The original Western Electric 300B vacuum tube – Five(5) Year Warranty
What if the best sound was achieved decades ago? In 1938, Western Electric manufactured the first type 300B electron tube. It was a breakthrough power triode, but in those days it hummed away from behind a curtain in early Hollywood sound systems. The same things that served moviegoers back then—low noise, ultra-long life, sonic purity and warmth—made it a standout tube for music lovers and vintage audio collectors as the years passed. Deep into the age of the transistor, communities around the world in search of true, original, high-fidelity sound rediscovered the 300B and its exceptional performance. New amplifier designs brought the tube front and center, its customary yellow lettering on proud display.
Today, the Western Electric 300B is manufactured at the Rossville Works. Our new factory home was custom-built to master the dozens of individual demands of tube making, from sealing the iconic glass bulb to the complex metallurgic processes within. We’ve modernized the production line here and there to establish forward momentum at a company with 150 years of history. Western Electric believes twenty-first century listeners deserve twenty-first century manufacturing standards.
The WE 300B sound is balanced, powerful and refined with quality bass from the lowest frequencies through the upper bass. The midrange above is a thing of beauty; dulcet tones, seductive vocals, instruments of all types dimensional and present, all heightening the participatory elements of music.
High frequencies are at once transparent, lovely, sweet, burnished and beautifully seductive. The air and space between performers are extraordinary, performers appear on a quiet and focused soundstage whose width and depth are masterfully rendered. You don’t have to search to find the sweet spot with a WE 300B amplifier, it’s all around you.
Find out what tube aficionados all over the globe know, the WE 300B is the most natural, elegant and emotive triode anywhere in the known universe.
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.
(Ef = 5.0 volts, a.c., Eb = 300 volts and Ec = -61 volts)
Plate current 60 milliamperes
Amplification factor 3.85
Plate resistance 700 ohms
Grid to plate transconductance 5500 micromhos
Limiting Operating Conditions for Safe Operation
(Not simultaneous ratings)
Maximum plate voltage: 450 volts
Maximum plate dissipation: 40 watts
Maximum plate current of an average tube for fixed grid bias: 70 milliamperes
Maximum plate current for manually adjusted grid bias or self-biasing circuit: 100 milliamperes
Recommended Operating Conditions
Recommended and maximum conditions for alternating-current filament supply are given in the table. Recommended conditions or others of no greater severity should be selected in preference to maximum conditions wherever possible. The life of the tube at maximum operating conditions will be shorter than at the recommended conditions.
Where it is necessary to operate the tube at or near the maximum plate current of 100 milliamperes, provision should be made for adjusting the grid bias of each tube independently, so that the maximum safe plate current will not be exceeded in any tube. Alternatively, a self-biasing circuit may be used, in which the grid bias for the tube is obtained from the voltage drop produced by the plate current of that tube flowing through a resistance.
Where it is necessary to use a fixed grid bias, the plate current of the average tube should be limited to a maximum value of 70 milliamperes, so that tubes having plate currents higher than the average will not exceed the maximum safe plate current.
Power Output and Distortion
Performance data including power output, second and third harmonic levels for a number of operating conditions are given in the table.
The variation of power output and harmonic levels with load resistance for several values of operating plate current is shown in Figures 7, 8 and 9, for a plate voltage of 350 volts.
The peak value of the sinusoidal input voltage, Egm, which gives the indicated power output, Pm and harmonic levels, F2m and F3m for each point in both the curves and the table, is numerically equal to the grid biasing voltage at that point. For a smaller input voltage Eg, the approximate levels may be computed from the following relations.
Plate-current characteristics for a typical tube are shown in Figure 3 as functions of grid bias, for alternating-current filament supply. The corresponding amplification-factor, plate-resistance, and transconductance characteristics are given in Figures 4, 5 and 6, respectively. When direct-current filament supply is used, and the grid and plate returns are connected to the negative end of the filament, the same characteristics are applicable if 3.5 is subtracted from the numerical value of each grid bias.
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.
How are 300B’s matched? Why are matched sets offered?
All pairs and quad sets are computer-matched based on a range of performance characteristics. We capture this data during final inspection and use it during order fulfillment to identify eligible pairs.
Offering tubes that are as close to identical as possible gives the end user confidence. To ensure optimal music playback, end users put great effort into balancing each component that carries the audio signal. A matched set of Western Electric 300B vacuum tubes—when operated within the published specifications with a good amplifier—will never interrupt that “balance.” This is particularly important in push-pull configurations.
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 filament 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.
I am seeing a blue glow inside my 300B. Does this affect normal operation? Does this effect mean my tube is defective?
A blue glow may appear in the dome of the WE300-B just below the upper mica and the top edge of the plate. The space between the plate and glass is small at this point (less than 1/8”) and appears to be the only area of the tube where this phenomenon takes place. The glow is caused by the electrons striking the plate, volatizing the surface, and dislodging atoms of nickel. High speed barium-strontium electrons from the filament collide with the atom, tearing off electrons, ionizing them and causing a deep blue color even in a well evacuated tube. The resulting glow is a function of the plate voltage and the number of gas molecules in the envelope. In a good vacuum there are still billions of molecules. The electrons travel safely back to the positively charged plate.
The size of the glow varies with plate voltage and is not the same for each tube and can range from hardly discernible to very obvious, even in daylight. It does not affect tube performance as can be shown by observing the characteristic curves during tube operation.
However, dangerous levels of gas can ionize throughout the entire bulb from a high voltage spark. In this case, the gas will be pink in color and will cause variations in plate current. Air in the tube can ionize in a similar manner throughout the entire bulb, but will appear more blue than pink. In this case, the filament becomes oxidized and emission will drop dramatically.