How would a Neve single ended class A microphone preamplifier sound with a BD139 instead of 2N3055

At your risk.


See nearby posts for the great sound of a BD139 bipolar transistor driving a fullrange speaker. This is the Pleiades BD139 one transistor power amplifier in class A (electrons flowing all the time). For example:
https://euroelectron.blogspot.com/2019/06/winding-toroidal-output-transformer-for.html


Compared to 2N3055 the BD139 gives excellent high frequency sound with no feedback. Much easier to make an output transformer as collector current can be of the order of 50mA.