Zen Amplifier Revisited — Nelson Pass / 1994

I must say that I have been very gratified by the response to the Zen amplifier from the last issue of TM. Since writing the article I have had an opportunity?to build another 25 copies of the amplifier, listen to it on a larger variety of loudspeakers, absorb criticism from the readership, and generally meditate on the project. Areas of criticism of the design all relate to the objective, measurable performance, but in addressing them, I found that the subjective performance improved with the measurements. All of the changes are performed without altering the original topology of the project amplifier.… More...

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...