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Mullard EL34 6CA7 Single Halo Xf3 Matched Pair
MULLARD EL34 6CA7 MATCHED PAIR O HALO BLACKBURN XF2
The Legendary 1960's EL34 "Xf3" by Mullard, Blackburn, U.K.
The World's most musical EL34 tube known for it's pronounced liquid midrange.
Amplitrex Digital tested and plate matched for your musical pleasure
Selected for Uniquely Matched Plate-Resistance (Rp) & Tube-Gain (Mu)!
..." This tube is known for excellent performance, incredible bottom end, pronounced liquid midrange, outstanding highs. Described as the most musical sounding EL34 in the world, one of the most rugged longest lasting EL34's ever made, recently imitated but never equaled, clean, and powerful. These 1960's legends have a super polished and quite refined bass, midrange, top end. A Major improvement over other 6CA7's. Get rid of those Chinese or Russian 6CA7's and UPGRADE to original Mullard U.K. power tubes - which are Superior by far to Svetlana or Sovtek re-issue EL34's"...
PRICE IS FOR 2 BALANCED & MATCHED TUBES Mullard EL34 Xf3 Matched Pair
ALL PICTURES OF THE ACTUAL TUBES YOU WILL RECEIVE
MATCHED PAIR with O Getters TUBE MUSEUM QUALITY STRONG LEGENDARY BLACKBURN U.K. POWER TUBES
LOW-NOISE - BEAUTIFUL SOUNDING - 1960's RARE MADE IN U.K. AUDIO TUBES
TWO (2) of the Rare Mullard U.K. Blackburn Xf3 Production, with Sweet sounding O-Getters! Very Compelling Musical Tone with Long 10,000 Hour Heater Life!
These twin top-mica shields are designed to "deflect" unwanted electron bombardment to prevent cathode-poisioning. They work as a deflector-shield and help the tube achieve its correct operation point and last longer and operate cooler.
Recommended for:
Conrad Johnson
Dynaco ST-70
Vox
Park
HiWatt
Matchless
Marshall JTM combo 50 watts 1978
Marshall "Plexi"
Fender Amps
Musicman
These tubes are "PROFESSIONAL SPECIAL QUALITY" Premium Quality Amplitrex Digitally Tested Audio tubes
Authentic Mullard el34 Xf3 MADE in the U.K. in the 1964
NOS WITH PERFECT MATCHING mA Plate Current of 34.4mA and 34.4mA! ACTUAL AMPLITREX TUBE-MUSEUM-DIGITAL-PROOF IN PICTURES!
ou simply can not find ANYWHERE a Matched Pair with IDENTICAL Emissions ANYWHERE!
It's to just a claim - It's AMPLITREX "DIGITAL-PROOF" AS DISPLAYED IN THE ACTUAL PHOTOGRAPHS! Take a look - you'll be AMAZED!
TESTS BETTER THAN 100% NOS Gm
IDENTICAL MATCHED mA (emissions)
tube 1: 34.4mA and 6,210 Gm (141%) @ 450 Plate Volts
tube 2: 34.4mA and 6,110 Gm (138%) @ 450 Plate Volts
4,400 Gm= 100% NOS Factory recommended specification @ 450V!
Tube Museum Quality
Xf3 MULLARD UNITED KINGDOM
NOS "SIEMENS LOGO"
PROFESSIONAL SINGLE-O-GETTERS
EL34 = 6CA7
RARE VALVE AUDIO POWER TUBES
The older MULLARD SINGLE "O" GETTER EL34 TUBES were finest Professional Power Tubes MULLARD or any manufacturer ever made! THESE HAVE BEEN HORDED BY PROFESSIONAL AUDIOPHILES AND ARE NEVER SEEN ANYMORE, ESPECIALLY TODAY! THESE ARE THE BEST SOUNDING, BEST MADE and MOST VALUABLE and RARE out of ALL the 6CA7 Amp and Audio tubes. You won't find other Extremely RARE MULLARD "Tube Museum Certified" tubes around - that's because they are kept and treasured by those who know which the BEST EL34 tubes are!
MATCHING MULLARD DATE CODES!
Xf3 B4B2 and Xf3 B4C2
Would you feed yourself without knowing the ingredients? Of course not, so don't feed your preamp a tube not knowing the complete specifications!
Here we have an excellent example of the finest EL34 low-noise MATCHED mA tubes. >100% Gm
TESTED @ 450 PLATE-VOLTS
To match tubes by transconductance, first make sure that the emission is within 10% for the tubes.
Then compare transconductance (Gm) readings between tubes for a 10% or better match.
These are a 1.5% match in transconductance (Gm)! Much Much LESS than the required 5% RULE!
In fact, almost insignificant, might as well be "TWINS" !!!!!
tube 1: 34.4mA and 6,210 Gm (141%) @ 450 Plate Volts
tube 2: 34.4mA and 6,110 Gm (138%) @ 450 Plate Volts
IT'S VERY RARE TO FIND IDENTICALLY mA MATCHED EL34's
Here we have a PERFECT MATCH example of 34.4mA and 34.4mA
To match tubes by emission, The Tube Museum uses the Fixed Bias Mode, and compare the resulting plate currents measured during the test. The closer the values, the better the match. In push-pull power output stages, the emission match should be within 10% if there is no DC balance control or separate bias adjustment for each tube. Even with these adjustments, closely matching the emission of each tube greatly improves performance and long-term reliability.
4,400 Gm= 100% NOS Factory recommended specification @ 450V!
Actual tubes were tested on the State-of-the-Art Tube Museum Certified Tube Test System
CERTIFIED LOW-NOISE SPECIMENS
TubeMuseum tested tubes takes the guesswork out of the process of selection delivering you the best Audio tubes that there possibly can be.
MATCHING TUBES at the TUBE MUSEUM:
Vacuum tubes can be matched for use in balanced circuits, such as push-pull output or fully-differential preamplifier use. Single-section tubes can be matched to each other, and dual section tubes can have their sections matched as well as establishing a match between tubes.
Tube matching generally consists of testing a number of identical tubes, and then grouping them by one or more tested parameters. Tubes can be matched by emission, transconductance, or both. If only one parameter is to be matched, it is recommended that emission is selected.
For power output tubes, some amplifiers have DC and AC balance controls. These controls can null out some of the variance in tube parameters. In parallel (SEP) and push-pull parallel power tube operation, close matching is essential for maximum performance. There are generally no separate bias and drive controls when tubes are run in parallel, and if the tubes don't share the AC and DC loads symmetrically, power output and distortion will suffer greatly.
Differential audio and instrumentation amplifiers achieve best performance when matched tubes are used. Quite often, miniature dual triodes are employed. These can have their sections matched, or all the tubes in a signal chain can be matched. The circuit topology dictates which is more important, but full matching for this type of equipment guarantees best performance. To match tubes by emission, The Tube Museum uses the Fixed Bias Mode, and compare the resulting plate currents measured during the test. The closer the values, the better the match. In push-pull power output stages, the emission match should be within 10% if there is no DC balance control or separate bias adjustment for each tube. Even with these adjustments, closely matching the emission of each tube greatly improves performance and long-term reliability.
To match tubes by transconductance, first make sure that the emission is within 10% for the tubes. Then compare transconductance readings between tubes for a 5% or better match. For preamplifier tubes, emission and transconductance matching can also improve performance. Particularly in long tail pair phase splitter operation, the tubes or tube sections should be closely matched. If the phase splitter is operating as symmetrically as possible, distortion will be reduced, and drive to the output stage will increase.
Sometimes there are driver tubes after the phase splitter but before the output tubes. These tubes should also be matched, so that drive to the outputs remains as symmetrical as possible throughout the signal path.
Fully differential preamplifiers often used in the recording industry will be push-pull from input to output transformers. Keeping things balanced throughout the signal path is essential to take advantage of the wide bandwidth, low noise and low distortion this equipment is capable of.
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