There are all kinds of transistors. In the 80's the Motorola Transistor databook was the thickest databook on the shelf. It was a good 3 inches thick. It was thicker than the TI 54/74 CMOS/LS/HC series databook on discrete logic.
I would expect that the Bryston Engineering team would choose the best transistor, based on the type of transistor properties they need, for that part of the circuit that they're designing.
Current Gain parameters, Output Capacitance and Total Power dissipation are all factors for the output stage for initial consideration. How they perform, in the circuit, on the test bench is probably the deciding factor if they have several different transistors they're considering.
For input stages, they would need something based on a different set of parameters.
In any case, the transistor is a single item in a circuit with many other components (caps, inductors, resistors, diodes and possibly even integrated circuits) that provides the audio signal that you eventually hear.
The circuits and the components and how they're laid out are essentially Bryston's IP. I appreciate how open Bryston has been about how they design their products.
HsvHeelFan
