All,
thanks a lot for the positive responses and good wishes. As mentioned in my post so far there was a single beta tester who used the tubes in a Frankenstein amp. He had them for almost half a year now. I wanted to have this test first before releasing the tubes for the Frankenstein. Since this release only happened now, there are no additional users of Frank amps yet who have the new Elrog tubes.
@jetrexpo: The choice of operating point depends more on the amp design than on the tube. As long as all max limits are not exceeded any op point which is preferred by the amp designer is ok. 450V/90mA would already be slightly over the limit and thus is not recommended. I personally use fairly traditional op points of about 350V/65-75mA
@brownsfan: The inrush current issue was solely relevant for the filament supplies. When the tube filaments are cold they are basically a short. If the filament supply uses brute force voltage regulation it will push a lot of initial current into them. An external softstart will probably not do much there. We also saw that some current regulated filament supply kits for DIY amps actually start with a current spike and initially put 7V across the filaments before settling to 5V. This is not healthy for any 300B, but it simply killed the early Elrog 300Bs. Also a tube rectified B+ supply doe snot have any affect on slowing the filament inrush current. But as mentioned the tubes are more robust now to be able to withstand some abuse at turn on. Yet a well designed amp with good filament supply and conservative op points will ensure a longer tube life. Not only for Elrog 300Bs but for any brand.
Best regards
Thomas
thanks a lot for the positive responses and good wishes. As mentioned in my post so far there was a single beta tester who used the tubes in a Frankenstein amp. He had them for almost half a year now. I wanted to have this test first before releasing the tubes for the Frankenstein. Since this release only happened now, there are no additional users of Frank amps yet who have the new Elrog tubes.
@jetrexpo: The choice of operating point depends more on the amp design than on the tube. As long as all max limits are not exceeded any op point which is preferred by the amp designer is ok. 450V/90mA would already be slightly over the limit and thus is not recommended. I personally use fairly traditional op points of about 350V/65-75mA
@brownsfan: The inrush current issue was solely relevant for the filament supplies. When the tube filaments are cold they are basically a short. If the filament supply uses brute force voltage regulation it will push a lot of initial current into them. An external softstart will probably not do much there. We also saw that some current regulated filament supply kits for DIY amps actually start with a current spike and initially put 7V across the filaments before settling to 5V. This is not healthy for any 300B, but it simply killed the early Elrog 300Bs. Also a tube rectified B+ supply doe snot have any affect on slowing the filament inrush current. But as mentioned the tubes are more robust now to be able to withstand some abuse at turn on. Yet a well designed amp with good filament supply and conservative op points will ensure a longer tube life. Not only for Elrog 300Bs but for any brand.
Best regards
Thomas