Amp books
http://ampbooks.com/home/tutorials/pentode-tutorial-1/
Multiple discussions of pentode preamps -- guitar orientation.
http://www.pmillett.com/pentode_phono_preamp.htm
Nice article about a custom pentode design.
Very nice pentode design using the D3A (7721?)
http://www.audiodesignguide.com/Phono/pre-phono4.html
Tuesday, October 4, 2011
Alternatives to EF86
EF806S/6267/EF86 are the same tube electrically and pin compatible, EF40 is the predecessor that uses a 8pin rim-lock socket. E80F is pin compatible, has slightly less slope and g2g1 mu is 25 (EF86 is 38). this tube appears to be electrically similar to the 5879. EF83 (6BK8) is pin compatible to EF86, however, it is a vari-mu tube. NOTE: shady fleabay sellers are trying to pawn these off as an EF86 replacement. they are NOT an EF86, as the EF 86 is a sharp cut-off pentode.E804S - electrically similar to EF86 with different noval pinning with slightly less filament draw. it is a hi-reliability long-life tube.EF85 electrically similar characteristics to the 6AU6 in noval pinning. EF94 is electrical and pin equivalent to the 6AU6.Brimar 6BR7 seem to be nice AF tube, electrically similar to EF86, but is not pin compatible. still obtainable for reasonable (~15USD) scratch.
Source is Reply 15 to note 11804 in el34 world.
http://www.el34world.com/Forum/index.php?topic=11804.0
Source is Reply 15 to note 11804 in el34 world.
http://www.el34world.com/Forum/index.php?topic=11804.0
Mullard EF86 -- Description
Note about Mullard EF86 tube.
http://www.blogger.com/home?pli=1
The following is taken from a leaflet entitled `Mullard world series valves for audio equipment' it probably dates from the early 1960s.
A high gain pentode of special design, the EF86 is particularly suitable for preamplifier and input stages, in which hum, noise and microphony must be kept to a minimum. The low frequency noise generated by the valve is equivalent to a voltage of 2 μV on the control grid for a bandwidth from 25 to 10,000 Hz.
The electrode structure has been made particularly rigid to keep the microphony of the valve to a very low level. There are no appreciable internal resonances below 1000 Hz, the vibration at higher frequencies being effectively damped out by the chassis and the valveholder.
Hum is kept to a minimum by winding the heater as a bifilar twisted pair of wires, with the magnetic field of the one wire opposed to that of the other. Effective internal screening reduces the internal valve capacitances through which hum can be transferred to the signal electrodes. The screening also shields the electrode structure from the alternating fields set up by transformers, etc., which otherwise would induce mains frequency AC in them.
http://www.blogger.com/home?pli=1
The following is taken from a leaflet entitled `Mullard world series valves for audio equipment' it probably dates from the early 1960s.
A high gain pentode of special design, the EF86 is particularly suitable for preamplifier and input stages, in which hum, noise and microphony must be kept to a minimum. The low frequency noise generated by the valve is equivalent to a voltage of 2 μV on the control grid for a bandwidth from 25 to 10,000 Hz.
The electrode structure has been made particularly rigid to keep the microphony of the valve to a very low level. There are no appreciable internal resonances below 1000 Hz, the vibration at higher frequencies being effectively damped out by the chassis and the valveholder.
Hum is kept to a minimum by winding the heater as a bifilar twisted pair of wires, with the magnetic field of the one wire opposed to that of the other. Effective internal screening reduces the internal valve capacitances through which hum can be transferred to the signal electrodes. The screening also shields the electrode structure from the alternating fields set up by transformers, etc., which otherwise would induce mains frequency AC in them.
Subscribe to:
Posts (Atom)