Nelson Pass has offered a great deal to the world of high end audio amplification, and one of the things I like best about him is he encourages DIY projects of his designs. This tells me he cares about the music deeply, above profit motives. Here in one of his prolific and open discussions he goes into cascode amplifier design (https://www.passdiy.com/project/amplifiers/cascode-amplifier-design).
He’s always been outspoken in regard to the degradation of audio quality in favour of low THD specifications (The THD wars. Why lower distortion often doesn’t equal better sound quality). But how does one solve the dilemma? Class A amplification is the obvious answer, and one which many amps of the day went to, but Class A amplification is grossly inefficient at best, and completely unreliable at worst (The good, the bad, and the toasty about Class A amplification).
He subsequently went on to introduce STASIS, which uses optical bias current and MOSFETs, innovations that are present in his Threshold Amps and the Nakamichi PA7, which is firmly based upon Nelson Pass engineering precepts (The Nakamichi PA-7 power amplifier).