12AX7 (also known as ECC83) is a miniature dual-
triode
A triode is an electronic amplifying vacuum tube (or ''valve'' in British English) consisting of three electrodes inside an evacuated glass envelope: a heated filament or cathode, a grid, and a plate (anode). Developed from Lee De Forest's 19 ...
6AV6 vacuum tube
A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied.
The type kn ...
with high voltage
gain
Gain or GAIN may refer to:
Science and technology
* Gain (electronics), an electronics and signal processing term
* Antenna gain
* Gain (laser), the amplification involved in laser emission
* Gain (projection screens)
* Information gain in de ...
. Developed around 1946 by
RCA
The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Comp ...
engineers
in
Camden, New Jersey
Camden is a city in and the county seat of Camden County, in the U.S. state of New Jersey. Camden is part of the Delaware Valley metropolitan area and is located directly across the Delaware River from Philadelphia, Pennsylvania. At the 2020 ...
, 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. As a popular choice for guitar tube amplifiers, its ongoing use in such equipment makes it one of the few small-signal vacuum tubes in continuous production since it was introduced.
History
The 12AX7 is a twin triode basically composed of 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.
Application
![TriodeECC83Characteristic1](https://upload.wikimedia.org/wikipedia/commons/d/d8/TriodeECC83Characteristic1.png)
The 12AX7 is a high-gain (typical amplification factor 100), low-plate-current
triode
A triode is an electronic amplifying vacuum tube (or ''valve'' in British English) consisting of three electrodes inside an evacuated glass envelope: a heated filament or cathode, a grid, and a plate (anode). Developed from Lee De Forest's 19 ...
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
A miller is a person who operates a Gristmill, mill, a machine to grind a grain (for example corn or wheat) to make flour. Mill (grinding), Milling is among the oldest of human occupations. "Miller", "Milne" and other variants are common surname ...
capacitance, making it unsuitable for radio-frequency use.
Typically a 12AX7 triode is configured with a high-value plate resistor, 100 kohms in most guitar amps and 220 kΩ or more in high-fidelity equipment. Grid bias is most often provided by a cathode resistor. If the cathode resistor is unbypassed, negative feedback is introduced and each half of a 12AX7 provides a typical voltage gain of about 30; the amplification factor is basically twice the maximum stage gain, as the plate impedance must be matched. Thus half the voltage is across the tube at rest, half across the load resistor. The cathode resistor can be bypassed to reduce or eliminate AC negative feedback and thereby increase gain; maximum gain is about 60 times with a 100k plate load, and a center biased and bypassed cathode, and higher with a larger plate load.
Where
= voltage gain,
is the amplification factor of the valve,
is the internal plate resistance,
is the cathode resistor and
is the parallel combination of
(external plate resistor) and
. If the cathode resistor is bypassed, use
.
The initial “12” in the designator implies a 12-volt heater requirement; however, the tube has a center-tapped heater so it can be used in either 6.3-V or 12.6-V heater circuits.
Similar twin-triode designs
The 12AX7 is the most common member of what eventually became a large family of twin-triode vacuum tubes, manufactured all over the world, all sharing the same pinout (EIA 9A). Most use heaters which can be optionally wired in series (12.6V, 150 mA) or parallel (6.3V, 300 mA). Other tubes, which in some cases can be used interchangeably in an emergency or for different performance characteristics, include the
12AT7
12AT7 (also known in Europe by the Mullard–Philips tube designation of ECC81) is a miniature 9-pin medium-gain (60) dual-triode vacuum tube popular in guitar amplifiers. It belongs to a large family of dual triode vacuum tubes which share the ...
,
12AU7
The 12AU7 and its variants are miniature nine-pin (B9A base) medium-gain dual triode vacuum tubes. It belongs to a large family of dual triode vacuum tubes which share the same pinout (RETMA tube designation, RETMA 9A). 12AU7 is also known in Eur ...
,
12AV7, 12AY7, and the low-voltage 12U7, plus many four-digit EIA series dual triodes. They span a wide range of voltage gain and transconductance. Different versions of each were designed for enhanced ruggedness, low
microphonics
Microphonics, microphony, or microphonism describes the phenomenon wherein certain components in electronic devices transform mechanical vibrations into an undesired electrical signal (noise). The term comes from analogy with a microphone, which ...
, stability, lifespan, etc.
Those other designs offer lower voltage gain (traded off for higher plate current) than the 12AX7 (which has a voltage gain or
of 100), and are more suitable for high-frequency applications.
Some American designs similar to the 12AX7:
* 12AD7 (October 10, 1955 - 225mA heater - low hum)
*
12AT7
12AT7 (also known in Europe by the Mullard–Philips tube designation of ECC81) is a miniature 9-pin medium-gain (60) dual-triode vacuum tube popular in guitar amplifiers. It belongs to a large family of dual triode vacuum tubes which share the ...
(May 20, 1947, dual 6AB4,
= 60)
*
12AU7
The 12AU7 and its variants are miniature nine-pin (B9A base) medium-gain dual triode vacuum tubes. It belongs to a large family of dual triode vacuum tubes which share the same pinout (RETMA tube designation, RETMA 9A). 12AU7 is also known in Eur ...
(October 18, 1946, dual 6C4,
= 17-20)
* 12AV7 (February 14, 1950 - dual 6BC4,
= 37-41)
* 12AX7 (September 15, 1947 - dual 6DR4, also like octal 6SL7,
= 100) dual 12AV6 (6AV6)
* 12AY7 (December 7, 1948 -
= 44, for audio preamp use)
* 12AZ7 (March 2, 1951 - 225mA heater,
= 60)
* 12DF7 (
= 100, low microphonics)
* 12DT7 (
= 100)
* 12DW7 (First triode:
= 100, Second triode:
= 17)
* 12U7 (
= 20, for use in automotive radios on 12-volt plate supply)
Although commonly known in Europe by its
Mullard–Philips tube designation In Europe, the principal method of numbering vacuum tubes ("thermionic valves") was the nomenclature used by the Philips company and its subsidiaries Mullard in the UK, Valvo( de, it) in Germany, Radiotechnique (''Miniwatt-Dario'' b ...
of ECC83, other European variations also exist including the low-
noise
Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference arise ...
versions 12AX7A, 12AD7, 6681, 7025, and 7729; European versions B339, B759, CV492, CV4004, CV8156, CV8222, ECC803, ECC803S, E2164, and M8137; and the lower-gain low-noise versions 5751 and 6851, intended for avionics equipment.
In European usage special-quality valves of some sort were often indicated by exchanging letters and digits in the name: the E83CC was a special-quality ECC83.
In the US a "W" in the designation, as in 12AX7WA, designates the tube as complying with military grade, higher reliability specifications.
The 'E' in the European designation classifies this as having a 6.3 volt heater, whereas the American designation of 12AX7 classifies it as having a 12.6 volt heater. It can, of course, be wired for operation off either voltage.
Manufacturers
versions of the 12AX7/ECC83 are available from the following manufacturers:
* In
Russia
Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...
:
New Sensor, which produces tubes under the
Sovtek
Sovtek is a brand of vacuum tube owned by Mike Matthews's New Sensor Corporation and manufactured in Saratov, Russia. They are often used in guitar Guitar amplifier, amplification and include versions of the popular 12AX7, EL84, EL34, and 6L6 vacuu ...
,
Electro-Harmonix
Electro-Harmonix (also commonly referred to as EHX) is a New York City-based company that makes electronic audio processors and sells rebranded vacuum tubes. The company was founded by Mike Matthews in 1968. It is best known for a series of gu ...
, Svetlana,
Tung-Sol
Tung-Sol was an American manufacturer of electronics, mainly lamps and vacuum tubes.
History
Tung-Sol was founded as Tung-Sol Lamp Works Inc. in Newark, New Jersey in 1907. Their early products were mainly geared towards the automotive market ...
, and
Mullard
Mullard Limited was a British manufacturer of electronic components. The Mullard Radio Valve Co. Ltd. of Southfields, London, was founded in 1920 by Captain Stanley R. Mullard, who had previously designed thermionic valves for the Admiral ...
brands
* In
Slovakia
Slovakia (; sk, Slovensko ), officially the Slovak Republic ( sk, Slovenská republika, links=no ), is a landlocked country in Central Europe. It is bordered by Poland to the north, Ukraine to the east, Hungary to the south, Austria to the s ...
:
JJ Electronic
JJ Electronic, s.r.o is a Slovak electronic component manufacturer, and one of the world's remaining producers of vacuum tubes. It is based in Čadca, in the Kysuce region of Slovakia.
Most of its products are audio receiving tubes, mainly used f ...
(annual production of approximately two million units)
* In
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
:
Hengyang Electronics, Tubes sold under Psvane and TAD brand names. Company owns its independent manufacturing facility in Southern China (former Guiguang tube factory) and recently they acquired former small signal tube manufacturing line from Tianjin Quanzheng factory (TJ Full Music)
[About Linlai Team,]
Gallery
File:Electro-harmonix 12AX7EH.JPG, Electro-Harmonix 12AX7EH
File:ECC83 var.jpg, Various brands of 12AX7, with measuring tape to indicate size
File:Dubulttriode darbiibaa.jpg, Tungsram ECC83 during operation
File:Philips 12AX7WA tube.jpg, Philips JAN 12AX7WA (Joint Army Navy)
See also
*
List of vacuum tubes
This is a list of vacuum tubes or ''thermionic valves'', and low-pressure gas-filled tubes, or ''discharge tubes''. Before the advent of semiconductor devices, thousands of tube types were used in consumer electronics. Many industrial, military or ...
References
External links
Duncan's Amps TDSL.Reviews of 12ax7 tubes.The 12AX7 tube.12AX7/ECC83 page(wit
datasheet a
JJ Electronic
{{DEFAULTSORT:12ax7
Vacuum tubes
Guitar amplification tubes
RCA