ecc808 6kx8 Siemens Germany tube preamp tubes quad valve same code c60 D5F1

4 tubes = four vintage vacuum tubes Siemens ECC808 = 6KX8

Tested on tube tester Funke W19 

reference good at 1,8mA &  1,8mA 

test tube 1 = 3mA & 2,5mA   code c60 D5F1 
test tube 2 = 3,1mA & 1,9mA  code c60 D5F1
test tube 3 = 2,6mA & 2,6mA  code c60 D5F1
test tube 4 = 2,8mA & 2,2mA  code c60 D5F1

all 4 tubes with same code , same inner structure, same O getter 
with red tip selected 
same old stock production 

ECC808 = 6KX8
dual triode 

The ECC808 is a low hum, low microphony and low crosstalk dual triode for high sensitivity AF amplifiers, especially for two channel stereo circuits. The static values of the ECC808 are practically identical to those of the ECC83. Unlike the ECC83, however, the ECC808 is only intended for parallel heating (6.3 V / 0.34 A).
In combination with a more practical socket circuit by improved shielding and better cathode isolation, a particularly high freedom from hum could be achieved. (Ripple voltage at G1 approx. 4 μV with pin 4 at ground.) The microphony resistance could also be improved by a factor of 3.
Due to the good shielding between the two systems, loudness and clarity controls can also be arranged between the two stages without difficulty in the case of cascade amplification. With two-channel amplification, a crosstalk attenuation of -50 dB at 10 kHz can be achieved.

box 152