Subscribed,considering one of his Class A power amps.
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I have owned a few Pass designs - they come in so many different varieties, but amplifiers are his forte. Here are some of my favorites.
Threshold S/550e amplifier: What a beautiful, heavyweight classic. Maybe the original behemoth amplifier. Output transistors galore and 2 sizeable toroid transformers. Strangely, bass was not a strong point. This thing weighed 97lbs, but what a PITA to move.
Adcom 5800: Another original design. 3 gain stages and 2 power supplies: one for the front end, the other for outputs and heat sinks with an active cooling system. Very nice sounding. Bass was a strong point here. Too bad Adcom went bust.
Aleph 2 mono blocks: Very innovative 2 gain stage, single-ended Class A MOSFET design with a patented output stage - a very simple circuit. Beautiful sound, but not the absolute last word in transparency or bass. Ran not quite hot enough, ~ 125 degrees, to fry eggs.
XVR-1 Electronic Crossover: Discrete Class A, low-noise design implemented with a dizzying, 2 sided circuit board layout, and adjustable crossover settings offering 4 filter slopes, 39 frequencies choices, and over 20 MILLION possible settings according to the manual.
I also owned 2 Pass Labs preamps an X0.2 and an XP-20 but they are Wayne Colburn designs.
No one in audio history has the long track record of so many original designs as Nelson Pass. He's also unique in sharing intellectual property, circuit designs, so that others may learn.
I bought what was then a pretty revolutionary amp. the Threshold s500. The first professionally made really high current amp. 1980?
When I replaced it 20 years later with a Pass x350… I was shocked at the difference. More current, solidity, midrange, a huge advance.
The XA series, has been incredible as well. I have not owned one, but would have liked to. Pass stuff just gets better over time.