There are a multitude of different design philosophies, each seemingly providing the silver bullet to fidelity. Nelson Pass has his own philosophy and mentions a list of amp fads and design issues in his owner's manual for my Aleph 3. The link is www.passlabs.com/pdf/aleph/a3man.pdf. Look under the "Product Philosophy and Design Theory" section. Here's an excerpt:
"We have heard Triodes, Pentodes, Bipolar, VFET, Mosfet, IGBT, Hybrids, THD distortion, IM distortion, TIM distortion, phase distortion, quantization, feedback, nested feedback, no feedback, feed forward, Stasis, harmonic time alignment, high slew, Class AB, Class A, Pure Class A, Class AA, Class A/AB, Class D, Class H, Constant bias, dynamic bias, optical bias, Real Life Bias, Sustained Plateau Bias, big supplies, smart supplies, regulated supplies, separate supplies, switching supplies, dynamic headroom, high current, balanced inputs and balance outputs...Leaving aside the examples of marketing hype, we have a large number of of attempts to improve the sound of amplifiers, each attempting to address a hypothesized flaw in the performance."
A number of these is addressed in his subsequent comments as he describes his design rationale for the Aleph 3.
"We have heard Triodes, Pentodes, Bipolar, VFET, Mosfet, IGBT, Hybrids, THD distortion, IM distortion, TIM distortion, phase distortion, quantization, feedback, nested feedback, no feedback, feed forward, Stasis, harmonic time alignment, high slew, Class AB, Class A, Pure Class A, Class AA, Class A/AB, Class D, Class H, Constant bias, dynamic bias, optical bias, Real Life Bias, Sustained Plateau Bias, big supplies, smart supplies, regulated supplies, separate supplies, switching supplies, dynamic headroom, high current, balanced inputs and balance outputs...Leaving aside the examples of marketing hype, we have a large number of of attempts to improve the sound of amplifiers, each attempting to address a hypothesized flaw in the performance."
A number of these is addressed in his subsequent comments as he describes his design rationale for the Aleph 3.