For my Portal Panache Integrated (designed by Nelson Pass), they recommended that for best sonics it be left on 24/7 (there was no standby switch)...for my high power Pass Class A mono blocks, Pass says there is no short or long term harm in leaving them on 24/7, simply my decision based on listening habits, sonics, electric usage...sure seems manufacturers of seemingly similar products have various recommendations...
Amp — Leave on or turn off
I always turned my Benchmark AHB2 amp off after use every night. After all, why is there an on off switch on the front panel if not to do that? Last night I accidentally left it on. This morning, when I played my first record, I couldn’t believe my ears. The same record I played last night sounded infinitely better. I tried a second record and that, too, was much better.
I know there’s a debate on the question of leaving an amp on all the time.
I now know where I stand!