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 recipro ...
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 ''tri ...
vacuum tube
A vacuum tube, electron tube, thermionic 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. It ...
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. (), simply branded Philips, is a Dutch multinational health technology company that was founded in Eindhoven in 1891. Since 1997, its world headquarters have been situated in Amsterdam, though the Benelux headquarter ...
,
Mullard
Mullard Limited was a British manufacturer of electronics, 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 (US ...
,
Telefunken
Telefunken was a German radio and television producer, founded in Berlin in 1903 as a joint venture between Siemens & Halske and the ''AEG (German company), Allgemeine Elektrizitäts-Gesellschaft'' (AEG) ("General electricity company").
Prior to ...
, 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, with low noise and low
microphony claimed advantages, although a rubber-mounted vibration-resistant base was still recommended.
It has a 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
High fidelity (hi-fi or, rarely, HiFi) is the high-quality reproduction of sound. It is popular with audiophiles and home audio enthusiasts. Ideally, high-fidelity equipment has inaudible noise and distortion, and a flat (neutral, uncolored) ...
development. An industrial tube variant is known as 6267. In the former
Soviet Union
The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
a variant was also produced as type 6Zh32P (Russian: 6Ж32П.) EF86s were being produced in
Russia
Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...
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, officially the Slovak Republic, 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 west, and the Czech Republic to the northwest. Slovakia's ...
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, Voltage#Galvani potential vs. electrochemical potential, electric potential difference (voltage), and electromotive force in the International System of Units, International System of Uni ...
, 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 the:
*
Hum (through a
bifilar-wound twisted pair of heater wires),
*
noise
Noise is sound, chiefly unwanted, unintentional, or harmful sound considered unpleasant, loud, or disruptive to mental or hearing faculties. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrat ...
, 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 amplifier, amplifying vacuum tube (or ''thermionic valve'' in British English) consisting of three electrodes inside an evacuated glass envelope: a heated Electrical filament, filament or cathode, a control grid, grid ...
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
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{{Webarchive, url=https://web.archive.org/web/20061109155707/https://www.tubeworld.com/6267.htm , date=9 November 2006
TDSL Tube data: EF86Datasheet for Thorn/Mazda 6F22/EF86 (pdf)
Vacuum tubes
Guitar amplification tubes