The Inner Ear Report - Wyetech Labs Sapphire 300B

Unlike most 300B-based amplifiers, however, bass finished with authority and muscle, rounding up harmonics not heard with other amplifiers. As expected, the highs were nothing short of fascinating: smooth, harmonious, lush and exquisitely textured. 

…the Sapphire amps asserted their presence with a liquidly smooth, full-range sound that can be described as seductive.