Where can I find suitable tubes for DIY single-ended power amplifiers and 300B SET projects?

For DIY single-ended power amplifiers and classic SET projects, high-quality directly heated triodes are especially sought after, for example 300B, 2A3, PX4, PX25, 45 and AD1. Such types are the heart of many self-build concepts, whether classic 300B SE, 2A3 monos or more elaborate projects with PX4, PX25 or AD1. At BTB, suitable tubes from Linlai, KR-Audio (Kron), Emission Labs and PSVANE are available for this. EML currently explicitly lists these families in its range, including 320B XLS (AV32BSL), 520B XLS as a replacement for AA52bsl, 300B Mesh or 300B XLS (AA300B), 2A3 Mesh and 45 Mesh. PSVANE offers, among others, 300B and 2A3, and KR continues to position itself as a manufacturer of high-quality audio tubes.