Application Note (112020)- Type 300B Electron Tube
This note furthers our commitment to quality by communicating supplemental details and helpful insights about our product.
A NOTE ON ANODE COMPOSITION
The change in appearance of the anode (plate) component of the Western Electric 300B (pictured above) is the result of years of research and effort to improve the anode coating process.
By coating the plate with graphene, rather than carbon, our engineers have improved the 300B’s capacity for thermal emissivity and electrical conductivity between the plate and filament. Graphene’s single atomic layer adheres to the proprietary, “five-nines” pure nickel alloy of the plate, sustaining a higher vacuum that significantly reduces gas evolution detrimental to tube life over time. In addition to extending tube life, this improvement yields higher average plate current and dramatically reduces the effects of secondary emission.
The Western Electric anode coating process is patent pending.
A NOTE ON FILAMENT BURN-IN
The filament of a Western Electric 300B is aged or “burned-in” for nine hours following strict procedures established by Bell Laboratories engineers. While this initial duration is sufficient to meet quality control standards, a 300B sometimes requires additional time, in some cases up to 500 hours, to reach its full potential during music playback. Many end users report a significant improvement in sound quality after just a few hours of regular use. Put simply, burn-in is a natural process that continues after 300B electron tubes leave our manufacturing facility for end use.
If after 48 hours of regular use you are still not satisfied with the performance of your electron tubes, revisit the operating instructions included with your 300B purchase or contact Western Electric support by emailing support@westernelectric.com or by calling +1 (404) 352-2000 during regular business hours.
A NOTE ON MICROPHONICS
The Western Electric 300B is a filamentary device operating as a directly heated cathode. Because of their mechanical structure, electron tubes with directly heated cathodes (commonly abbreviated DHT) are inherently more microphonic than electron tubes with indirectly heated cathodes. With this in mind, the 300B, when used in an amplifier’s gain stage (pre-amplifiers or headphone amplifiers for example), is more susceptible to microphonic noise and extra care must be taken. The 300B is designed for and traditionally used in an amplifier’s power stage.
We recommend 300B users take extra precautions, such as implementing elastomer-isolated tube sockets, to help minimize or altogether eliminate unwelcome microphonics during operation if used as a gain stage.
Users may also experience noticeable yet gentle “tink” noises during amplifier startup or warmup. These sporadic noises are caused by glass expansion. As the glass bulb of a 300B adjusts from room temperature to a higher temperatures during normal filament operation, it expands. Glass expansion does not affect normal operation and is not detrimental to tube life.