M8137/ECC83/12AX7 MULLARD GREY PLATE O GETTER TESTED WITH ROETEST V10 NOS
Tubes NOS/NIB, never used, Tubes and boxes look impeccable.
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.
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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.
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