Very rare NOS NIB 1972 MULLARD Blackburn el84 6bq5 matched pair KM1 UK Philips label very strong Vox ac15 Marshall Echolette

Here for sale a very rare, perfectly matched pair of NIB British made Blackburn Mullard el84 6bq5 Km1 model with Philips label as meant for export. New and provided in original box. very close production.
Fully tested.     No issue. Super strong.

Tests results:
Tube 1 code KM1 B2F4           test result 98 %
Tube 2 code KM1 B2H1        test result 98 %

Both tubes were made in the Mullard Blackburn factory in Great Britain the same year, one tube, during the 4th week of June 1972 and the second one a bit more than 2 month later during the first week of August 1972. So super close production of this same exact KM1 model.

Declined ring getter, one round plate hole, double copper getter post, copper rods.

This pair is super strong, within NOS full specs.

For info, usually, a NOS never used Blackburn el84 usually tests within 95% and up to 102%.

   They both have very nice and super large getter flashes and absence of the typical burning marks of 60's Blackburn el84, that comes just after a very short period of use. So this shows that this pair had no use or almost no use.

Both are in top pristine condition, new unused with perfect labels and date- factory code and provided with their original Philips box.

This is real gold for a vintage Vox AC30. Do we need to present this magic sounding el84 ? They have this so rich sound, warmth and sweet unrivaled break up to die for.


I COMBINE SHIPPING ,  SO PLEASE HAVE A LOOK AT MY OTHER ITEMS AND SAVE .

These tubes has been tested with a first digital tube tester for

Heater filament test: Short circuit
Heater filament test: Open circuit
Heater filament test: Tolerance check
Heater cathode insulation: Leakage
Heater cathode insulation: Short Circuit
Tests for heater current abnormalities
Amplification factor
Voltage gain
Power gain
Screen grid test
Mutual conductance test
Dual test for double triodes
Emission
Inter electrode leakage
Inter electrode short circuit
Flash-over (arc detection, high voltage breakdown)
Gas ionisation test

And then with a second tester: my trustful Jackson 648S

  for

Leakage

Filament

Circuit

Shorts

Plate

Life test...

The Jackson 648. It is definitely one of my favorite tube testers. While it does not employ a mutual conductance test circuit, it does use an advanced emission circuit that applies separate element voltages to each tube element, and separate load circuits are also used. “These voltages and loads have been carefully selected for each tube to meet most ideally the normal operating condition of the tube.” (Source: 1950 Jackson catalog.)

In my experience, the Jackson circuitry is very effective, and often will surprise you with accuracy that approaches Hickok’s coveted “mutual conductance” test method. ( Source tubesound web site.)

I do my best to test and describe the tubes the best I can.

Note that test results may vary from one tester to an other so this must be taken as an indication, although my Jackson is regulary tested for calibration.

 Photos are part of the description you get what you see.