Diamond matched quad 6P3S-E NOS = 4 identical tubes with superimposed curves, identical plate current and transconductance.Never used tubes, in original boxes 50 pieces same date, look impeccable, no spots or sign of oxide. Military OTK rhombus is stamped on each tube.
This selection was made only with identical tubes from a large batch, plate current in range tight around 100%, weaker tubes (under 95%) from this batch are listed separately, cheaper.
Tubes were burned for about 1/2 hour, made all quality tests, measured parameters and traced curves, then selected in quads tubes with superimposed curves, this means same plate current and transconductance for entire working range. Conditions for test - exact the ones mentioned in original datasheet: 250V plate, 250V screen, -14V grid, 6.3V heater.
In the pics can be seen curves and full test protocol for each tube of a quad, all quads have good specs and perfect matching.
Many available, send message if you need more quads or octet.
Usually output tubes are selected by honest factories / sellers in a range of max. 5% and they work fine and are cheaper, we made this selection for who wants perfect matched 0% tubes for a perfect sound, using the best existing tube tester, it's calibration being checked weekly.
Substitution / equivalency: A big advantage of 6P3S-E is the gold plated grid, this means that secondary emission won't appear after the tube become very hot accidentally or even in normal use high biased in high ambient temperature / low ventilation.
6P3S-E tube is a higher quality version of russian 6P3S, from our experience testing few thousands of 6P3S (version without -E) many are gassy, part of them can be recovered with some burn out but a fuse can be burned in this process or more damages.
6P3S-E is perfect equivalent and direct replacement for any version of 6L6 and 5881.
Also 6P3S-E can be used as replacement of EL34 and some KT's. Usually we listen music in the workshop from an EL34 amp but output tubes changed with 6P3S-E, max. power is lower but we feel a warmer sound. Don't do such replacements if you don't understand a schematic, biasing principles and to read / understand a datasheet.
Do not make confusion between 6P3S-E = 6L6 and another russian tube 6P6S = 6V6.
Price is for one quad = 4 tubes matched as described, in original boxes, + one original datasheet, + printed test protocol for each tube.
Tested with professional tube testing system Roetest V10, the best actually existing tube tester.
We ship 1-3 days after payment, usually next day, very safe packaged, priority airmail with tracking number.
Shipping time is around 10 days to Europe and 14 days worldwide.
Outside EU, depending on the case / destination, custom services may add delays.