6V6
The 6V6 is a beam-power tetrode vacuum tube first introduced in late 1936, designed primarily for audio-frequency power amplification in the output stages of radio receivers and phonographs.[1] It utilizes a 6.3-volt, 0.45-ampere heater and delivers approximately 5 watts of power in single-ended configurations or 12 to 15 watts in push-pull arrangements, offering high efficiency and low distortion for its era.[2] With its warm, harmonically rich sound, the 6V6 has become a staple in guitar amplifiers, notably in classic Fender models such as the Champ, Princeton, and Deluxe Reverb.[3] Initially available in metal-cased and shouldered-glass envelopes, the 6V6 evolved into glass miniature variants like the 6V6GT in 1939 and the 6V6GTA with controlled warm-up features for television receivers.[4] This progression reflected advancements in vacuum tube manufacturing, enabling broader adoption in consumer audio equipment during the mid-20th century.[5] Its robust construction often exceeded published ratings, contributing to its longevity in both vintage and restored applications.[5] Electrically, the 6V6 supports a maximum plate voltage of 315 volts, screen voltage of 310 volts, and plate dissipation of 13.2 watts, with a typical amplification factor around 12.5.[5] In push-pull Class AB operation—common for audio output—it runs at a plate voltage of 315 volts and screen voltage of 236 volts, achieving 14 watts output with grid bias of -16.5 volts.[5] These parameters made it ideal for battery- or AC-powered devices requiring compact, efficient power delivery.[2] Today, the 6V6 remains in production by manufacturers including JJ Electronic, Tung-Sol, and Electro-Harmonix, often as direct equivalents like the 6V6GT or 6V6S, and is favored in high-fidelity audio systems and musical instrument amplifiers for its balanced tone and reliability.[2] New production pairs typically cost $25 to $35 as of 2025, while new-old-stock versions command $40 to $50, underscoring its enduring appeal among audiophiles and musicians.[5]History
Development and Introduction
The 6V6 vacuum tube was developed as a beam-power tetrode by RCA, with the initial glass envelope model (6V6G) introduced in late 1936. This design represented a significant advancement in power amplification for consumer electronics, building on the principles established by earlier tetrodes but optimized for broader accessibility. Early production included contributions from Ken-Rad Tube & Lamp Corporation.[1] A key innovation in the 6V6 was the incorporation of beam-forming plates, which focused the electron streams between the control grid and screen grid, thereby reducing inter-electrode capacitance and secondary electron emission while enhancing overall efficiency compared to prior power tetrodes such as the 6L6.[6] These plates allowed for lower screen grid current—typically 5-10% of plate current, versus 20% in equivalent pentodes—resulting in improved power output and reduced distortion without increasing the tube's physical footprint.[6] The 6V6's 6.3-volt filament also ensured compatibility with existing AC/DC radio circuits, facilitating its compact integration into output stages. Following its debut, the metal-cased version of the 6V6 was introduced in 1937, with production by manufacturers including RCA and Sylvania, offering enhanced durability for rugged applications while maintaining the core beam-power architecture.[5][7] By 1939, the design evolved further with the 6V6GT, which utilized an improved glass envelope for superior heat dissipation and mechanical stability, solidifying its role in audio amplification.[8] This rapid progression enabled quick adoption in radio receivers, where the tube's efficiency and size advantages addressed the demands of post-Depression era consumer devices.[9]Production and Manufacturers
The 6V6 vacuum tube was initially manufactured by Ken-Rad Tube & Lamp Corporation, with production beginning in late 1936 for civilian radio applications.[1] RCA assumed widespread promotion and large-scale manufacturing from 1937 onward, establishing the tube as a key component in consumer electronics.[9] Other major U.S. producers included Sylvania, which specialized in metal-envelope versions for improved durability, and Raytheon, which contributed to the supply chain through licensed production.[10] Production during the pre-World War II era (1936–1941) emphasized civilian markets, focusing on compact beam-power designs for home radios and early amplifiers.[11] With the onset of WWII, manufacturing shifted to meet military demands under the Joint Army-Navy (JAN) specifications, resulting in ruggedized variants like the JAN-6V6GT, which featured enhanced vibration resistance for use in portable radios and communication equipment.[12] The 6V6 was standardized as VT-107 for U.S. military applications and CV510 in British equivalents, with large quantities produced to support wartime electronics.[9] Post-war production persisted into the 1950s through companies like RCA and Sylvania, but volumes declined sharply with the transistor's rise, limiting output to niche industrial and audio uses.[9] By the late 20th century, U.S. manufacturing ceased entirely, though total historical output exceeded millions of units, reflecting the tube's ubiquity in mid-century electronics.[10] As of 2025, low-volume production continues in Eastern Europe and Asia to serve restoration projects and audiophile markets, with key manufacturers including JJ Electronic in Slovakia for reliable, high-harmonic output tubes; Electro-Harmonix (via New Sensor Corporation in Russia) for robust, plate-voltage-tolerant variants; and Shuguang in China for cost-effective recreations emphasizing traditional construction.[13][14][15]Technical Specifications
Electrical Characteristics
The 6V6 is a beam-power tetrode vacuum tube with a heater rated at 6.3 volts AC or DC and a current draw of 0.45 amperes.[16] For the 6V6GT variant, key electrical parameters include a maximum plate voltage of 350 volts, a maximum screen grid voltage of 315 volts, and a maximum plate dissipation of 14 watts.[17] The tube exhibits a transconductance of approximately 4,100 micromhos and an amplification factor (mu) of about 20-22.[18] In typical operation for the 6V6GT, the 6V6 delivers around 4.5 watts of single-ended Class A audio output power at a plate voltage of 250 volts.[16] For push-pull Class AB configurations, it provides approximately 14 watts of output at a plate voltage of 315 volts.[16] As a beam-power tetrode, the 6V6 employs beam-forming plates connected to the cathode to focus electrons into dense, ribbon-like beams, which minimizes interception by the screen grid and suppresses secondary emission without requiring a suppressor grid.[19] This design reduces screen grid current to about 5-10% of the plate current—roughly half the 20% typical in standard tetrodes—while enabling higher overall efficiency of approximately 25% compared to conventional tetrodes.[19] In push-pull operation, the power output per tube can be approximated by the formula: P_\text{out} \approx \frac{V_\text{plate} \times I_\text{plate} \times \eta}{2} where V_\text{plate} is the plate voltage, I_\text{plate} is the plate current, and \eta is the efficiency.[19] The 6V6 demonstrates good linearity for audio applications, with typical total harmonic distortion below 5% at rated output levels, and it supports a frequency response from 20 Hz to 20 kHz.[20]| Parameter | Single-Ended Class A (Typical, 6V6GT) | Push-Pull Class AB (Typical, 6V6GT) |
|---|---|---|
| Plate Voltage | 250 V | 315 V |
| Screen Voltage | 250 V | 250 V |
| Grid Bias | -12.5 V | -16.5 V |
| Zero-Signal Plate Current | 45 mA | 36 mA (per tube) |
| Output Power | ~4.5 W | ~14 W |