12AX7
| 12AX7 | |
|---|---|
RCA 12AX7
|
|
| Classification | Dual Triode |
| Service | Class-A amplifier |
| Height | 2.2 in (56 mm) |
| Diameter | 0.8 in (20 mm) |
| Cathode | |
| Cathode type | Indirectly heated |
| Heater voltage | Series / Parallel 12.6 / 6.3 |
| Heater current | Series / Parallel 150 / 300 mA |
| Anode | |
| Max dissipation Watts | 1 per section |
| Max voltage | 300 |
| Socket connections | |
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|
| Typical class-A amplifier operation | |
| Amplification factor | 100 |
| Anode voltage | 250 |
| Anode current | 1.2 mA |
| Bias voltage | -2 |
| Anode resistance | 62500 |
| References | |
| Sylvania 12AX7 datasheet | |
12AX7 (also known as ECC83) is a vacuum tube that is a miniature dual triode - 6AV6 with high voltage gain. It was developed around 1946 by RCA engineers in Camden, New Jersey, under developmental number A-4522. It was released for public sale under the 12AX7 identifier on September 15, 1947. The 12AX7 was originally intended as replacement for the 6SL7 family of dual-triode amplifier tubes for audio applications. It is popular with tube amplifier enthusiasts, and its ongoing use in such equipment makes it one of the few small-signal vacuum tubes in continuous production since it was introduced.
The 12AX7 is basically two of the triodes from a 6AV6 - a double diode triode. The 6AV6 is a miniature repackaging (with just a single cathode) of the triode and twin diodes from the octal 6SQ7 (a double-diode triode used in AM radios), which itself is very similar to the older type 75 triode-diode dating from 1930.
As of 2012[update] the 12AX7 was made in various versions by two factories in Russia (Winged C, formerly Svetlana, and New Sensor, which produces tubes under the Sovtek, Electro-Harmonix, Svetlana, Tung-Sol, and other brands for which the firm has acquired trademark rights), one in China (Shuguang), and one in Slovakia (JJ Electronic), for a total annual production estimated at two million units. The vast majority are used in new-production guitar amplifiers or for replacements in guitar and audio equipment.
The 12AX7 is a high-gain (typical amplification factor 100), low plate current triode best suited for low-level audio voltage amplification. In this role it is widely used for the preamplifier (input and mid-level) stages of audio amplifiers. It has relatively high Miller capacitance, making it unsuitable for radio-frequency use.
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