6P14P-ER is the best variant between all 6p14 and EL84 tubes, a classification of qualities in ascending order would be 6p14p, 6p14p-k, 6p14p-v, 6p14p-ev, 6p14p-er, ER variant being high reliability, long life an tight specs tube, NOS -from the times when there was no saving for rare metals and precious metals, especially for military use tubes. Each tube contains few mg of pure 24K gold for g1.

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.

In addition to the tubes, you will receive an individual data sheet, one A4 page for each tube.The tubes (batch of 200 pcs. same data in original individual boxes and 50 pcs boxes) are tested in a very well equipped laboratory, specialized in tube testing, with very well qualified personnel and with long experience for this. All tube data can be seen in the printing protocol, all tubes meet the manufacturer's datasheet specifications. Before measuring each tube was heated in a separate support for 30 minutes, a shorter heating leads to erroneous results and does not indicate gassy tubes.

6P14P is equivalent to many tubes, all can be seen at the bottom of the printed page (CV8069 etc.).

Condition for test: Up=250V, Uscreen=250V, Ug1=-7.3V. For this sorting we accepted only tubes with 2 digits nanoA for Ig1, this means a very good vacuum inside (under 1% Ip modification with 1M2 resistor g1 series), the most important thing that must be tested for NOS tubes.

You will get the best tubes selected and the best sorting in pairs that is possible. If you have a sophisticated amp with 1% tolerance components and high quality output transformer, don’t buy tubes at random with +/- 40% tolerance (means possible differences of 80% between tubes). These 80% could be found at new tubes 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.