I have been using an old Bryston 4b (the original version) for many years. Have now been offered Bryston 4b Pro at a reasonable price. Could someone tell me the difference in age and quality between the two amps. Specifically, did the 4b Pro come after the 4b and before the 4b ST and SST, and is it substantially better than the original 4b. Also I am terribly confused about the evolution of the various 4b versions. Is it possible to get a brief history of these highly rated amps and the changes made with each new version?
