The EL34 is a thermionic

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 potential difference has been applied. The type known as ...

of the power

pentode A pentode is an electronic device having five electrodes. The term most commonly applies to a three-grid amplifying vacuum tube or thermionic valve that was invented by Gilles Holst and Bernhard D.H. Tellegen in 1926. The pentode (called a ''trip ...

type. The EL34 was introduced in 1955 by Mullard, who were owned by

Philips Koninklijke Philips N.V. (), commonly shortened to Philips, is a Dutch multinational conglomerate corporation that was founded in Eindhoven in 1891. Since 1997, it has been mostly headquartered in Amsterdam, though the Benelux headquarters is ...

. The EL34 has an

octal The octal numeral system, or oct for short, is the radix, base-8 number system, and uses the Numerical digit, digits 0 to 7. This is to say that 10octal represents eight and 100octal represents sixty-four. However, English, like most languages, ...

base (indicated by the '3' in the part number) and is found mainly in the final output stages of

audio Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to: Sound *Audio signal, an electrical representation of sound *Audio frequency, a frequency in the audio spectrum * Digital audio, representation of sou ...

amplification circuits; it was also designed to be suitable as a series regulator by virtue of its high permissible voltage between heater and cathode and other parameters. The American

RETMA tube designation The Radio Electronics Television Manufacturers' Association was formed in 1953, as a result of mergers with other trade standards organisations, such as the RMA. It was principally responsible for the standardised nomenclature for American vacuum ...

number for this tube is 6CA7. The USSR analog was 6P27S (Cyrillic: 6П27C).

Specifications

In common with all 'E' prefix tubes, using the Mullard–Philips tube designation, the EL34 has a heater voltage of 6.3 V. According to the data sheets found in old vacuum tube reference manuals, a pair of EL34s with 800 V plate voltage can produce 90 watts output in class AB1 in push–pull configuration. However, this configuration is rarely found. One application of this type was in "Australian Sound" public address amplifiers commonly used in government schools in Australia in the 1950s, using four EL34s for ≈200 watts. More commonly found is a pair of EL34s running class AB1 in push–pull around 375–450 V plate voltage and producing 50 watts output (if fixed bias is used), while a quad of EL34s running class AB1 in push–pull typically run anywhere from 425 to 500 V plate voltage and produces 100 watts output. This configuration is typically found in

guitar amplifier A guitar amplifier (or amp) is an electronic device or system that strengthens the electrical signal from a pickup on an electric guitar, bass guitar, or acoustic guitar so that it can produce sound through one or more loudspeakers, which ar ...

The EL34 is a pentode, while the 6L6, which delivers a similar range of power output, is a beam tetrode which

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 ...

referred to as a ''beam power tube''. Although power pentodes and beam tetrodes have some differences in their principles of operation (the beam forming plates of the beam tetrode or fifth electrode (3rd grid) of the pentode, both serving to hinder the return of unabsorbed electrons from the anode (or plate) to the 4th electrode (2nd grid)) and have some internal construction differences, they are functionally closely equivalent. Unlike the

6L6 6L6 is the designator for a beam power tube introduced by Radio Corporation of America in April 1936 and marketed for application as a power amplifier for audio frequencies.J. F. Dreyer Jr."The Beam Power Output Tube" New York: McGraw-Hill, ''Ele ...

, (EIA base 7AC) the EL34 has its grid 3 connection brought out to a separate Pin (Pin 1) (EIA base 8ET) and its heater draws 1.5 Amps compared to the 0.9 Amp heater in the 6L6. However, Sylvania (and possibly GE) marketed a tube as 6CA7 which was not only in a markedly different 'fat boy' envelope, but used a beam forming plate much like a 6L6. Examining the mica spacer on the top of the tube will confirm the lack of a suppressor grid. Although these tubes have similar (but not identical) characteristics, they are made very differently. Svetlana EL34 tubes

While the EL34 is no longer made by Philips, it is currently manufactured by EkspoPUL in Saratov, Russia ( Electro-Harmonix, Tung-Sol, Mullard and Genalex Gold Lion brands), JJ Electronic in Čadca, Slovakia and by Hengyang Electronics at former Foshan Nanhai Guiguang Electron Tube Factory in southern China, (Psvane and TADSales Network, brands). Some firms make a related tube called an E34L which is rated to require a higher grid bias voltage, but which may be interchangeable in some equipment.

Application

The EL34 was widely used in higher-powered audio amplifiers of the 1960s and 1970s, such as the popular Dynaco Stereo 70 and the Leak TL25 (mono) and Stereo 60, and is also widely used in high-end guitar amplifiers because it is characterized by greater

distortion In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signa ...

(considered desirable in this application) at lower power than other octal tubes such as

, KT88 or 6550. The EL34 is found in many British guitar amps and is associated with the "British tone" ( Vox, Marshall, Hiwatt, Orange) as compared to the

which is generally associated with the "American tone" ( Fender/

Mesa Boogie Mesa/Boogie (also known as Mesa Engineering) is an American company in Petaluma, California, that manufactures amplifiers and other accessories for guitars and basses. It has been in operation since 1969. Mesa was started by Randall Smith as a ...

; the earlier classic Marshall "Plexi" amps used the KT66, a beam tetrode similar to the 6L6, as well).

Replacement

* 6CA7

Similar tubes

* KT77 * 6P27S (6П27С)

References

{{Reflist
Technical specifications

* Valvo Gmbh, Valvo Taschenbuch, 1958. * RCA, RCA Receiving Tube Manual RC26, 1968.
JJ Electronics EL34 and E34L data sheet (PDF)

External links

Duncan's Amps TDSL

Reviews of EL34 tubes

Tube Data Archive, thousands of tube data sheets
Vacuum tubes Guitar amplification tubes