Elrog 300B vs Takatsuki 300B tubes

I got a pair of ER300B from TrueAudiophile in March 2015. One of tubes has failed in June 2015. As per TrueAudiophile request I shipped tubes directly to the factory.
Here is from the email from TrueAudiophile regarding conversation with the factory:
... I went over it very calmly with him explaining he needs to honor the warranty. He refused. He then hung up on me....
I also email to Elrog stating tubes S/N, date of purches etc. No reply.

Mathias,
I emailed Elrog multiple times regarding my tubes, got no reply.
Here it is again:
Serial numbers: 09471 and 09505.
Tubes have arrived to Elrog on 20.06.2015 11:00

Tubes were used in AN amplifier, cathode bias 900 Ohm,
HT 425V, 5.0v DC regulated heaters PS.

Tube failed during listening, there is no issue with the emission or heater, tube just turned into diode.

You respond is appreciated.

Hi Cyrus,
I'm not in a position to recommend anything regarding AN or Elrog.
The best whould be to address your question to Elrog engineers.
The only thing I'm comfortable to say that in my setup and with my music preferences I like very much what Elrog300Bs do.
Thank !

Wyan001:
Unfortunately you can't make adapter to add R to cathode bias: heater pins should be connected directly to 5v heater supply and virtual center of the heater goes via bias resistor to the ground (that's where additional R supposed to go). Also cathode resistor (in this case exiting one in series with the 200 ohm) is bypassed by capacitor.

I also got my replacement pair (Matthias, thank you very much) and they sounds like ... Elrogs!