It is been a while since I listen to this Bottlehead Crack Headphones amplifier.
You can follow this link when I received it at the first time here, then the cleaning process here, and when I replaced all the vacuum tube with the new old stock Tungsol 5998 and GE 5814 here.
This Bottlehead Crack amplifier is a very simple circuit with the output transformer-less design. I can say that I become a solid-state guy for a long time because building a vacuum tube amplifier is expensive for the vacuum tube itself. Then the good transformers is even more expensive to buy. But that is not the case with this Bottlehead Crack amplifier.
If you want to listen the music with better sound quality and definitely want your headphones to have a good amplifier to pair with, then you should consider to have this Bottlehead Crack amplifier.