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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Arch Nemesis / Nelson Pass / 2010

A poster of Einstein once said, “Things should be made a simple as possible, but no simpler”. This can apply to audio amplifiers, but if they are evaluated subjectively, the… More...

Audio, Distortion and Feedback / Nelson Pass / 2008

Audiophiles seem to revel in minor controversies – vinyl vs CD's, tubes versus solid state, capacitor, wires, magic dots... and negative feedback. At one extreme, the position is that “feedback… More...

B1 Buffer Preamp / Nelson Pass / 2008

Side A So here we are in the New Millennium, and thanks to Tom Holman and THX we’ve got lots of gain in our electronics. More gain than some of… More...

Balanced Zen Line Stage / Nelson Pass / 1997

The popularity of the Zen projects points out the interest in very simple linear circuits. They are intended to fuel that interest. The Zen, Bride of Zen, and Son of… More...

Bride of Zen / Nelson Pass / 1994

This is the second installment of a trilogy of construction projects centered around the performance obtainable from absolutely minimalist circuitry. Part one described the Zen amplifier, a 10 watt single-ended… More...

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...

Burning Amplifier # 1 / Nelson Pass / 2009

The Burning Amp Festival is an event every October in San Francisco. Do-it-yourself audio enthusiasts from all over gather to show off their projects, listen to talks and equipment demos,… More...

Burning Amplifier # 2 / Nelson Pass / 2009

In Burning Amp 1 we examined an amplifier circuit designed to complement the hardware we gave away to some attendees at last October's Burning Amp Festival in the San Francisco… 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...

Current Source Crossover Filters / Nelson Pass / 2004

In today’s marketplace, audio power amplifiers are conventionally viewed as voltage sources, delivering a given voltage at the output that is a multiple of an input voltage. To the extent… 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...

Ground Loops / Kent English / 2002

Your brand new component is hooked up, fresh from the box, and the fi rst time you power it up is a sonic disaster; it hums, it buzzes and in… More...

Leaving Class A / Nelson Pass / 2008

The meters on our amplifi ers are different. They refl ect the current consumption of the amplifi er, and when the amplifi er is operating, they don’t go down to… More...

Like Peanut Butter and Chocolate / Nelson Pass / 2002

Pass Labs XA Series Power Amplifiers For over ten years, the Aleph series of single-ended Class A amplifi ers have received praise for their outstanding sonic defi nition, warmth, and… More...

Matching Devices / Nelson Pass / 1993

After you acquire the devices, you will need to test them. You might consider running lots of tests on these transistors, but only one is essential: measuring gate-source voltage versus… More...

Miscellaneous Projects / Webmaster / 2013

Here are some great project-submissions folks wanted to show-off.  They don't directly correspond with a single PassDIY project, but we still fealt like they should have a home.  Great work… More...

Pearl 2 / Wayne Colburn / 2010

Here is the long awaited sequel to the Pearl phono stage, named after my maternal Grandmother who was good with a sling shot , played piano and organ and occasionally… More...

Phase -Coherent Crossover Networks / Nelson Pass / 1982

The importance of phase response in the audio chain has been brought to greater focus recently by equipment claims of phase coherency, (the output signal has the same phase relationships… More...

Power Supplies / Nelson Pass / 2001

Lots of people don't understand electricity, but they do understand plumbing. Hydraulics provides a good analogy in understanding basic electrical flow. Wire is a pipe. Water pressure is voltage. Water… More...

Single Ended Class A / Nelson Pass / 1995

Single-Ended Class A amplifiers have certainly hit it big in the four years since we began testing the first Aleph 0. So is this just another audio fad, or is… More...

Soldering Tips / Karen Douglass / 2004

PCBoard Soldering can be a kind of art form, when done properly. The result should be a perfect physical and electrical connection, between the part lead and the solder pad… 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...

Speaker Cables / Nelson Pass / 1980

AUDIOPHILES RECENTLY BEGAN re-examining the performance of every link in the audio playback chain, and before long their attention turned to the lowly loudspeaker cable. In response to demand, a… More...

Super-Symmetric Amplification / Nelson Pass / 1998

U.S. Patent # 5376899 describes a new amplifying circuit topology that takes advantage of the character of special matched balanced amplifiers that are cross-coupled to provide cancellation of distortion and… 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 Kleinhorn Part 1 / Nelson Pass / 2004

33 years ago I decided to build a big horn system. Constructed in the dorm library over Christmas break, the result was dubbed The Claw, a straight exponential horn 9… More...

The Kleinhorn Part 2 / Nelson Pass / 2004

If you saw part one of this project (AudioXpress, January 2005), you know that the KleinHorn is a big toy, and you can imagine that it’s hard to resist playing… More...

The Legend of EL PIPE-O / Kent English / 2002

Most woofers just don’t quite do the lowest octave. You read the specs that say “usable response: 20 Hz – 20 KHz” and you know that the 20 Hz part… 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 Sweet Spot / Nelson Pass / 2009

Every audiophile understands the concept of the “sweet spot”, that happy balance of conditions that elicits the best possible sound. It can be a particular listening spot, the best positioning… 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...

Trouble Shooting / Kent English / 2002

Pre-Amplifiers Within the Pass Labs pre-amplifier family we typically see two installation errors, both involving cable issues. The most common error concerns improper sequence of cable connection for our pre-amplifiers… 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 I/V Converter / Nelson Pass / 2010

Thirteen years ago Pass Labs launched the D1, a dedicated Digital to Analog converter for high end audio. It was based on balanced PCM63 DAC chips with a current source… 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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