Mullard 6CA7/EL34 Blackburn production pr. fully tested

This listing is for a gently used pr.of Mullard GT. Britain/Blackburn manufactured EL34 vacuum tubes. These tubes have identical internal construction with two copper support rods supporting a single medium sized halo getter. There are two winged fins below the getter in each tube. These tubes were tested in a calibrated Heathkitt TT-1A mutual conductance tube tester and tested way above 100% NOS, nearly pegging the meter during the tests. These tube have approximately 100 hours of total use as voltage regulators in the outboard power supply of an Antique Sound Lab twin Head 2A3 preamplifier. These are rated at 10,000 hours of useful life, so they are almost in new condition. Unfortunately, long ago one of the guide pins broke off one of the EL34’s. This in no way compromises the tubes performance and it’s easy to see the correct orientation when placing the tube in a socket. These tubes come in the original G.E. boxes. A small amount of the white GE logo is still visible on one tubes. The tube with the good guide pin has no lettering at all, just a barely visible Blackburn production code. The " 5 " grading is due to the broken guide pin and the lack of visible lettering one one of the tubes. The tubes perform perfectly and have excellent chrome flashing!  

The 6CA7/EL34 vacuum tube is a high transconductance Pentode that normally measures far above the 0 - 3,000 uMhos scale on the Heathkit TT-1A, therefore a multiplication factor of 5 is stated in the tube roll chart when testing this tube to obtain the actual transconductance of the tube.

Test results:
Tube 1 has guide pin (date code: B9B)
2,850 x 5 = 14,250 uMhos


Tube 2 white lettering visible, w/broken guide pin (date code: Df2)
2,900 x 5 = 14,500 uMhos

Nos 100% =  11,000 uMhos
R.P. reject point (65% of new spec) = 7,150 uMhos


Please note that I only accept Pay Pal for all Audiogon transactions. No International deliveries are allowed for this item. USPS Priority Mail to any USA destination is $8.00 for this pair of Mullard EL34’s. I will also be selling the Amperex/H.P. branded 6DJ8 "D" gold pins and RCA 2A3 tubes from the ASL Twin Head in other Audiogon listings.