This is true Soren….I received this from Frede some time ago:
It is actually a ”short list” 😊
BC 550B for npn
BC560B for pnp
When the Beolab was designed (before 1967) only a few transistors were available is really low noise versions – therefore B&O have chosen a number of different types of coarse also being able to be used and meeting the actual voltage level. But I have for many years used the above type in the pre-amplifiers.
And I am using the transistors type B because higher gain in classic electronics design is not a good idea (this is my opinion 😊)
B U T — for the power amplifier and the power supply – I only use the original RCA types !!!
For the output power transistors and psu transistors — I am only using the original Motorola or RCA (there are to many “fake” 2N3055 out there).
When I am writing the original it is actually the original because I re-use these transistors from Beolab 5000 which is scrapped.