Like Peanut Butter and Chocolate — Nelson Pass / 2002

Pass Labs XA Series Power Amplifiers For over ten years, the Aleph series of single-ended Class A amplifi ers have received praise for their outstanding sonic defi nition, warmth, and smoothness; and have often been compared favorably with the very best tube amplifi ers. The Aleph topology achieves state-of-the-art performance with a very simple linear design, and is additionally one of the most stable and reliable audio amplifi ers in existence. A considerable number of audiophiles have found themselves bi-amping their loudspeakers, putting Pass X amplifi ers on the bottom for power and control, conjoined with Alephs on the top… More...

Super-Symmetric Amplification — Nelson Pass / 1998

U.S. Patent # 5376899 describes a new amplifying circuit topology that takes advantage of the character of special matched balanced amplifiers that are cross-coupled to provide cancellation of distortion and noise. The result provides high performance with very simple linear circuits, better than previous efforts by an order of magnitude. We have dubbed the approach Super-Symmetry (Su-Sy), an homage to particle physics. Super-Symmetry works by exploiting the complementary characteristics of precision matched balanced circuits to differentially reject distortion and noise, and extends this symmetry to make the distortion and noise virtually identical on each half of a balanced amplifying circuit.… More...