The EF86 is a high

transconductance Transconductance (for transfer conductance), also infrequently called mutual conductance, is the electrical characteristic relating the current through the output of a device to the voltage across the input of a device. Conductance is the reciproca ...

sharp cutoff

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 ''tripl ...

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 Noval (B9A) base for

audio-frequency An audio frequency or audible frequency (AF) is a periodic vibration whose frequency is audible to the average human. The SI unit of frequency is the hertz (Hz). It is the property of sound that most determines pitch. The generally accepted ...

applications. It was introduced by the Mullard company in 1953 and was produced 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 i ...

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 ...

Telefunken Telefunken was a German radio and television apparatus company, founded in Berlin in 1903, as a joint venture of Siemens & Halske and the ''Allgemeine Elektrizitäts-Gesellschaft'' (AEG) ('General electricity company'). The name "Telefunken" app ...

, Valvo, and GEC among others. It is very similar electrically to the octal base EF37A and the Rimlock base EF40. Unlike many pentodes it was designed specifically for audio applications, low noise and low

microphony 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, whic ...

being claimed advantages, although a rubber-mounted vibration-resistant base was still recommended. It has much higher stage gain than any triode, which makes it susceptible to microphony. The EF86 was used in many

preamplifier A preamplifier, also known as a preamp, is an electronic amplifier that converts a weak electrical signal into an output signal strong enough to be noise-tolerant and strong enough for further processing, or for sending to a power amplifier an ...

designs during the last decades of vacuum tube hi-fi development. An industrial variant of the tube is known as 6267. In the former

Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...

a variant was also produced as type 6Zh32P (Russian: 6Ж32П.) EF86s were being produced 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 ...

in two versions under the

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 ...

brand and in the

Slovak Republic 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 ...

(formerly Tesla).

Characteristics

6.3

Volt The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827). Defi ...

, 200 mA indirectly-heated A.F. miniature pentode with Noval (B9A) base with an EIA 9CQ (or 9BJ) basing diagram. * Transconductance: 2.2 mA/V at I_a=3.0 mA, I_g2=0.6 mA, V_a=250 V, V_g1=-2.2 V, V_g2=140 V, V_g3=0 V * Voltage gain: 185 (45 dB) at V_supply=250 V, I_k=0.9 mA, R_k=2.2 kilohm, R_a=220 kilohm, R_g1=1 megohm, Vout<44 V_RMS Special precautions have been taken in the design to reduce: *

Hum Hum may refer to: Science * Hum (sound), a sound produced with closed lips, or by insects, or other periodic motion * Mains hum, an electric or electromagnetic phenomenon * The Hum, an acoustic phenomenon * Venous hum, a physiological sensation ...

(through a

bifilar A bifilar coil is an electromagnetic coil that contains two closely spaced, parallel windings. In engineering, the word ''bifilar'' describes wire which is made of two filaments or strands. It is commonly used to denote special types of winding ...

-wound twisted pair of heater wires), *

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 ...

, and * microphony (through a rigid internal structure to reduce resonances). The EF86 is much less noisy than other pentodes, but slightly noisier than some

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 ...

s at about 2 µV equivalent input noise to 10 kHz. Although used in circuits such as tape recorder input stages and instrument amplifiers, microphony can be a problem, even when mounted in a vibration-reducing valve holder.

Equivalent and similar devices

* 6267 * Z729 * CV2901 * 6BK8 * 6CF8 * 6F22 * CV8068 * CV10098 Special quality: * EF86SQ * M8195 * CV4085 * EF806S Different heater requirements: * PF86, 300 mA (4.5 V) * UF86, 100 mA (12.6 V) The rarely used EF83 is a remote-cutoff pentodeNational Valve Museum: EF83
/ref> otherwise similar to the EF86; the remote cutoff (variable mu) makes it suitable for applications such as

automatic gain control Automatic gain control (AGC) is a closed-loop feedback regulating circuit in an amplifier or chain of amplifiers, the purpose of which is to maintain a suitable signal amplitude at its output, despite variation of the signal amplitude at the inpu ...

(agc) in tape recorders.

References

External links

Tubeworld.com's EF86 page

TDSL Tube data: EF86

Datasheet for Thorn/Mazda 6F22/EF86 (pdf)
Vacuum tubes Guitar amplification tubes