Guitarsenal: The Eventide PS-101 Instant Phaser

Eventide PS-101 Instant Phaser

Manufactured by electronics company Eventide, the PS-101 Instant Phaser, was the effects unit used by Jimmy while recording the albums "Physical Graffiti" and "Presence".  For those who don't know, a phase effect is essentially an audio signal processing technique used to filter a signal by creating a series of peaks and troughs in the frequency spectrum. The position of the peaks and troughs is typically modulated so that they vary over time, creating a sweeping effect sound.

Of all the phase effects units manufactured, the most commonly used is the MXR 90 (which consequently is what is on Jimmy's modern day pedal board) which MXR began introduced in 1972.  However, in the mid 1970's when Jimmy was looking to add phase effects to his arsenal for the Led Zeppelin album "Physical Graffiti" he chose to overlook the Phase 90, and went for something a bit more versatile, The Eventide PS-101 Instant Phaser.

The Eventide PS-101 was manufactured from 1971 through 1977 and offered the user a tremendous level of versatility. The unit let you determine the mix of phased and direct signal, control the speed/rate of the LFO wave that controls the effect, set the input signal level which triggers phasing determine the phase decay time (0.01 to 10 secs.) could be controlled by LFO, knob, remote pedal or input envelope. It's very easy to see why Jimmy favored it.

The effects unit can be heard all over the tracks on "Physical Graffiti" and is featured quite notably on the guitar opus "Achilles Last Stand" from the band's album "Presence". Jimmy stopped using the PS-101 after 1977. Interestingly enough, the unit was also used to add phase effect to John Bonham's drum sound on the songs "Kashmir" and "Moby Dick" between 1975 and 1977.

"Achilles Last Stand" Live in Seattle 1977