Jürgen from NixieKits.eu is working on a new design for a line level preamplifier. This new device will have the same footprint as his headphone amp and he has been kind enough to share the schematics so far. The cool part of this design is that will support a range of tube with both 6v and 12v filaments. For example the ECC81 / 82 / 83 (12Ax7) have a 12V filament. All "newer" tubes, e.g. ECC88 / E802CC... and all Russian types (6N1P...) have a 6V filament.