Nelson Pass

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Nelson Pass (born June 27, 1951) is a designer of audio amplifiers. [1] Pass is vocal that listening tests remain valuable and that electrical measurements alone do not fully characterize the sound of an amplifier. [2] Pass holds at least seven U.S. patents related to audio circuits. [3]

Contents

Career

Studies, PMA and ESS

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

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. [5] 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. [7] [8] Nelson also designed the GFA-5XXX MOSFET-based series of high-bias class-AB amplifiers for Adcom (i.e. -5300, -5400, -5500, -5800). [9] [10]

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, [11] 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. [12] [13] 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. [13] 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. [14]

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. [15] [16] [17] His nickname among the DIY audio community is "Papa".

Design characteristics

Typically using MOSFETs as the gain devices, (often as current sources rather than voltage sources), most of his designs operate in Class A, with all the low distortion of small signal benefits generally associated with that. He is also known for his advocacy of "minimalist" designs, which reduce the circuit complexity and number of components through which the audio signal must travel, resulting in any residual distortion having a very simple distortion spectrum. His more powerful designs that go beyond what can practically be realized in Class A (such as the Threshold and Pass Labs products) operate in Class AB1 but retain a heavy bias so that they operate in Class A during quieter passages, and great emphasis has been given to avoiding or minimizing switching effects.

Related Research Articles

<span class="mw-page-title-main">Amplifier</span> Electronic device/component that increases the strength of a signal

An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal. It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its gain: the ratio of output voltage, current, or power to input. An amplifier is defined as a circuit that has a power gain greater than one.

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

An audio power amplifier is an electronic amplifier that 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">Electrostatic loudspeaker</span> Sound playback device

An electrostatic loudspeaker (ESL) is a loudspeaker design in which sound is generated by the force exerted on a membrane suspended in an electrostatic field.

<span class="mw-page-title-main">Valve amplifier</span> Type of electronic amplifier

A valve amplifier or tube amplifier is a type of electronic amplifier that uses vacuum tubes to increase the amplitude or power of a signal. Low to medium power valve amplifiers for frequencies below the microwaves were largely replaced by solid state amplifiers in the 1960s and 1970s. Valve amplifiers can be used for applications such as guitar amplifiers, satellite transponders such as DirecTV and GPS, high quality stereo amplifiers, military applications and very high power radio and UHF television transmitters.

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

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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, a well-known figure in the high-end audio community. The company was founded in 1991.

Founded by David Hafler and Ed Laurent in Philadelphia, Pennsylvania in 1955, 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.. Its 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.

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

Tube sound is the characteristic sound associated with a vacuum tube amplifier, a vacuum tube-based audio amplifier. At first, the concept of tube sound did not exist, because practically all electronic amplification of audio signals was done with vacuum tubes and other comparable methods were not known or used. After introduction of solid state amplifiers, tube sound appeared as the logical complement of transistor sound, which had some negative connotations due to crossover distortion in early transistor amplifiers. However, solid state amplifiers have been developed to be flawless and the sound is later regarded neutral compared to tube amplifiers. Thus the tube sound now means 'euphonic distortion.' The audible significance of tube amplification on audio signals is a subject of continuing debate among audio enthusiasts.

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.

References

  1. ↑ Harley, Robert (August 12, 2015). "Nelson Pass: Four Decades of Innovation". The Absolute Sound. Retrieved August 17, 2022.
  2. ↑ http://www.herronaudio.com/images/Measurements.pdf Friend or Foe? High End Designers Reassess the Importance of Audio Measurements
  3. ↑ Patents with "Nelson" and "Pass" in the inventor list
  4. 1 2 http://www.diyaudio.com/forums/showthread.php?postid=1600879#post1600879 NP@diyaudio
  5. 1 2 http://stereophile.com/interviews/1191pass/ Interview with NP
  6. ↑ "Magnepan patents".
  7. ↑ http://www.stereophile.com/solidpoweramps/678/index.html Stereophile review of GFA-555
  8. ↑ http://www.audiokarma.org/forums/showthread.php?t=74228 Discussion of Nelson Pass work at Adcom
  9. ↑ https://www.diyaudio.com/community/threads/adcom-555ii-nelson-pass.5280/
  10. ↑ https://www.diyaudio.com/community/threads/adcom-5800-nelson-pass-others.122372/page-2
  11. ↑ "Xs Series". Pass Labs.
  12. ↑ Home Theater Geeks 42: DIY Geekfest https://www.youtube.com/watch?v=-h04jeOR3gA
  13. 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.
  14. ↑ 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.
  15. ↑ The Pass Zen Amplifier
  16. ↑ http://www.passdiy.com The Pass Labs DIY site
  17. ↑ The DIY Audio site
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