Mr. Dilley, an engineer and a pilot, received his education from the University of Colorado before and after flying as an officer in the United States Army Air Corps during World War II.

In 1964, he founded Spectra Sonics in Ogden, Utah. Specializing in professional audio equipment for recording studios, broadcast (radio and television) performing arts center, motion picture studios, and other such related endeavors, his distribution network became world-wide. In addition to audio product design and manufacture, Mr. Dilley designed, for license, other non-allied electronic equipment and acted as a consultant to major United States business firms. In 1970, he was awarded a fellowship by the Audio Engineering Society, Inc. for advancing the “state of the art” in audio control console design, and in 1977, he was designated a Senior Broadcast engineer by the Society of Broadcast Engineers. Also, in 1977, he was the recipient of the University of Colorado Distinguished Engineering Alumnus Award, the highest honor the University can bestow upon an alumnus. Remaining active as a consultant and lecturer in the field of electronics, Mr. Dilley published over 300 engineering papers and technical articles, and was the holder of 14 United States and foreign patents.

Throughout his engineering career, Mr. Dilley remained active in the field of aviation. He flew in excess of 150 different types and models of aircraft. Mr. Dilley flew combat in fighter air craft, shot down enemy ground fire; bailed out, bellied-in, and crashed. He piloted 4-engine passenger transport aircraft on scheduled flights throughout the Pacific Ocean and has conducted operational tests of jet fighter aircraft. He commanded fighter squadrons, and directed fighter operations as a Group Operations, Wing Operations, combined Combat Operations, and numbered Air Force Fighter Operations. Mr. Dilley was an organizing member of the “MINUTEMEN”, an air acrobatic team, flying P-51 type aircraft. He personally planned and participated in the first, and only, F-86 Mass Jet Flight (83 aircraft) to fly the Atlantic Ocean. He participated in establishing instrument approach procedures for jet aircraft,  and established many published approaches, both in the U.S. and Europe. While in Europe, he commanded the number one, or top-rated, tactical unit in all of the United States Air Forces Europe, and personally wrote, coordinated, and published the joint air/ground operations manual for the U.S. 12th Air Force and the U.S. Sixth Army. He activated air bases both in the United States and Europe to include all operations, communications, and navigational requirements. He formally investigated numerous aircraft accidents for the U.S. Air Force Directorate of flight Safety Research. He was one of a very few Air Force officers selected to advance the technological capability of the Air Force, by pursuing advanced education of his choice at any institution of his choice. He personally landed aircraft in over 5,000 cities of 87 different countries and possessions of the world, and was the holder of United States and World speed records.

Mr. Dilley was Chief of Engineering for operational aircraft and related system, Chief of Engineering for air munition, and chief of Electronic Engineering for the ballistic missile systems: Thor, Atlas D, Atlas E, Atlas F, Titan I, Titan II, and Minuteman I. He personally conceived and was responsible for the design, acquisition, and operation of the first fully instrumented engineering test facility for a missile system: The Minuteman. 

In his engineering capacity, he was singularly responsible for reducing, significantly, the required “count-down” time for missile prior to launch. 

Mr. Dilley prepared an uncountable number of technical and operational studies, and managed a myriad of multi-million dollar programs, and the Science and Technology Division of the Library Congress has identified him as one of the prominent engineers in the United States. In 1994, the College of Engineering of the University of Colorado selected him to receive their Centennial Medal, in recognition of significant career achievement having lasting influence on society and the engineering profession. 


The history of Spectra started with a prior company named “Custom Engineering by Dilley”. William G. Dilley, the founder of both firms started with advanced tube design preamplifiers, mixers, and power amplifiers based entirely on technology of the day. Mr. Dilley was a constant contributor for Audio Magazine and the AES Journal. (We currently have many of Mr. Dilley’s original tube based designs that were covered under the articles).

In 1964, Spectra was formed based entirely on solid state, discrete designs. As can be easily tracked via published articles of the day, the transition from tube technology to the introduction of the famous 101 solid state preamplifier module was less than 18 months. From 1965 to 1969, essentially all of the technology we currently use today at Spectra Sonics, was developed.

1964 The introduction of the 101 design. The 101 offered performance not seen by the recording industry, -127.5 unweighted noise, distortion below .01%, 20-20kHz, and the elimination of impedance matching with outboard circuits. Added to the technological advance, was the introduction of an audio amplifier that did not overload with audio program transient peaks thus eliminating of the need for peaks light indicators, and the use of Vu meter monitoring only.

Originally, Spectra provided individual amplifier modules, card frames, power supplies, and EQ’s 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 used the Spectra components to build famous consoles like were found at Muscle Shoals and Tom Dowd’s group with Atlantic Records, Studio C.

In 1968, due 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. I can be safely stated that during this period, a majority of Gold and Platinum Recordings were done on Spectra.

During this period, Spectra developed the first compressor limiter that could provide independent, or combined peak limiting functions. The “Complimiter” went on to become a standard by which other like devices were compared. 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 compressor.

The 610 Complimiter was the first device of this type to eliminate compression pumping, 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 impedance matching, had dc stability, so thermal issues were eliminated, peak overload of up to 1000% in less than one microsecond, less than 1 degree of phase shift to 100kHz, and unequaled noise and distortion


Introduction of the first independent compressor/limiter that had noise and distortion that rivaled any conventional mic pre. Compression continuously variable from 1:1 to 100:1. Release time 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 the 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, Spectra 701 power amplifiers were employed in hundreds of installations throughout the world. Availability of the Spectra 701 and 712B power amplifier, was suspended in 2006. However, support for the 701 series product line continues.


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


Spectra 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 begins employment of Model 610 Complimiter as head-end audio limiter, and volume compressor. The installation base for this package ran into the hundreds, and continues to be supported.


From the start, William G. Dilley was famous for his technical lectures. A large chalk board would usually accompany him as he detailed the difference between Spectra and other manufacturers. As part of the lecture, Mr. Dilley would describe the concept behind the company logo. Essentially, it was the goal of all Spectra amplifier designs, "to accurately reproduce the input waveform at the output of the device, with the required gain for the application". The dual input/output waveforms on the logo represent that mandate. All Spectra products since 1965, have referenced this logo as part of this unique performance guarantee.