Phase -Coherent Crossover Networks — Nelson Pass / 1982

The importance of phase response in the audio chain has been brought to greater focus recently by equipment claims of phase coherency, (the output signal has the same phase relationships as the input signal). It is not particularly obvious that two different frequency components of a signal can go into a device at precisely the same time and emerge at different times, but it is extremely common. All audio components distort the phase of the signal to some degree-even air alters the time alignment of a signal, but the biggest offenders are loudspeakers and their crossover networks. Phase shifts in… More...

Zen Variations 4 — Nelson Pass / 2002

The Penultimate Zen is the sum of several incremental improvements to the original Zen amplifier of 1994. Eight years just flies by, doesn’t it? These improvements are contained in parts 2 through 4 of the Zen Variations, and is likely the last version of this amp, although by no means the end of the variations on the theme of single stage amplification. In part 2 we developed an improved active current source load for the single gain device which is at the heart of the amplifier. Originally designed for the Aleph amplifier series, this current source doubles the output current… More...