Moderate power, filamentary triodes for Class-A service.
Audio-frequency amplifier in positions where power outputs of approximately ten watts or less are required at relatively low plate voltages.
Dimensions, outline diagrams of the tubes and bases, and the arrangement of electrode connections to the base terminals are shown in Figures 1 and 2.
Base and Mounting
These vacuum tubes employ medium, four-pin thrust type bases suitable for use in Western Electric 143B or similar sockets. The 300B tube has the bayonet pin so located that it may also be mounted in a Western Electric 100M, 115B, or similar socket.
The tubes may be mounted in either a vertical or horizontal position. If mounted In a horizontal position, the plane of the filament, which is indicated In Figure 2, should be vertical.
Average Direct Interelectrode Capacitances
Grid to plate 15 µµf.
Grid to filament 9 µµf.
Plate to filament 4.3 µµf.
Filament voltage 5.0 volts, a.c. or d.c.
Nominal filament current 1.2 amperes
The filaments of these tubes are designed to operate on a voltage basis and should be operated at as near the rated voltage as possible. When alternating current is used for heating the filament, the grid and plate returns should be connected to a center tap on the secondary of the filament transformer.
MANUFACTURED IN THE U.S.A.
Electron tubes carry a Limited Warranty of ninety (90) days to the end user. The Limited Warranty period may be extended to five (5) years upon return of warranty card included with your electron tube purchase.
Is there a warranty included with the 300B?
Yes. End Users receive a standard ninety (90) day warranty with each tube. If the included warranty card is filled and returned to us by post within ten (10) days of purchase, the warranty is extended to five (5) years.
What is the useful life expectancy of the 300B?
The Western Electric 300B is rated for an average life expectancy of 40,000 hours when operated within published specifications. As far as we know, no replica 300B available today comes close to this life expectancy.
Why are 300B’s engraved with a serial number?
In 1997, we introduced serial number engraving to increase traceability for both the manufacturer and customer and to further avoid counterfeit reproductions. The same number is printed on the carton seal and on a test card that contains test results for each tube. Watch the engraving and base screen printing process here.
How do newly manufactured 300B’s compare to those manufactured in the past?
Western Electric 300B’s have been and always will be manufactured in America following the original 1938 specifications. We rely on historical quality standards, proven manufacturing techniques, and decades of experience to do so. However, in a continuing effort to put quality first we have taken advantage of materials and assembly processes that were not available in the past. For example, current turbomolecular vacuum technology allows us to achieve at least two decades lower (2 x 10-6) Torr than previous runs, resulting in longer tube life. It is also easier than ever to maintain cleanroom practices for increased quality control. Additionally, most of our machinery, like our heat treatment ovens and anode presses, has been computerized for safety and efficiency. We believe our employees and ultimately our customers deserve 21st century manufacturing standards.
Though we do take advantage of modern times, some things remain the same. The 300B’s filamentary cathode core material is derived from a 1963 melt from the Western Electric Hawthorne Works in Chicago. The tooling is also original, some going back as far as 1943.
What makes the 300B so popular?
The Western Electric 300B is known for its sound quality. The magic is in its directly heated, oxide-coated filament. Though this combination is by no means unique to the 300B, the filament’s coating is. A strontium and barium mix is combined with other proprietary constituents in the ribbon to form a coating that was originally developed for use in underwater sea cable applications. We often refer to it as the secret sauce or secret formula. This special coating not only improves the lifetime of each tube, but also supports the dynamics required for superior music reproduction. As a signal is propagated through a 300B, the filament remains “hot,” never fully depleted of electrons and always at the ready. When we experience the pleasurable, water-clear sound of a 300B, we're experiencing the thermal inertia of a directly heated cathode. Learn more about the filament.