from cryoset.com
What is Cryogenics?
The proprietary Cryoset treatment process utilizes a computer controlled, cryogenic chamber to very gradually reduce the temperature of the tubes to 300 degrees below zero (Farenheit) and holding them there for a minimum of 24 hours. After the extended dwell at this cryogenic temperature, the vacuum tubes are then very slowly brought up to ambient temperature over the next 24 hours and stabilized. The process is a "dry" one that utilizes Liquid Nitrogen as a cryogen that is flashed into the chamber. The tubes are never exposed to the actual liquid. All these processes are microprocessor controlled under strict and verifiable conditions.
Scientists have known for years that material transformations occur when they are exposed to cryogenic temperatures. Many of the early discoveries were more fully explored by NASA engineers who were trying to understand what would happen to metals when subjected to the extreme temperatures of space. Today, a wide range of commercial items - from softball bats to race engines - are cryogenically treated to improve their performance by enhancing the material properties with "cold treating" or cryogenic processing.
This technology brings practical application to audio and other electrical components as well. Cryogenic treatment modifies the microstructure of the metals used in critical electronic components by reducing or eliminating voids and imperfections in the material. Crystal structures (or grains) have been shown to be modified after cryogenic treatment, creating a more uniform or homogenous microstructure. The thermal dissipation properties of the metals is improved, reducing hot spots and further contributing to extended life and improved performance. In addition, the physical contraction of the metals while under the deep freeze imparts a mechanical compression on the metals that contributes to improved signal transmission quality and speed.
The materials used in electronics are highly fabricated and the manufacturing processes used impart or induce stresses in them. In addition, welding and soldering adds additional stress from concentrated areas of heating. Most everyone recognizes that welded components often fail AT the weld -- a "weak" spot. The weakness comes from residual stresses inherent in all materials, further exacerbated by manufacturing techniques or processes.
Cryogenic treatment releives stresses and normalizes (or stabilizes) welded and soldered areas. This mechanism is founded in the observation first made by Bose (of Germany) and later by Einstein, that matter is at it most relaxed state when it has the least amount of kinetic energy (or molecular activity). Absolute zero (-459 Farenheit) is that point where no more energy can be extracted, or when a material is at its most "relaxed" state. While our Cryoset (R) thermal treatment does not get to absolute zero, you can understand how going to minus 300 degrees Fareneheit for an extend dwell time enables the material to become more relaxed and stress relieved.
The transformations that occur as result of cryogenic treatment are a permanent, one time modification to them.
The process makes a permanent change and the benefits do not deteriorate over time or upon return to operating temperature, it changes the whole way the vacuum tube performs. The major benefit has been a dramatic improvement in dymanic range. Bass response has been clearer with reduction in microphonics. The most starling fact has been how the tubes operates under saturated and overdriven conditions. This has made some of the more basic guitar amps sound fuller and warmer.
very expensive .... 
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