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...

Bride of Zen — Nelson Pass / 1994

This is the second installment of a trilogy of construction projects centered around the performance obtainable from absolutely minimalist circuitry. Part one described the Zen amplifier, a 10 watt single-ended class A power amplifier using a single MOSFET gain stage. In this piece we will examine its preamplifying mate, also a single gain stage MOSFET circuit. A lot of what I might say about this design has already been expressed in the Zen amplifier piece, and will not be repeated here. It is enough to say that I continue to be very intrigued by the sound of very simple topologies,… More...