Jimi Hendrix often dreamt of sounds he wanted to bring out through his music. He also associated colors with sounds, visualizing the color purple as jealousy or anger, the color green as envy, and the full spectrum of a rainbow as a special girl in his life. The musical colors painted a 3-D effect of emotions that he wanted to portray throughout his music, much as an artist would use a paintbrush and paint to bring out images they envisioned. Jimi always searched for the next new sound effect that could enhance his recordings and guitar tone. He would discuss with his engineer, Eddie Kramer, recording techniques that could somehow re-create the tones he heard in his head.
On October 29, 1967, during a recording session for Axis: Bold As Love at Olympic Studios, Jimi described to Kramer a tone he heard in a dream that sounded "underwater." Earlier, Kramer was working with George Martin on a Beatles recording using artificial doubling tracking (ADT). This technique was used on the Beatles tracks "Baby Youre a Rich Man" and "All You Need Is Love." The technique created a phasing effect when two identical recording tracks were played simultaneously, but placed slightly out of sync. Jimi realized this technique was on the right track, but it didnt quite match the sound in his dream. Hendrix and Kramer enlisted George Chkiantz, a fellow engineer at Olympic Studios, to fine-tune the process to create the thick phasing tone Jimi heard in his dream. Chkiantz finally came up with the effect they were after and it was used on tracks of the album.
Phasing was only the beginning of various effects used in the studio. Also during this recording session at Olympic Studios, Hendrix and Kramer experimented with running the guitar and vocals through a Leslie Speaker on the Hendrix classic "Little Wing." The Leslie speaker was originally used for the electronic Hammond organ. The design of the speaker was based on the physics of the "Doppler Effect." As a kid, did you ever take a rope and swing it around your head in order to achieve a surround audio effect? This phenomenon is termed by science the "Doppler Effect"-- the physics of sound, light or other wave sources moving toward or away from the observer. Most of what we observe in nature is based on the physics of waves due to variable frequency and intensity. Our ears perceive such audio wave sources as sound or music. The first instrument designed to utilize this effect was the electronic Hammond organ. Most organists played solo and needed to fill as much audio space as possible in order to achieve the intensity of a full orchestra. Thus the Leslie Speaker was invented by Don Leslie to enhance the organs tone with this rotary speaker design. The most common Leslie Speaker was the model 122. The cabinet was made of walnut, encasing a two-speaker system on a low frequency 15-inch speaker with a ported rotating drum and a double high frequency horn, both driven by a motor and belt system rotating the sound horizontally 360 degrees. The amp section was rated at 40 watts and was driven by 12AU7 and 6550 tubes, capable of handling up to 60 watts. The signal ran into a crossover set at 800 HZ and split the signal into the high and low speaker system. The pre-amp had two speeds, a slow setting that created a "choral" effect and a fast setting that created a "tremolo" effect. When pushed to upper volumes the system would produce a great distorted sound. This system soon gained popularity and was eventually adopted by guitarists. The down side of the Leslie speaker system was the size and weight of the cabinet(s). Most guitarists only used this effect for a few songs, as it was impractical to carry on the road.
Roger Mayer was a local electronics wizard who would often show up at Jimis recording sessions with various guitar effect designs for Jimi to try out. Recognizing the need for a pedal that could re-create the effect of a Leslie Speaker, Mayer soon had a prototype of a pedal based on a four-stage sweep filter that eventually evolved into the Uni-Vibe. The Uni-Vibe was portable and produced a thick sound reminiscent of the Leslie Speaker. Jimi knew Mayer was on to to something and soon adopted the guitar effect as a main component of his unique guitar tone.
You can hear the Uni-Vibe throughout Jimis later album. Songs that stand out are "Hey Baby (The Land of the New Rising Sun)," "Dolly Dagger," and "Pali Gap." This effect especially stands out on the song "Machine Gun" on Band Of Gypsys. The Cry of Love features some excellent examples of Jimis use of the Uni-Vibe, on cuts such as: "Angel," "Drifting," "Night Bird Flying," and "Astro Man." You can hear the "tremolo" effect of the Uni-Vibe on a cut from Rainbow Bridge called Earth Blues. August 1969 Jimi used the Uni-Vibe for the first time in his live stage setup at Woodstock. You can hear this throbbing effect in his "Star Spangled Banner" adaptation, and on other songs played that day. After Woodstock, the Uni-Vibe became a constant companion in Jimis stage setup. His gear was set up in this order: a Fender Stratocaster, Vox Wah Wah, Octavia (occasionally), Arbiter Fuzz Face, Uni-Vibe, into his Marshall stacks.
The Uni-Vibe was designed in a 10 x 7 inch rectangular metal case that sat on the floor in front of the guitarist so he could control it with his foot. The control was a 2-way switch that allowed the guitarist to change from "chorus" to "vibrato". The chorus gave the effect of the Leslie speaker rotating at a slow speed, which was a common setting that Jimi used. The vibrato setting created a faster, throbbing tone that was often used in "Surf" songs. Fender specially built this effect in many of their amplifiers because of the popularity of this sound. You can find this effect in several models, such as the Fender Tremlolux, Vibrolux, and Vibro-Champ. There is an intensity knob that controls the mixing of the rotating effect into the original signal. The signal to noise ratio was quite low and low on hum. A volume control knob to adjust the units output volume. An external foot pedal, looking much like the Wah Wah pedal, can be plugged in to the unit to control the speed with your foot by means of a special cable and multi-pin jack. The Wah pedal also controls the effect on and off. This gives the guitarist more freedom to control the chorus or vibrato effect while playing the guitar at the same time. Other controls include an on/ off switch and two color red and green led lights to let the guitarist know what mode the unit is set in.
The Uni-Vibe was first manufactured in 1969 by Uni-Vox. The unit came in two versions, an American version with a 110 volt transformer, and a British model that had a 240-volt transformer. A photo light cell controller was at the heart of the design of the effect unit. This device consisted of four photo resistors and an incandescent lamp. No two units sounded exactly the same due to the setting of this mechanism. The units could be fine-tuned by adjusting these parts and could even be set to sound quite musical. There was a problem when the unit was played under cold conditions, however the manufacturer suggested that a five-minute warm-up period would help the performance of the unit under cold conditions. The rest of the components consisted of various resisters (68k, 100k, 200k, etc.), capacitors (100uF/25V, 220uF/25V, 1000uF/25V, etc.), LFO (Low frequency Oscillator), and other parts. The Uni-Vibe was discontinued after 1970 and was briefly manufactured by a Japanese company called Shin-ei in the mid-70's with a 240-volt transformer designed for European markets. Roger Mayer later produced a rack mount version with an upgrade to the oscillator and a true bypass in the unit, which avoids the direct signal being affected when the unit is off.
A 1969 Uni-Vibe can currently go for up to $900 in the vintage guitar market. Thats amazing considering the unit originally retailed for $110 in 1969. Currently Jim Dunlop is producing various products that produce the Uni-Vibe effect. The Dunlop Uni-Vibe and Roto-Vibe models are both excellent products and quite reliable. Renewed interest in Jimi and his music has spurred sales of these products.
Jimi was at the cutting edge of creating guitar tones that never before existed. The influence of his pioneering spirit is still with us today and alive in many musicians who continued to carry his standard of musical excellence. Stevie Ray Vaughan and Robin Trower are among the guitarists who attributed their sound to Jimi Hendrix. Jimi will always be alive to the countless people who still hold his music dear.