Nelson Pass (born June 27, 1951) is an American designer of

audio amplifier An audio power amplifier (or power amp) electronic amplifier, amplifies low-power electronic audio signals, such as the signal from a radio receiver or an electric guitar pickup (music technology), pickup, to a level that is high enough for dr ...

s. Pass holds at least seven U.S. patents related to audio circuits.

Career

Studies, PMA and ESS

In 1974, he received his BS in physics from the University of California-Davis.http://www.diyaudio.com/forums/showthread.php?postid=1600879#post1600879 NP@diyaudio During his studies, he and Mike Maher founded the small speaker company PMA.http://stereophile.com/interviews/1191pass/ Interview with NP From 1973 to 1974, he was employed at ESS and assisted Dr. Oskar Heil with crossover design, woofer selection, and final build cabinetry of audiophile, consumer grade loudspeakers. Nelson Pass holds 6 patents related to magneplanar speakers.

Threshold

After graduating in 1974, he and René Besne founded high-end amplifier company Threshold Electronics on December 5, 1974. Later, Joe Sammut became the third partner. Threshold is perhaps best known for the "Stasis" amplifiers (a design later also produced under license by

Nakamichi was a Japanese consumer electronics brand founded in Japan which gained a name from the 1970s onwards for audio cassette decks. Nakamichi is now a subsidiary of Chinese holding company Nimble Holdings. Nakamichi manufactured electronic devic ...

). During his time there he demonstrated an Ion Cloud loudspeaker at CES in 1980, based on ion wind technology. He sold Threshold Electronics in 1997. The company continued without Nelson Pass under the name Threshold Audio.

Adcom

In the mid 1980s, Pass designed the well-reviewed Adcom GFA-555 amplifier. This was a Bipolar Junction Transistor (BJT) based design.http://www.stereophile.com/solidpoweramps/678/index.html Stereophile review of GFA-555http://www.audiokarma.org/forums/showthread.php?t=74228 Discussion of Nelson Pass work at Adcom Nelson also designed the GFA-5XXX MOSFET-based series of high-bias class-AB amplifiers for Adcom (i.e. -5300, -5400, -5500, -5800).

Pass Labs

Pass founded

Pass Labs Pass Labs is a high-end audio company based in Auburn, California, United States founded by Nelson Pass in 1991. Pass Labs makes amplifiers, preamplifier and speakers. History Nelson Pass founded Pass Labs in 1991 and was based in Foresthill, ...

in 1991. Pass (and his companies) designed and produced the Class A "Aleph" series of single-ended amplifiers. Pass Labs produces the X series amplifiers, which make use of the "

supersymmetry Supersymmetry is a Theory, theoretical framework in physics that suggests the existence of a symmetry between Particle physics, particles with integer Spin (physics), spin (''bosons'') and particles with half-integer spin (''fermions''). It propo ...

" topology patented by Pass, to give extremely low distortion levels, and more recently the XA series of amplifiers, which advantageously combines aspects of the Aleph design with the "supersymmetry" technique. Recently, Pass Labs has introduced a loudspeaker, and Pass DIY has increasingly explored the field of high-efficiency and full-range speakers as a complement to minimalist amplifier designs.

First Watt

In parallel with

, Pass also runs First Watt, a self-described "kitchen table" commercial venture where Pass hand-builds (in very limited numbers) some low-power / minimalist designs he chooses to not series produce through Pass Labs. His SIT amplifiers are the first of a new generation of audio amplifiers using Static Induction Transistors in a single-stage, single-ended, Class A circuit without feedback or degeneration. The SIT chip combines a square-law input character with a low impedance output to form the only solid-state gain device, which Pass claims, "behaves like a triode tube." There is no output transformer on the SIT amps. The point of the SIT is that it behaves like a triode but at lower voltages and higher currents, so it doesn't need a matching transformer to deliver power to 8 Ohms. Like tubes, SITs have soft overload clipping. When brief bursts of musical energy occur, SITs react with rounded waveform tops instead of sharp and hard clipping of solid-state. SITs have a curve which looks a lot like a triode vacuum tube; low at first and climbs steadily. The distortion curve is similar, a steady rise instead of a valley with high distortion at both ends.

DIY

Pass has been supportive of the

DIY audio DIY Audio, do it yourself audio. Rather than buying a piece of possibly expensive audio equipment, such as a high-end audio amplifier or speaker, the person practicing DIY Audio will make it themselves. Alternatively, a DIYer may take an existing ...

community by way of published articles (notably in ''The Audio Amateur'') as well as providing schematics for out-of-production models on the Pass Labs site, and more recently for the First Watt site. He often interacts directly (and somewhat tersely) with audio hobbyists.The DIY Audio site
/ref> His nickname among the DIY audio community is "Papa".

References

{{DEFAULTSORT:Pass, Nelson American audio engineers American technology writers Living people 1951 births University of California, Davis alumni