum these inputs, and voila – tape flanging.

To get this effect on one song for even a short period of time, however, could require hours of studio time. And at a major recording studio that could afford three tape machines and a skilled engineer, that kind of studio time was not cheap.

The Instant Phaser was created to save time and expense. You could plug in the recording, rig up any controls you liked, and print it to tape – you could do it “instantly”. The issue with phasing boxes was that, despite their riveting, peculiar sound, no hardware phaser could sound as “deep” as dragging the flange on a tape machine. Why? The Instant Phaser used a series of analog all-pass filters to create the classic ‘swoosh’ effect. They sounded great, but they could only create a few ‘combs’ in the audio spectrum.

(The “deep” sound of flanging comes from extra nulls in the frequency response from the delayed, out-of-phase signal colliding in variable speed with the original input, as well as the longer period before transients are nulled out of the final sonic result.)

So why not replace the all-pass filters with a variable delay line, and run that against the input signal? This was exactly the thinking of the engineers back in 1971, before the Instant Phaser even reached the production lines.

A Short Delay…

Delay was a complicated topic in 1971. All delay had been done using microphone placement or using analog tape, because doing it inside the box was brand new. Not to mention, it was quite expensive – the only box-based delay line available at the time was the $3,800 Eventide 1745 Digital Delay Line, about $23,300 in today’s dollars. The 1745 DDL had quite a few professional uses, ADT (automatic double tracking), plate reverb pre-delay and sound reinforcement for PAs, which justified its high price tag; but to charge $20,000 for a Flanger box, when that kind of money could get you a tape machine or two? No dice.

Plus flanging doesn’t require the delay length of the 1745 which was a whopping 200 ms. Not a lot in today’s delay world of 2,000 ms of delay as a standard, but an overwhelming amount of delay in 1971. The Instant Flanger only needed about 20 ms of delay in order to produce that magic comb filter effect.

So, why not divide that $3,800 price tag by ten and only provide 20 ms of delay? It didn’t exactly work like that, folks… Most of the expense from a digital shift register based DDL came from the digital converters. These were the days before commercial A to D chips and so any digital approach required designing custom A to D and D to A converters, lots of analog pre and post processing and a fistfull of digital circuitry. In fact, the version of the DDL 1745 with half the amount of delay time (100 ms) was only $500 cheaper, so the expense of 20 ms digital delay back in the mid 70’s would top $10,000 of today’s dollars. Still no dice.

From Pg. 20 of the original Instant Flanger manual – they really did try everything!

So, Eventide engineers made the logical choice of building their first effects box using all-pass filters. These all-pass filters preserved the frequency content of the original signal, but altered the phase at specific frequency points across a spectrum. No delay in that circuit, but you still got that “swoosh” effect, and it still sounded pretty damn cool. And the Instant Phaser was still a smash hit, with controls that knocked tape flanging out of the park.

That certainly wasn’t the end of the story, though…

Instant Flanger, without Instant Angst

Five years later, the landscape of audio was changing quickly. With instruments being developed like the Minimoog and the Linn Drum Machine, the advent of the car stereo system, and cassette tape coming back strong with Dolby Hi-Fi, the music industry was booming. Plenty of money was going into the development of consumer-grade audio technology. One such legendary development, still wildly popular today, was the bucket brigade delay chip.

Licensed by Matsushita (now Panasonic) in the mid-70s, the Bucket Brigade Delay chip was revolutionary. You’ve probably heard of these from the “cool” delay pedals; now coveted for that smokey analog delay sound, BBD chips were designed as an entirely analog, in-the-box alternative to analog tape delay and digital shift register delay.

The bucket brigade chip is an IC (integrated circuit). It contains thousands of capacitors and transistors (switches), wired up to sample the analog voltage at a high rate and pass the analog charge along a string of buckets like a fire department “bucket brigade”. At each capacitor step, a charge is held until a transistor switches it along to the next capacitor at a rate determined by an external clock. The faster the clock, the shorter the delay. The signal is low-pass filtered in order to avoid aliasing, which gives bucket brigade chips the classic fade-out delay sound that analog pedal fans know and love.

When this technology became available, the engineers at Eventide immediately saw a major opportunity. BBD chips allowed audio to be delayed variably for a fraction of the price of a digital delay or multiple tape machines. That affordable delay line was finally here – their initial plans for the Instant Phaser-as-Flanger could finally be realized! Using a delay instead of an all-pass filter would exactly recreate that deep dragged-flange sound, since a delayed copy of a signal played against the original signal would create a comb filter. Hence, the Eventide Instant Flanger was born.

Like the Instant Phaser, it quickly found a home in studios and band rigs worldwide. When Led Zeppelin performed “Kashmir” live, they used the Instant Flanger. (The Instant Phaser was on the studio recording, but the Flanger nailed it live.) Stanley Clarke used it across multiple albums. Isao Tomita also used the Instant Flanger on Kosmos and The Bermuda Triangle. Frank Marino toured with the Instant Flanger. And Jonathan Wilson still uses one today.

Without further ado, the Instant Flanger:

Out of Control

The Instant Flanger was, and still is, unlike any Flanging box on the market. The BBD chips it employed gave it a unique color and warmth, but the real magic in this box came from the unparalleled methods of controlling the flanging.

  • Bounce: This control moved the flanging back and forth by a diminishing amount for each swing, mimicking the “hunting” effect created by a tape servo motor changing speed. In other words, tape wobble.
  • Depth: This was a sort of “mix” control for the Flanging. With a Main output and an Auxiliary output on the back of the Flanger, both receive delayed signal at full amplitude at all times. But, without the presence of the original signal, one hears pitch change via the effect known as Doppler Shift. Depth controlled how much of the original signal was sent to each output, with the clockwise and counterclockwise settings determining whether the dry signal is added in or out of phase with the delayed signal on each output. The amount of dry signal introduced determines  the “depth” of flanging.
  • Rate: Classic LFO-style swept flanging, with the waveform period ranging from 20 seconds to 50 milliseconds.
  • Big Knob: Manual flanging control. Turn the knob to manually sweep the flanging or dial in a fixed ‘phase’ sound.
  • Envelope Follower: The signal level drives the flanging sweep.

The Instant Flanger’s controls were built to convince even tape-flanging capable studios that they needed one of these – it just did more in every department, and it was worlds easier to use.

But it didn’t stop there! It could be used for more than the flanging effect:

  • Pseudo-Stereo: With phase-decorrelated Main and Aux outputs, you could send them to a Left and Right channel for Instant Stereo (as used on Cyndi Lauper’s “Time After Time” to widen the stereo image.)
  • Doubling/Automatic Double Tracking (ADT): The Instant Flanger provided some seriously fat doubling with its built-in delay. With the Depth knob set to twelve o’clock, there is no contribution of the dry signal so the outputs are pure delay. This feature was considered a “secret weapon” by several record engineers/producers.
  • Doppler: With the Depth knob set to twelve o’clock, the pure delay could be swept a Doppler effect. This was heavily leaned on by producers everywhere. Even just a tad of swept delay can add some movement to a static guitar riff.
  • Feedback Reduction: Shifting the output frequency from the input by a few Hertz can prevent signal buildup on one resonant frequency without drastically changing the sound. You could achieve this by rigging a small Doppler shift with the Depth knob set to the middle, with the LFO constantly performing a slow sweep.
  • Feedback (!): Some users took a drill to the Instant Flanger’s front panel to add an extra potentiometer for feeding the output back to the input to create a feedback loop. Given the unique circuitry and control set of the Flanger, this was no mere delay-pedal feedback, but a ringing, clanging feedback whirlwind. A coveted modification.
  • 60 Hz Hum Reduction: When cancelling 60 Hz ground hum with a 60 Hz phase-inverted sine tone, the harmonics would still be present. Using the comb filter produced by the Flanger, you could nab all those harmonics as well as the fundamental, making the Flanger a very effective ground-hum eliminator.
Notice still applies!

The Eventide Legacy

To this day, the Instant Flanger and the Instant Phaser have a sound unlike any other flanger or phaser, hardware and software alike. Over the past couple of months, we’ve reached out to modern recording studios across the globe that list either an Instant Flanger or Phaser in their inventory. Many responded, saying that they frequently use them on their mixes for their unique character.

Considering that the manufacturing run of hardware Instant Phasers and Instant Flangers was limited, we’ve tried to recreate the sound of the Instant Flanger and Instant Phaser in older versions of our Anthology plugin bundle. The problem was, we just couldn’t get the sound right! That’s why we’ve spent the past year faithfully replicating them, and we believe we’ve finally succeeded. Introducing: The Instant Flanger, Mk II.

In the Instant Flanger Mk II Plug-in,  we included the sought-after Feedback knob, as well as features unique to the digital version, such as Tempo Sync, Low Cut, Sidechain capability, and LFO retriggering.

In fact, we sent the new Instant Flanger and Phaser plugins out to those same studios with the original Instant hardware, and they couldn’t tell the difference. Here’s what some of them said.

Learn More

Instant Flanger Mk II Plug-in
Instant Phaser MK II Plug-in