@bestestube = best tubes, best testing, best matching - a very pretentious selection of the best tubes from large batches, only few tubes from any batch meet our requirements for this selection.

         You are looking to a matched pair 6N3P tube, all with same date III.1981, 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 are matched in the whole operating range, not only in one point. Usually from a batch of 100 double tubes, about 50 are unmatchable because differences between the 2 triodes in the same tube are over 10%, and from the rest of 50 could be obtained about 10 pairs +/- 2.5% and about 10 pairs +/- 5%. In this listing are only the best 35 pairs, +/-2.5%, from original 4 boxes of 100 tubes same date, less than 2.5% is almost impossible at double tubes.

           The tubes (batch of 400 pcs.) are tested in our very well equipped laboratory, specialized in tube testing, with very well qualified personnel and with long experience for this. Before measuring each tube was heated for 30 minutes, for best results and for revealing gassy tubes.
       You will get the best tubes selected and the best sorting in pairs that is possible. If you have a sophisticated amp/preamp with 1% tolerance components and high quality output transformer, don’t buy tubes at random with +/- 30% tolerance (means possible differences of 60% between tubes). As we can see in original datasheet for 6N3P, value for plate current is 6-8.75-11.5 mA, this means 68%-100%-131%; in fact these values are for cathode bias 240 ohmi which realize local d.c. feedback that narrows the spread, with fix bias is larger. These large spread of parameters could be found at many kind of new tubes and from any producer, even some of them don’t say explicit in their datasheets.

         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.

The buyer will receive a pair = 2 tubes safe packaged in a box, we don't use envelopes or bags.

We send as priority mail, with tracking number, usually next day after payment. Shipping time depends only by post services, if you don't  have enough patient please don't buy.