Where can I find suitable replacement tubes for boutique guitar amps and smaller amp brands?

For boutique amps and small-series amps, careful tube selection is especially worthwhile, because many of these amplifiers react strongly to response, dynamics and the fine-tuning of the preamp stage. This applies, for example, to Koch models such as Twintone, Powertone or The Greg, to Diezel classics such as VH4, Herbert, Hagen or Einstein, to Bugera series such as 1960, 333, 6262 or Trirec, as well as to Madamp kits and similar concepts. Typical tubes in this field are mainly EL34, 12AX7 / ECC83 and 6L6GC. In many of these amps, high-quality S4GB tubes are particularly interesting when stable, lower-noise and tonally balanced performance is required. Many suitable types for these amplifiers are also available from BTB in selected quality and, on request, as premium-matched power tubes.