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PEARL, INC. - Electron Tube Coolers for Increased Service Life |
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| . . . .PEARL TUBE COOLERS
have been doubling the service life of hot-running audio vacuum tubes for 35 years, during which time over 100,000
pieces have been fitted into audio systems the world over. . . . .Almost certainly the longest running, best documented, best warranted and most successful tube audio accessory of all time, PEARL TUBE COOLERS have inspired several over-priced, under-performing imitators none of which combines the functions of cooling and modest microphonic reduction, nor anything like the cost/benefit ratio achieved by the long-established PEARL design. . . . .Continuously refined, our heatsink design has evolved from an oxide blackened, louvered fin device with black EDPM O-rings — later found to have inadequate long-term thermal withstand — to the present day solid copper device with 3D-contoured, contiguous fins coated with 2 mils of high metal content, high temperature powder coat and held in place by high thermal withstand, red-orange, silicone O-rings. . . . With heat from the within tube’s envelope and pressure from the external O-rings the powder coat slightly softens to then flow in a conformal manner with an intimate thermal interface and unmatched microphonic control resulting. . . . .Based on research begun in the early 1950s by the US military and the aeronautics industry, PEARL coolers achieve the sorts of glass temperature reductions shown over 60 years ago to greatly increase the operating life of soft-glass enclosed electron tubes. . . . .Conclusively determined during the 1950s research is the fact that the “soft glass” typically 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 service life relies. . . . .All major vacuum tube manufacturers of the day clearly illuminated the benefits of envelope temperature reduction. |
. . . In an article that appeared in the April 1953 issue
of Electronics magazine that was subsequently reproduced for distribution by RCA and republished by Radiotronics
in Australia we read: . . . “Tube life, in general, can be extended by maintaining low temperatures for the glass envelope. This is especially important in high-power output tubes because of their higher plate and cathode dissipations.” . . . From the data sheet for the fabulous Bendix Red Bank 6900: . . . “Special attention should be given to the temperatures at which the tubes are to be operated. Reliability will be seriously impaired if maximum bulb temperature is exceeded.” . . . In a Nov. 1959 data manual Brimar Valves, UK 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.” which is an exact description of the PEARL electron tube cooler's form, function and effect. . . . The 200 pg. PEARL Audio Note, “PEARL TUBE COOLERS and Equipment Reliability” provides both a present-day overview and several magazine reviews as well as an extensive overview of the period literature and patents. Also available is a “Quickstart Introduction”. . . . As of Jan. 1, 2017, PEARL TUBE COOLERS are underwritten by a lifetime, transferable, retroactive warranty, meaning that every PEARL cooler in the hands of an end-user is now warranted against defects in materials and/or workmanship. . . . If your coolers have black O-rings, please contact us for no-charge, replacement, high temperature, silicone O-rings. |
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Tube Coolers for Small Signal Tubes. |
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Tube Coolers for Power Tubes. |
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