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The History of Spectra 1964

Updated: Oct 8, 2019

The history of the pro audio equipment recording company, Spectra Sonics, the legacy company that eventually became Spectra 1964, began humbly in a home basement. At the time, our founder, William G. Dilley, was a constant contributor for Audio Magazine, the United States' longest running audio magazine, and also, the Journal of the Audio Engineering Society, the only peer-reviewed scientific journal devoted exclusively to audio technology. Utilizing his expertise, Dilley started his electronic legacy with "Custom Engineering by Dilley," a company dedicated to advanced tube-design preamplifiers, mixers, and power amplifiers. We still have many of Dilley's original tube-based designs.

In 1964, Spectra Sonics was formed based entirely on solid state, discrete designs. As can be easily tracked via journals published between 1964 and 1969, the transition from tube technology to the introduction of the famous 101 solid state preamplifier module took less than 18 months. Incredible! Essentially, all of the technology we currently use today at Spectra 1964, was developed between 1965 - 1969!

Originally, Spectra Sonics provided individual amplifier modules, card frames, power supplies, and equalizers for small manufacturers and in house engineers who wanted to build custom consoles. Auditronics from Memphis built the Stax and Ardent consoles. TTG and A&M Records and others assembled custom consoles that exist today. Several hundred consoles were built in this manner. Folks like Flickinger and Cadco used the Spectra Sonics components to build famous consoles like what were found at Muscle Shoals and Tom Dowd’s group with Atlantic Records, Studio C.

Spectra Sonics 101/500 unit @ STAX Recording, 1967

In 1964, Spectra Sonics introduced the 101 preamp. The 101 offered performance not previously seen by the recording industry, including: -127.5 unweighted noise, distortion below .01%, 20-20kHz, and the elimination of impedance matching with outboard circuits. Adding to the technological advance, Spectra Sonics introduced an audio amplifier that did not overload with audio program transient peaks, thus eliminating of the need for peak light indicators, and the use of Vu meter monitoring.

In 1968, due to poor performance in terms of physical console fabrication and improper circuit termination, Spectra Sonics began to produce consoles. At the time, they were the only firm in the industry that could deliver a console from stock. Approximately 50 consoles were built during this period at an average price of $35,000.00. The more expensive consoles were purchased by Record Plant NY and LA, as well as Michael Jackson and The Carpenters. It can be safely stated that during this period, a majority of Gold and Platinum Recordings produced during this time were crafted on Spectra Sonics gear.

Around this time, Spectra Sonics also developed the first compressor limiter that could provide independent, or combined, peak-limiting functions. The “Complimiter” went on to become an industry standard. With a limiter attack time of less than 90 nanoseconds, the 610 not only became the standard for use with tape machines and record lathes, but after 40 years it is still the world's fastest audio peak limiter / compressor.

The 610 Complimiter was the first device of this type to eliminate compression pumping, and the need for de-essing, and maintained full bandwidth at ratios of up to 100:1. In addition, the 610 is one of the few, if not the only, device of this type, that rivals the best microphone pre’s in terms of noise and distortion. Combined with an input threshold of -40dBu, the 610 offers the user the best of all worlds, peak free transients, adjustable compression and low noise and distortion and considerable amplifier gain, (56-65dB depending on the model).

An important fact to note is that there have been no revisions or changes on the core circuit design since the introduction of each respective product. That goes for the 101 and 110A modules as well as the 610 Complimiter.



Introduction of the first modular discrete preamplifier module that required no impedence matching, had dc stability, so thermal issues were eliminated, had peak overload of up to 1000% in less than one microsecond. This module had less than 1 degree of phase shift to 100kHz, with unequaled noise and distortion.


Introduction of the first independent compressor/limiter that had noise and distortion that rivaled any conventional mic pre. Compression was continuously variable from 1:1 to 100:1. Release time was up to 10 seconds.


Introduction of the first modular biamp/triamp power-amplifier system available to the industry. First console manufacturer to guarantee input to output, noise, distortion, and less than 1 degree of phase shift to 100kHz.

In later years with the introduction of the famous 701 power amplifier, the modular multiway power amplifier system would be specified by many of the world’s leading acoustical design houses. From the Radio City Music Hall to the Keelung National Theatre in Taiwan, to Concord Pavilion, as well as the Hollywood Bowl and Whiskey Agogo. Spectra Sonics 701 power amplifiers were employed in hundreds of installations throughout the world. Availability of the Spectra Sonics 701 and 712B power amplifier, was suspended in 2006. However, support for the 701 series product line continues.


Consumers Union adopts the Spectra Sonics console and power amplifier technology as the reference system used in Consumer Reports test reviews of audio products.


Spectra Sonics purchased Spectra Sound Incorporated, from the two current owners of Spectra Sonics, LLC. The addition of Spectra Sound Model 1000B and Model 1500 outboard equalizers, and the introduction of the now, well known, Model 1100 outboard mixer, allowed Spectra Sonics to move, with great success, into the fixed-sound reinforcement business. Support of Spectra Sonics and Spectra Sound products has been maintained consistently, without interruption, and continues today.


Warner Communications began employing the Model 610 Complimiter as their head-end audio limiter, and volume compressor. The installation base for this package ran into the hundreds, and continues to be supported.


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