|. . . .PEARL TUBE COOLERS have been doubling the service life of hot-running
audio vacuum tubes for nearly 30 years, during which time over 300,000 pieces have been fitted into audio systems
the world over.
. . . .Perhaps the longest running, best
documented, best warranted and most successful tube audio accessory of all time PEARL TUBE COOLERS have inspired several much more costly imitators;
none of which combines the functions of cooling and microphonic reduction, nor anything like the cost/benefit ratio
achieved by the long-established PEARL
. . . .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.
. . . .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 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 198 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. It
can be downloaded here while a 3 page “Quickstart Introduction” is available
. . . .As of Jan. 1, 2017, PEARL TUBE COOLERS are underwritten
by a lifetime, transferable end-users' warranty that is also retroactive, 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
. . . .Dealer inquiries are welcome, we
have distribution openings in some countries and will advise.