Hello and welcome aboard!
This is normal and exactly so was with my 4B SST and now with a pair of 7B SST2.
Well this is not really kind of equipment you would like to turn on and off frequently.
Regardless of what others mght think my opinion is that these amps perform their best after working for a few hours.
Keeping them warm helps users get best results immediately.
Many don´t turn them off at all!
P.S. Doesn´t this buzz give you some feeling like turning on something powerful and important like powerplant or something alike?
Wow, love my Brystons!
Yesterday evening my dealer received his 14B SST2 19´version with handles in silver. This one looks mighty as it sounds, awesome!!!