Matthias also brings to the table an interesting observation about the current draw of 1.5 amps for the EML 300b XLS. It is 25% higher than a standard 300b which is 1.2amps. This is something I have mentioned in these pages to folks who were considering buying the EML's since they are considered drop in replacements for standard 300b's. I have over spec filament transformers in my amp that can handle the extra current so it is no problem but the bigger concern is that 25% extra current draw reduces the voltage accordingly. I noticed this when I first installed my new EML's. No problem since I can simply add or subtract the dropping resistors in my filament supply and I check my voltages regularly since I am a DIY person. This is not so easy for a person who is not.
All this to say that when considering different types of non standard 300b tubes it is very important to do the research to make sure your amplifier can handle this tube properly -Jet
All this to say that when considering different types of non standard 300b tubes it is very important to do the research to make sure your amplifier can handle this tube properly -Jet