Nelson Pass

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Nelson Pass (born June 27, 1951) is a designer of audio amplifiers. [1] Pass holds at least seven U.S. patents related to audio circuits. [2]

Contents

Career

Studies, PMA and ESS

In 1974, he received his BS in physics from the University of California-Davis. [3] During his studies, he and Mike Maher founded the small speaker company PMA. [4] 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. [3] Nelson Pass holds 6 patents related to magneplanar speakers. [5]

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. [4] Threshold is perhaps best known for the "Stasis" amplifiers (a design later also produced under license by Nakamichi). During his time there he demonstrated an Ion Cloud loudspeaker at CES in 1980, based on ion wind technology.[ citation needed ] 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. [6] [7] Nelson also designed the GFA-5XXX MOSFET-based series of high-bias class-AB amplifiers for Adcom (i.e. -5300, -5400, -5500, -5800). [8] [9]

Pass Labs

Pass founded Pass Labs 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, [10] which make use of the "supersymmetry" 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,[ when? ] 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 Labs, 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. [11] [12] 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. [12] 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. [13]

DIY

Pass has been supportive of the DIY audio 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. [14] [15] [16] His nickname among the DIY audio community is "Papa".


Related Research Articles

<span class="mw-page-title-main">Audio power amplifier</span> Audio amplifier with power output sufficient to drive a loudspeaker

An audio power amplifier amplifies low-power electronic audio signals, such as the signal from a radio receiver or an electric guitar pickup, to a level that is high enough for driving loudspeakers or headphones. Audio power amplifiers are found in all manner of sound systems including sound reinforcement, public address, home audio systems and musical instrument amplifiers like guitar amplifiers. It is the final electronic stage in a typical audio playback chain before the signal is sent to the loudspeakers.

<span class="mw-page-title-main">Damping factor</span> Ratio of impedance of a loudspeaker

In an audio system, the damping factor is defined as the ratio of the rated impedance of the loudspeaker to the source impedance of the power amplifier. It was originally proposed in 1941. Only the magnitude of the loudspeaker impedance is used, and the power amplifier output impedance is assumed to be totally resistive.

<span class="mw-page-title-main">Horn loudspeaker</span> Loudspeaker using an acoustic horn

A horn loudspeaker is a loudspeaker or loudspeaker element which uses an acoustic horn to increase the overall efficiency of the driving element(s). A common form (right) consists of a compression driver which produces sound waves with a small metal diaphragm vibrated by an electromagnet, attached to a horn, a flaring duct to conduct the sound waves to the open air. Another type is a woofer driver mounted in a loudspeaker enclosure which is divided by internal partitions to form a zigzag flaring duct which functions as a horn; this type is called a folded horn speaker. The horn serves to improve the coupling efficiency between the speaker driver and the air. The horn can be thought of as an "acoustic transformer" that provides impedance matching between the relatively dense diaphragm material and the less-dense air. The result is greater acoustic output power from a given driver.

The Williamson amplifier is a four-stage, push-pull, Class A triode-output valve audio power amplifier designed by D. T. N. Williamson during World War II. The original circuit, published in 1947 and addressed to the worldwide do it yourself community, set the standard of high fidelity sound reproduction and served as a benchmark or reference amplifier design throughout the 1950s. The original circuit was copied by hundreds of thousands amateurs worldwide. It was an absolute favourite on the DIY scene of the 1950s, and in the beginning of the decade also dominated British and North American markets for factory-assembled amplifiers.

Klipsch Audio Technologies is an American loudspeaker company based in Indianapolis, Indiana. Founded in Hope, Arkansas, in 1946 as 'Klipsch and Associates' by Paul W. Klipsch, the company produces loudspeaker drivers and enclosures, as well as complete loudspeakers for high-end, high-fidelity sound systems, public address applications, and personal computers.

PS Audio is an American company specializing in high-fidelity audio components equipment for audiophiles and the sound recording industry. It currently produces audio amplifiers, preamplifiers, power related products, digital-to-analog converters, streaming audio, music management software and cables.

<span class="mw-page-title-main">Pass Labs</span> American audio company

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.

Dynaco was an American hi-fi audio system manufacturer popular in the 1960s and 1970s for its wide range of affordable, yet high quality audio components. Founded by David Hafler and Ed Laurent in Philadelphia, Pennsylvania in 1955, it's best known product was the ST-70 tube stereo amplifier. They also manufactured other tube and solid state amplifiers, preamplifiers, radio tuners and bookshelf loudspeakers. Dynaco was liquidated in 1980, and the trademark is now owned by Radial Engineering Ltd.

Robert W. (Bob) Carver is an American designer of audio equipment based in the Pacific Northwest.

LEAK is the brand name for high-fidelity audio equipment made by H. J. Leak & Co. Ltd, of London, England. The company was founded in 1934 by Harold Joseph Leak and was sold to the Rank Organisation in January 1969. During the 1950s and 1960s, the company produced high-quality amplifiers, radio tuners, loudspeakers, pickups, tonearms and a turntable. The sale of the business to Rank saw an expanded range of models, and considerable further development of loudspeakers, but Rank was not able to position the brand to counter competition from Japanese electronics manufacturers, so by the late 1970s, electronics and speaker production ceased under the LEAK name.

<span class="mw-page-title-main">Single-ended triode</span> Vacuum tube electronic amplifier that uses a single triode to produce an output

A single-ended triode (SET) is a vacuum tube electronic amplifier that uses a single triode to produce an output, in contrast to a push-pull amplifier which uses a pair of devices with antiphase inputs to generate an output with the wanted signals added and the distortion components subtracted. Single-ended amplifiers normally operate in Class A; push-pull amplifiers can also operate in Classes AB or B without excessive net distortion, due to cancellation.

A valve audio amplifier (UK) or vacuum tube audio amplifier (US) is a valve amplifier used for sound reinforcement, sound recording and reproduction.

Technical specifications and detailed information on the valve audio amplifier, including its development history.

Circlotron valve amplifier is a type of power amplifier utilizing symmetrical cathode-coupled bridge layout of the output stage. Original circlotrons of 1950s used output transformers to couple relatively high output impedance of vacuum tubes to low-impedance loudspeakers. Circlotron architecture, easily scalable, was eventually adapted to operate without output transformers, and present-day commercially produced circlotron models are of output transformerless (OTL) type.

<span class="mw-page-title-main">Tube sound</span> Characteristic quality of sounds from vacuum tube amplifiers

Introduction

<span class="mw-page-title-main">Digital do MaiN</span> Japanese audio engineering company

Digital do MaiN is a Japanese audio engineering company headquartered in Chiyoda, Tokyo, Japan. The company name emphasises symbiosis of analog and digital technologies ; the logo symbolizes an input pin jack, output pin jack and an innovative signal processing unit in between.

The static induction transistor (SIT) is a type of field-effect transistor (FET) capable of high-speed and high-power operation, with low distortion and low noise. It is a vertical structure device with short multichannel. The device was originally known as a VFET, with V being short for vertical. Being a vertical device, the SIT structure offers advantages in obtaining higher breakdown voltages than a conventional FET. For the SIT, the breakdown voltage is not limited by the surface breakdown between gate and drain, allowing it to operate at a very high current and voltage. The SIT has a current-voltage characteristic similar to a vacuum tube triode and it was therefore used in high-end audio products, including power amplifiers from Sony in the second half of the 1970s and Yamaha from 1973-1980. The Sony n-channel SIT had the model number 2SK82 with its p-channel complement named 2SJ28.

Threshold Audio is a high-end audio equipment manufacturer originally established in California in 1974 by audio engineer Nelson Pass and graphic designer René Besne. The company, today based in Houston Texas, manufactures mono-block and stereo power amplifiers, multi-channel power amplifiers and stereo control amplifiers.

<span class="mw-page-title-main">NAD 3020</span> Integrated amplifier by NAD electronics

The NAD 3020 is a stereo integrated amplifier by NAD Electronics, considered to be one of the most important components in the history of high fidelity audio. Launched in 1978, this highly affordable product delivered a good quality sound, which acquired a reputation as an audiophile amplifier of exceptional value. By 1998, the NAD 3020 had become the most well known and best-selling audio amplifier in history.

<span class="mw-page-title-main">Quad Electrostatic Loudspeaker</span> First production electrostatic loudspeaker

The Quad Electrostatic Loudspeaker (ESL) is the world's first production full-range electrostatic loudspeaker, launched in 1957 by Quad Electroacoustics, then known as the Acoustical Manufacturing Co. Ltd. The speaker is shaped somewhat like a home electric radiator curved slightly on the vertical axis. They are widely admired for their clarity and precision, but known to be difficult speakers to run and maintain.

References

  1. ↑ Harley, Robert (August 12, 2015). "Nelson Pass: Four Decades of Innovation". The Absolute Sound. Retrieved August 17, 2022.
  2. ↑ Patents with "Nelson" and "Pass" in the inventor list
  3. 1 2 http://www.diyaudio.com/forums/showthread.php?postid=1600879#post1600879 NP@diyaudio
  4. 1 2 http://stereophile.com/interviews/1191pass/ Interview with NP
  5. ↑ "Magnepan patents".
  6. ↑ http://www.stereophile.com/solidpoweramps/678/index.html Stereophile review of GFA-555
  7. ↑ http://www.audiokarma.org/forums/showthread.php?t=74228 Discussion of Nelson Pass work at Adcom
  8. ↑ "Adcom 555II - Nelson Pass ?". 16 August 2002.
  9. ↑ "Adcom 5800 - Nelson Pass, others". 2 May 2008.
  10. ↑ "Xs Series". Pass Labs.
  11. ↑ Home Theater Geeks 42: DIY Geekfest https://www.youtube.com/watch?v=-h04jeOR3gA
  12. 1 2 Steven R. Rochlin. "SET And SIT Amplifiers Nelson Pass on his exciting new designs. Article By A. Colin Flood". Enjoythemusic.com. Retrieved 2016-07-29.
  13. ↑ Steven R. Rochlin - Superior Audio - Enjoy the Music.com. "First Watt / Pass Labs SIT-2 Stereo Amplifier 10 excellent watts! Review By A. Colin Flood". Enjoythemusic.com. Retrieved 2016-07-29.
  14. ↑ The Pass Zen Amplifier
  15. ↑ http://www.passdiy.com The Pass Labs DIY site
  16. ↑ The DIY Audio site
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