Elrog 300B vs Takatsuki 300B tubes

May it be that the filaments of the Elrogs are very bright after switching on the amp for 2 or 3 seconds and then the brightnes is decreasing within the next about 5 to 10 seconds?

Brightness on turnon that slowly dies down is a sign of overvoltage on turnon and will quickly harm the filament.  This behavior happens in a number of 300B amps and the thoriated filaments light up much quicker making the behavior much easier to notice.

dave

Well, that bodes well for the end results of Charles' cathode resistor modification experiment, which was explicitly suggested to decrease a surge in voltage at power-up.  Hopefully that does indeed fix Elrog reliability problem... I guess we'll know in 6 months.

What I am referring to is the filament voltage at turnon and this has little to do with the value of the cathode resistor.  If the filament glows brighter at first and then settles down to "normal" it is being unduly stressed on turnon.  This goes for all directly heated tubes and it just so happens that the thoriated tubes make the situation much more visible due to their quick turnon.

dave

Charles, I did get your email and responded.  Did you not receive it?  Things are going reasonably well here, but I am doing everything I can to get lost in the hills.  Yesterday's hike was 14.4 miles with 3700 ft elevation gain.  Four hikes altogether in the last week. Paradise.   Not getting much listening time in.  2-3 hours a week at best.  I've been following the fuse discussion, and want to hear your thoughts on black vs red, especially in the CSL.  I still have a stock fuse in mine, so this could be a big step forward.  Keep me posted and let me know if I need to resend the PM.