PEARL's Products and Services   PEARL Tube Coolers have been in continuous production for 20 years, during which time over 300,000 pieces have found their way into audio systems the world over. Perhaps the longest running and most successful tube audio accessory of all time PEARL coolers have inspired a host of much more costly imitators, none of which combines the functions of cooling and microphonic reduction achieved by the long-established PEARL design. . . . .Based on research begun in the early 1950s by the US military and the aeronautical industry, PEARL coolers achieve the glass temperature reductions shown over 50 years ago to greatly increase the operating life of soft-glass enclosed electron tubes. Determined during the '50s research is the fact that the "soft glass" almost always used in receiving tube manufacture is susceptible to high temperature operation in that it becomes effectively "porous" at elevated temperatures, thereby allowing atmospheric contamination of the high vacuum within the glass. By several extensively researched and solidly confirmed mechanisms such contamination has been shown to have destructive effects on the electron emitting surfaces upon which tube functioning is completely dependent and extended tube life relies. . . . .Further, several tube manufacturers have clearly stated the benefits of envelope temperature reduction. In a Nov. 1959 manual Brimar Valves stated, "The use of close-fitting screening cans of high thermal conductivity in intimate thermal contact with a large area of the [soft glass] bulb, in conjunction with an adequate heatsink can materially reduce the operating bulb temperature and very considerably improve the life of the valve." Read more . . .   PEARL CryoValves are another of our industry innovations. . . . .While consulting in 1987 to Museatex, a Calgary-based company that has since grown into EMM Labs we were presented with an opportunity to chill down a quantity of tubes to -300ºF in Museatex' liquid nitrogen chilled "cold box" freezer. To say that we were taken by the changes wrought is to make rather an understatement . . . and after much research and development we have been treating tubes ever since. . . . .Over the years an entire industry has sprung up following our lead, with two of our previous customers having purchased cryogenic treatment equipment of their own. Noteworthy however is the fact that our cryogenic treatment is an immersion process we run for fully 100hrs. at a -325ºF soak temperature. This, as opposed to the 8hr. "soak" in what amount to the "cold boxes" chilled to typically only -300ºF by liquid nitrogen vapor alone employed by those following our footsteps. Because the extent of metallurgical change that occurs during cryo-temperature processing is a "time at temperature" product, longer treatment at lower temperatures will produce more of the changes so beneficial to audio performance. . . . .Subsequent to cryo treatment we do a 100hr. vacuum enhancement procedure followed by a lengthy triple-anneal process. Following these processes we do a 100hr. burn-in during which stochastic electrostatic forces are employed to further stress relieve the tubes' inevitably vibration sensitive and often highly resonant grid structure(s). This done we clean and polish away the hard, and very bad sounding oxide coating from the thru-glass pins not cleaned by the manufacturer, as most are not. Finally, we do a comprehensive series of parametric, gain (and gain match in dual triodes), noise and microphony measurements and provide all the data on the box in which the tube is shipped. . . . .While others claim to provide the industry's best services, we remain the process innovators and continue to provide a level of service that is simply unmatched, much less bettered. Read more . . .         PEARL Iso-sockets uniquely isolate 7- & 9-pin vacuum tubes from structure-borne vibration . . .

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