Description

MATCHED PAIR E88CC =6922 SIEMENS GRAY SHIELD HOLY GRAIL -MUNICH USED TESTED NOS . These tubes are matched by curves and by gain. Buyer will receive the exact tube seen in photos . The tubes were tested in a professional laboratory with one of the best performing Tube Testers available at the moment: ROETEST V10, and the results of the parameters can be seen in the attached PDFs. According to the tube codes, they were produced in the 60s The tubes have code:A4 9K & A4 A0 Tube nr.6 Transconductance ( GM): 12.99/13.16 mA/V - 104%/105%- (100% = 12.50 mA/V) P late current ( IA): 15.343/15.268 mA - 102% / 102% - (100% = 15 mA) Tube nr.7 Transconductance ( GM): /12.63 /12.05 mA/V - 101%/97 % (100% = 12.50 mA/V) Plate current (IA): 15.26/14.263 mA - 102%/95% -(100% = 15 mA) NO shorts, leakage or gas . The Gain parameters is Tub nr.6 μ=32.7 μ=32.7 Tub nr.7 μ=32.7 μ=32.7 Tested with Roetest V10, "the Rolls Royce of tube testers" [emissionlab quote], a wonderful german professional system for testing tubes, it shows everything about a tube. You are looking at a matched pair of NOS E88CC , best selected by curves using Roetest V10 professional tube testing system, the best tube tester that exists now, a wonderful device. If you have experience in the field of tubes you can find in the photos and in the details below the testing / sorting procedure and all the results, and if you do not have the necessary experience to understand what is explained you can trust that we deliver only very good tubes. The best method of selecting tubes in pairs is to overlap the G1/Ia curves, the superimposed curves show us that the tubes have the same plate current and the same transconductance in the whole operating range. One point matching method used with analog tube testers is a pretty good compromise solution, but identical tubes at one point can have big differences at higher or lower currents, testing in 20÷50 points with these devices and drawing curves take hours for each tube. Roetest does this quickly and with great precision. This is the best way to select pairs, based on overlapping curves. The tubes meet datasheet specifications, first the quality tests – filament test, shorts test, gassy test (Ig1, vacuum factor, Ia variation with 1M2 grid series resistor), kathode isolation (leakage to filament), then quantity tests – value of current for plate, G2, kathod, G1, value for transconductance, gain, G1 curve, Ia curve etc., all results for these tests can be seen on te datasheet delivered for each tube. Those who use tubes are more familiar with terms like bias, gain (µ), plate current, slope/transconductance, and maybe someone is wondering what the term „D of plate” in the measured data means. Its value in itself is not so important but it is useful to calculate the other parameters taking into account Barkhausen's tubular formula S x D x Ri = 1 (slope * penetration * internal resistance=1), where D is –dUg/dUa at Ia=const. Barkhausen vas a german physicist, he was “the guru” of tubes, his theory and formulas guided the entire period of electronic tubes.