For purchase is (2) Sovtek EL84M / 6BQ5 Matched and Cryo Treated Vacuum Tubes.
Sovtek EL84M's extended voltage tolerance, improved plate dissipation, and rugged construction make it equivalent to the RCA 7189. Chosen by Matchless for their designs, the EL84M also features higher transconductance, more power, and longer life than the less expensive EL84, making it perfect for hi-end audio applications. However, many musician's prefer the regular EL84's warm distortion to the EL84M's tighter, cleaner tone. For all HiFi users, the EL84M is definitely the tube of choice.
Cryoset Deep Cryogenic Treatment:
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 dynamic range, micro detail with an increase in speed.
Bass response has been clearer with a reduction in micro phonics.
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 (Fahrenheit) 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) has been shown to be modified after cryogenic treatment, creating a more uniform or homogenous microstructure. The thermal dissipation properties of the metals are 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 relieves stresses and normalizes (or stabilizes) welded and soldered areas. This mechanism is founded in the observation first made by Bose 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 Fahrenheit) 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 Fahrenheit for an extended dwell time enables the material to become more relaxed and stress relieved. The transformations as a result of cryogenic treatment is permanent, and does not change with time.