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 reciproc ...
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 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 is ...
,
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 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 a ...
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 List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...
a variant was also produced as type 6Zh32P (Russian: 6Ж32П.) EF86s were being produced in
Russia
Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eigh ...
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 g ...
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 ...
as
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).
D ...
, 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 (through a
bifilar-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 aris ...
, 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 1 ...
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 pentode
National 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