Project Categories List

A40 Part Substitutions / Nelson Pass / 2000

After 22 years, it appears that quite a few DIY enthusiasts are still eyeing the A40 Class A amplifier design, but are discovering that not a single transistor from this… More...

A75 Part 1 / Norman Thagard & Nelson Pass / 1992

READERS' REQUESTS FOR more power are reasonable, but not interesting enough to justify another article. Hanging some output transistors on the original and beefing up the power supply is best… More...

A75 Part 2 / Norman Thagard & Nelson Pass / 1992

THE STORY BEHIND the A75 power amplifier continues. In Part I, we discussed its origins and direct predecessor, the Pass A40, as well as some general guidelines to follow before… More...

Amp Camp Project / Pass DIY / 2016

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Build a MOSFET Citation 12 / Nelson Pass / 1981

Audio Amateur has published a number of projects modifying popular kits, usually Dynaco's. Obviously it is much less expensive to use the chassis and power supply, pots, connectors, switches, PC… More...

Build The Amazing FET Circlotron / Michael Rothacher / 2008

Cue the Theremin music! This article is about building your own all-FET Circlotron. It smashes atoms. No, strike that. It won’t smash atoms like a cyclotron, but it has a… More...

Cascode Amplifier Design / Nelson Pass / 1978

Lowering distortion in power circuits without compromising their transient response remains a primary problem for designers of audio power amplifiers. Until fairly recently, the favorite technique for removing distortion components… More...

Construct a Class - A Amplifier / Nelson Pass / 1977

Most audio power amplifiers use class A circuitry except in the drive and output stages, where they use class B or AB operating modes to achieve high efficiency. In class… More...

Current Source Amplifiers and Sensitive Full Range Drivers / Nelson Pass / 2004

Conventional wisdom holds that a pure voltage source amplifier is ideal for audio applications, and generally designers of loudspeakers work to that assumption. This belief has particularly been dominant since… More...

DIY Op Amps / Nelson Pass / 1998

Carl Sagan observed, "If you want to make an apple pie from scratch, you must first create the universe." If you want to build an audio circuit, you will make… More...

Son of Zen / Nelson Pass / 1997

The Zen has proven to be a popular and enduring do-it-yourself amplifier. The design addresses the audiophile's enthusiasm for singleended amplification, but is even more interesting for its exploration of… More...

The Amazing FET Circlotron Construction, Continued / Michael Rothacher / 2008

A lot of would-be audio projects die on the vine, even when printed circuit boards and components are readily available. The planning, layout, and construction of the chassis metalwork are… More...

The Pass A-40 Power Amplifier / Nelson Pass / 2000

FLATTERED BY THE opportunity to publish a project circuit, the designer is often beset by seemingly contradictory considerations. On the one hand, it is tempting to design a complex circuit… More...

The PLH Amplifier / Nelson Pass / 2005

In 1969 John Linsley-Hood wrote in Wireless World: During the past few years a number of excellent designs have been published for domestic audio amplifiers. However, some of these designs… More...

The Zen Amplifier / Nelson Pass / 1993

I. "What is the sound of one transistor clapping?" There are two most essential principles to audio amplifier design. The first is simplicity. The second is linearity. Einstein said, "Everything… More...

Zen Amplifier Revisited / Nelson Pass / 1994

I must say that I have been very gratified by the response to the Zen amplifier from the last issue of TM. Since writing the article I have had an… More...

Zen Variations 1 / Nelson Pass / 2001

As an exploration into the potential performance of a very simple amplifier, the Zen amplifier has succeeded in creating notoriety and some controversy over the last 8 years. More importantly,… More...

Zen Variations 2 / Nelson Pass / 2002

Welcome back to the Zen Amp Variations. This is part 2 of many parts in which we explore some of the ways to make a very simple audio amplifier. In… More...

Zen Variations 3 / Nelson Pass / 2002

In Part 2 we developed a new active current source for the Zen amplifier. In this part, we create a power supply regulator suitable for the Zen amplifier projects. Previous… More...

Zen Variations 4 / Nelson Pass / 2002

The Penultimate Zen is the sum of several incremental improvements to the original Zen amplifier of 1994. Eight years just flies by, doesn’t it? These improvements are contained in parts… More...

Zen Variations 5 Hi Res / Nelson Pass / 2003

The Zen Amp concept is an exploration of how well you can make a simple audio amplifier perform. It makes for an interesting illustration of design technique, since more complex… More...

Zen Variations 5 Low Res / Nelson Pass / 2003

The Zen Amp concept is an exploration of how well you can make a simple audio amplifier perform. It makes for an interesting illustration of design technique, since more complex… More...

Zen Variations 6 / Nelson Pass / 2004

U.S. Patent # 5,376,899 describes an amplifying circuit topology that takes advantage of the character of matched balanced amplifiers that are cross-coupled to provide cancellation of distortion and noise. The… More...

Zen Variations 7 / Nelson Pass / 2004

One of the performance issues raised by the original Son of Zen (Audio Electronics, #2, 1997) was its efficiency figure, which was charitably described as 4% (500 watts in, 20… More...

Zen Variations 8 / Nelson Pass / 2005

Thanks to a nice person on the Pass Labs Forum ( www.diyaudio.com ), I became aware that high current power JFET transistors are again available. You can check them out… More...

Zen Variations 9 / Nelson Pass / 2006

In ZV8 we dipped our toes into the waters of power JFET transistors using the new Lovoltech LU1014D in a simple circuit. The focus of the project was on the… More...

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