ecc83 mullard tube 12ax7 philips pair valves

red pip top NAT LAB laboratory science department Made in Holland Ultra rare

2 TUBES = 2  VALVES = 2 VINTAGE VACUUM TUBES = 2 röhren = two pieces

Red tipped laboratory selected
15mm Long Plate
Dark grey plate ribbed welded
O getter halo
plate with Silver tongues on rounded corners
high quality tubes for preamplifier preamp per input phono driver stage first stage audio

ECC83 Double Triode  Audio Frequency High Gain
ECC83 = 12AX7 = B339 = 95-127-01 = 6L13 = CM1 = ECC83S
Similar Tubes  Normally replaceable-slightly different:   0AX7 ; 12AX7A ; CV492 ; E2164
Other class quality (otherwise equal):   7025 ; CV4004 ; E83CC ; M8137
Other characteristic (electr. data):   12AY7 ; 6N4_China
Other base and other heater:   6EU7 ; ECC808
Multiple differences or of other kind:   5751 ; 7729
Successor Tubes 1963   ECC808   5751WA
Base Noval B9A
Filament Heater Vf 12.6 Volts / If 0.15 Ampere / Indirect / Parallel / series AC/DC

fully tested on calibrated tube tester tv7d/u 
Test results as follow: 60/60 ; 50/50
code I63 DELTA △ red tip  selected (reference good at 32/32 ) on tube tester calibrated TV7D/U one with  geloso round logo on glass 

All 2 tubes own red tip , selected nat laboratory , selected for pre amplifier stage audio 

box 154
pair 2