For 40 years, Jensen has been synonymous with high quality/high performance transformers. From the beginning, Jensen has always been “open source” — its comprehensive product information, application notes and white papers have long been accessible to manufacturers and DIY’ers alike. And whether in 1974 or 2014, Jensen products continue to make a significant mark on the industry.
Time Travel
In order to understand founder Deane Jensen’s motivation, we set the DeLorean back to the mid-60’s and to see what challenges sent him on his quest. The Beatles’ Revolver had been on the charts for four months when Deane arrived in Hollywood in 1966; Sgt. Pepper’s was just six months away. The Beatles struggled with hearing themselves and being heard live over a cacophony of screaming voices. At that point, recording and live audio were about to take a major growth trajectory in parallel with (and eventually benefiting by) the space program.
Vacuum tube and discrete solid-state technology (AKA transistors) existed side-by-side in the 1960’s. Both topologies required input and output transformers to interface with each other. Having ushered in the first wave of miniaturization, discrete transistor opamps appeared in various forms, the most familiar being the API-2520. By the mid-70’s, IC opamps allowed live mixers and recording consoles to expand inputs, outputs and functionality in the same — if not smaller — frames.
Deane worked for console manufacturer Quad Eight (1968 – 1971). While consulting for Wally Heider in 1972, he was sent to API in New York to resolve technical issues before the console was shipped. Deane was part of Heider’s remote team for Bob Dylan’s live recording of Before the Flood and understood the critical relationship between solid-state amps and transformers, knew what shortcuts were being taken and, rather than accept the status quo, set out to resolve those issues. Through science, he knew what paths could achieve the goal.
Bill Whitlock Comes Aboard
Planning his exit strategy from Quad Eight Electronics, Deane interviewed Bill Whitlock as his replacement. In Whitlock, he found a kindred spirit — their friendship and professional partnership had them working on projects together for two decades until Whitlock officially became president of the company in 1989.
While in college, Whitlock met Stephen Desper who in 1965, worked with The Beach Boys, who used Quad Eight Consoles. Whitlock designed a varispeed circuit for their 3M tape machine and at QE, he designed Compumix — the first add-on console automation. From 1974 to 1981, he applied that automation knowledge to Laserium (the laser light show) and patented a multi-channel PCM audio recording system that included control tracks.
In 1994 and 1995, two of Whitlock’s AES Journal papers advanced the understanding of ground distribution, power and ground-related noise and audio signal distribution. “Balanced Lines in Audio: Fact, Fiction, and Transformers” along with his work on the AES standards committee, resulted in the AES48 interconnection standard, while, his suggested changes to the IEC’s CMRR measurement standards were adopted in 2000. Since 1994, Whitlock has done master classes at industry trade shows around the world and written for many trade publications.
The Industry Evolves
While Deane was Founding Jensen Transformers in 1974, 16- and 24-track recording became more common. More tape tracks meant more individual mics and those mics were placed closer to instruments and increasingly louder guitar/bass amps. Proximity effect increases a directional microphone’s LF output so that, when combined with high SPL’s, a transformer’s core material can easily saturate. “That’s never been an issue with Jensen Transformers,” according to Whitlock, “because we designed so conservatively and based the level-handling rating at 20 Hz, which is more critical than using the mid-frequency spec.”
In live venues, louder stage amps, bigger P.A.’s and more complex lighting systems put increasing demands on power and ground distribution. Lighting was a consistent noise source back then when instrument amps had two-pronged power plugs and Fender amps had a “death switch” that tied either side of the AC line to chassis (as needed). And yes, it was someone’s job to hold a guitar, walk up to a mic and make sure there was no “lip tingle.” When remote audio trucks interconnected with the house system, there was inevitable problem of keeping it all noise-free. Transformer isolation was a necessity.
Deane realized that transformers played a huge role in every aspect of the signal chain — from the source microphone to the preamp, mic splitters for mains, monitor mix and remote recording — essentially on the input and output of every device. According to Whitlock, “Deane’s work on the Heider/API project let him identify which transformers were responsible for the reported ‘bad sound’ and the comparison measurements between those and other ‘more likable’ transformers was essentially the ‘aha’ moment.”
Like many entrepreneurs, Jensen started in his apartment, working with Ed Reichenbach, whose company had been supplying custom transformers to Altec, Electrodyne, Langevin and Quad-Eight. “In some sense,” Whitlock clarified, “Deane didn’t discover anything really new or ‘patentable,’ he just wasn’t willing to compromise perfect square-wave/time-domain response for the sake of price.” A square wave can be very challenging for some circuits to reproduce.
Electrically Speaking
Transformers are three-dimensional entities. Beyond the obvious two-dimensional specs like frequency response, there are hysteresis challenges (not unlike recording tape) that produce different distortion components at low and high levels. In any circuit, there are trade-offs between the primary task and the side effects. Transformer windings have resistance, inductance and capacitance — together, these components make a passive equalizer. The resulting time-related idiosyncrasies (like phase shift) are part of a series of very complex equations.
Jensen felt he could apply computer science to optimizing LF clarity and definition, controlling harshness in the presence region, extend HF response and position the type and amount of phase shift where it was least objectionable. In more familiar terms, he optimized his transformers to have the frequency response of a Bessel low-pass filter.
Deane created Comtranâ, a CAD program that helped optimize his transformer, filter and amplifier designs. Comtran was the first third-party software developer for HP and as a result, countless engineers benefited from his work. Jensen created stringent tests for core materials before they became part of a finished transformer. By 1974, Jensen’s JE series quickly had users evangelizing their merits. In addition, his DI and mic-splitting transformers included double Faraday shields (unique to Jensen), making them much more effective in noise-challenged environments.
In the mid-to-late 70’s, it was not uncommon to remove transformers from the signal chain. “Transformer-less” became a multi-pronged solution — equal parts technical, marketing, and economic, in terms of cost, weight and real estate. The 4-resistor balanced input amplifiers of the time did not provide nearly the common mode rejection ratio (CMRR) of a transformer. That said, Whitlock created a true electronic equivalent — the InGeniusâ balanced line technology he licensed to That Corporation in 1994. That’s 1200 series of balanced line receivers are incorporated into many modern products today.
The 990 Opamp and Expansion
In addition to transformer design improvements, Deane published the details of his new 990 discrete opamp design in a 1979 AES Journal. Today, companies often withhold schematics and other documentation, but that article included the 990 schematic (patent #4,287,479). Deane’s goal was to improve the state of the art; he wanted everyone to benefit. The 990 surpassed other amplifiers of the time in terms of noise, distortion, slew rate, stability and output drive (power).
As demand for Jensen Transformers increased, the company moved to a larger building in North Hollywood (1980). Dave Hill became the facility manager and is currently VP of Operations.
Tragedy and Rebirth
A 1983 bicycling accident left Deane in a wheelchair for several years. During his recovery, Deane moved into the facility and hired a personal assistant. After he recovered, Whitlock persuaded “the man who never takes vacations” to go to Hawaii with in June 1989. But on his return, the strain of driving the small company through his recovery overwhelmed him. Deane took his life in October 1989, leaving the company to his trusted friend, Bill Whitlock. Deane Jensen was posthumously inducted into the TEC Hall of Fame in 1990, along with Quincy Jones and George Massenburg.
Radial Engineering’s Peter Janis was introduced to Jensen Transformers in 1981 while working at a music store in Edmonton. One day, the electronic repair tech — who also happened to also be a first-call session bass player — opened a small handmade direct box and pointed to one of the first Jensen transformers to come to Canada. Ten years later, Janis launched CableTek (later Radial Engineering), with Jensen transformers among its first imported product lines. The Radial JDI (AKA Jensen DI) was launched in 1996.
Radial Engineering purchased Jensen Transformers in July 2014. “As Jensen’s number one customer,” Janis explains, “we felt that investing in the necessary equipment to increase production capacity would satisfy the needs of both Radial and Jensen customers.” The specialty equipment consisted of two $50,000 Swiss-made Meteor numerically controlled coil winders. This pair increased Jensen’s total to seven, one of which is devoted exclusively to R&D.
“In all of our tests — electrical, noise and listening — Jensen models always come out on top.” Janis added that “we are now working at improving inventory management systems, accounting, sales & marketing — all the stuff that a typical engineering firm tends to put aside.”
Today, Jensen Transformers continues under the guidance of original team members Bill Whitlock and Dave Hill. For more info, visit jensen-transformers.com.
Eddie Ciletti designs and services audio gear through his company, Manhattan Sound Technicians, Inc. Catch him at tangible-technology.com.
