In 1971, studio effects racks were filled with pre-amps, EQs, limiters, compressors and very little else. Before 1970, nearly all studio ‘tricks’ were achieved electro-mechanically using tape machines for delay, flanging and phasing effects. The Eventide Instant Phaser was one of the first dedicated electronic effects unit and producers/engineers put it to use in subtle ways to create stereo images from a single source and to create swept comb filter effects similar to, yet distinct from, tape flanging. The Eventide Instant Phaser employed a series of eight, FET-based, carefully tuned analog all-pass filters which delivered lush phasing while preserving the original tone.
Before boxes existed, tape machines were the only way to achieve this effect and the terms phasing and flanging were used interchangeably. In 1971, the circuitry didn’t exist to delay audio electronically (pre digital, pre bucket brigade) so no one could build an electronic box that did what tape did (delay audio). Phase shift analog filters were a ‘trick’ to create a similar but definitely distinct effect so we called the box a phaser, not a flanger. When bucket brigade chips became available a couple of years later Eventide built the Instant Flanger which delayed audio – same effect as tape flanging.
- Function (Far Right Knob) – Selects one of the four control types that will modulate the phasing filters to create phase shifted effects. Only one mode and it’s corresponding set of controls can be used at a time.
- Depth – Controls the mix of direct and phase shifted signal. When fully clockwise, both signals are of equal amplitude; when fully counter-clockwise, only they phase shifted signal is present.
- Oscillator – Controls the rate at which the low frequency oscillator sweeps back and forth through the range of the phasing filters from .1-10 Hz. Slow speeds create a fading effect; high speeds produce vibrato like effects.
- Manual – Allows for full range control of the phasing filters based on the knob’s position.
- Envelope Follower – The Envelope Follower tracks the input signal’s amplitude to control the sweep of the phasing filters. In this mode, imagine that the input signal is tied to the Manual Control Knob. The louder the signal, the farther the knob turns clockwise.
- Threshold – Determines at which input level the Envelope Follower begins tracking the input signal to control the phasing filters. Clockwise on this control lowers the threshold making quieter signals have a greater effect.
- Release – Determines the rate at which the Envelope Follower returns to a lower state after the loudest signal has past. Clockwise on this control increases the release time and makes the Envelope Follower track more slowly.