FirstWatt SIT4 is the latest stereo power amp in the lineup. It’s also a 5wpc class A type infused with particular components which make a promise of DHT sonics from a solid-state device

FIRST-WATT F7 - THE AMP YOU DIDN'T EVEN KNOW YOU NEEDED!!

The F8 is a reference tool in the finest sense of the words, excep onally revealing of what comes before it in the playback chain.

The First Watt series of amplifiers started as an exploration of uncommon circuit designs in a low wattage format...

The F7 is a completely different amplifier-animal from my no-gain-of-its-own buffer F4 clone; and yet I was still a bit skeptical that it would have enough power. Nelson didn't seem to hold the same level of reservation.

I’ve always loved listening to music, on the teensy transistor radios I had as a kid, and later with the audio gear I've owned over the years. I learned that with the best gear musical pleasures run deeper.

This is the first time in memory that a distinctly low-power (25Wpc) amplifier has taken top honors, or even placed, in our Product of the Year voting.

There are some definite perquisites from being in the high-performance audio business as long as I have. One of the primary ones has been the opportunity to know some of the “audio legends” and great minds in the audio world.

Every time a new audio technology enters the marketplace, a debate begins about its relative merit

As experienced audiophiles, I’m assuming we all are at least somewhat familiar with Mr. Pass and his work. He’s the chief dude that started companies such as Threshold and later, under his own shingle, at Pass Labs.

I wonder how many audiophiles get caught on the “power escalator,” by which I do not mean the one at the mall, but the one in the listening room.

For more than fifteen years, First Watt has served as Nelson Pass’ creative playground, allowing him to explore unusual low-power designs with an emphasis on sound quality. Most of these designs don’t rank high in terms of commercial appeal.

Something smelt very big fishy. The amps looked like FirstWatt M2, from PCB to chassis to heat sinks to rear panel. But they came from Thailand and were advertised for $850 on eBay.

Here’s a paean to the Nelson Pass designed First Watt B4. This is a superb active two-way crossover. I refer you to a Pdf of the owner’s manual from the First Watt web page for design details:

My wife and I have spent a fair amount of time listening to the F6 and F7. As you know, the purpose of this exercise is to find an amp that can provide a different musical experience from our tube amplifiers.

I just wanted to drop you a note to say how great your coverage of the Munich show was. By far the best I’ve seen. Best, np." This surprise email from Nelson Pass provided the perfect op to inquire about a rumour a reader had shared.

The First Watt F6 offers a fantastic option to anyone in the market to drive sensitive speakers in the 90db’s/8ohms territory and even picks a compelling fight with speakers that are moderately difficult to drive.

The First Watt SIT-1 is a single-ended Class A monoblock power amplifier that uses a single transistor, no feedback, and no output transformer.

On several systems including mine, the SIT-2 did not sound like a tube amplifier. It was better in some respects. Nor did it sound like solid-state either. It was better in many respects there too.

Pass Labs amplifiers have inspired more than a few moments of lust in the hearts of veteran audiophiles. Big, beautiful, powerful, and expensive, their sound, according to some, has advanced the state of the art.

I reached out to Nelson Pass of First Watt this summer and asked the “what’s what with First Watt”. By way of response, Nelson agreed to send me a pair of amps — starting with the J2, a 25wpc (into 8ohms) solid state amp

In August of 2011 I'd reported on a pre-production version of what since has become known as the FirstWatt SIT-2. That nomenclature stands for Static Induction Transistor 2. The extra words channel amp are implied.

The J2 is one of the best amplifiers I’ve heard, regardless of the type of circuit used, and it provides an opportunity to own a product from audio master Nelson Pass at a moderate cost.

While my beloved valve power amps are off being repaired, I thought I should have a 'reliable' standby power amp for everyday listening / backup.

I'm in the process of spending six digits on a small run of special Jfet power amplifiers, my own version of the 'SI' Vfets you may recall from the Yamaha and Sony efforts of the 70s and related to the Digital Do Main product showcased recently on your site.

The F3 surpasses the performance of most tube amps in its ability to remain absolutely quiet while retaining complete control of the lower frequencies.

The First Watt J2 is an absolute honey on amp. Hooked up to my Zu Essence speakers, the sou…

At the going rate, Nelson Pass would soon eclipse our arsenal to demand a 7th moon. For now we could still play ball. Having accompanied his kitchen-table exploits from the 1st through the 5th F amplifiers

The e-mail was from papa. Well, not really. But that's how his many DIY fans refer to Nelson Pass on the DIYAudio forum. The thread on how to build a FirstWatt F5 from scratch has developed into 174 colossal pages by now.

Since my review of the F5, it has since become SET man's favorite transistor amp. As such, it routinely appears in reviews and associated commentary. Off-screen, it also pops up in private e-mails as recommendation to inquiring readers.

First Watt’s latest DIY offering, the B1 buffer stage, is described by Nelson Pass as “a no-feedback JFET buffer that offers ultra low distortion and noise with ultra wide bandwidth.” Nelson’s article may be found here: www.firstwatt.com

First Watt's latest DIY offering, the B1 buffer stage, is described by Nelson Pass as "a no-feedback JFET buffer that offers ultra low distortion and noise with ultra wide bandwidth."

Nelson Pass. FirstWatt. Kitchen table venture. Surely all this has been active long enough to no longer catch our readers in the dark.

The X Factor. In today's game, that's what we call gain. What comes in goes out, simply amplified or enlarged X times. If you strap together an active preamp and an amplifier -- the pervasive combo -- you put together two of those factors for X-squared multiplication.

The First Watt Aleph J is a direct descendant of the Volksamp Aleph 30, itself a descendant of the Pass Labs Aleph 3. The Aleph series was given birth by Nelson Pass and Pass Labs back in 1991.

There's one thing I enjoy about single-ended triode amplifiers, although it isn't so much a characteristic of a good SET as the combination of a good SET amp and an appropriate loudspeaker: They load the room convincingly when the music demands it.

Advancing the art. That requires a lot more than repackaging proven circuits. Or throwing designer parts and boffo face plates at them. Or hype marketing and hyper pricing. Advancement means following the dark paths previously avoided.

Why is an amplifier's first watt so important? Watts are cheap. Don't wurry, be 'appy. In a very fundamental way, the answer to this innocuous question determines the sound of your speaker.

First Watt isn't a real company, and the F1 power amplifier isn't a real product. Consequently, this isn't a real review. Nelson Pass, who founded the Threshold Corporation in the 1970s and continues to operate the successful Pass Labs, also likes to indulge his more radical side as an audio designer.

And now for something totally different. This report is unusual in that it combines a product review with a Do-It-Yourself (DIY) project. There is a very good reason for doing just that , as you will discover shortly.

Current-drive or transconductance amplifiers for consumer audio applications are very rare. One example prior to Nelson Pass' current FirstWatt F-1 model was a design by Be Yamamura intended to be used with his single-driver full-range loudspeaker, both of which at the time were imported into the US by Joe Cohen of now Prana Cable.

Single-ended. Class A. Zero feedback. Fully balanced operation with both RCA and XLR outputs. Noise of 1/10,000,000th of a watt. Input impedance of 80kohm. Output impedance of 80 ohms. Constant draw of 100 wall watts. Output? 10 music watts.

n preparation for my upcoming review of Nelson Pass' new F-1 First Watt current-source amplifier, Nelson asked what speakers I would be using. His whole optimization scheme for the single-driver speaker/amp interface hinges on external compensation networks which are specific to each loudspeaker.

Among the appreciations of DIYers is stuff that works simply, well, and cheap, not necessarily in that order. This project is an effort to assemble these elements into a discrete gain stage that can be used as the front end for modest power amplifiers or as a general audio gain circuit.

About a year and a half ago I released a power supply filter board and thump suppression relay circuit to go with the DIY Sony N channel VFET amplifier kit.

Ten years have passed since the last Speaker Camp Event. I missed it, but I am assured that it was a great success. It featured DIY construction of a Voigt type enclosure holding a Pioneer BoFu 8 inch full range accompanied by a small tweeter to sweeten up the top end.

Limited as it was to about 180 stereo amplifiers, last year's release of designs around the Sony 2SK82 and 2SJ28 Vfet power transistors seems to have been a great success.

The first amp camp goes back almost ten years when a small group of people held the first and only event in Sebastopol California. I had the privilege of designing this little class A amplifier which has proven to be popular among audio DIYers and is currently available in the “store” at www.diyAudio.com

There are a couple of simplifications in this version. We will take advantage of the regulated 12V supply from a standard (cheap) wall-wart which does not have to be very accurate or quiet, just constant DC, and we will adjust the operating point via a small potentiometer P1 for each channel.

This article is the second half of the DIY Sony VFET amplifier project. You will want to treat this as an addendum to Part 1, and probably need to refer to that for some of the information you will want.

This article is the first half of the most recent in a series presenting DIY audio power amplifiers using Static Induction Transistors (SITs), aka VFETs. These are special field effect transistors with a characteristic similar to Triode tubes.

The DIY BIAMP 6-24 kit is a stereo analog active biamp crossover circuit designed for high flexibility. Featuring 12 discrete Jfet buffer circuits operated without negative feedback

This piece was originally presented at the 2019 Burning Amp Festival but was hampered by problems with the projection system. It has been rewritten for Positive Feedback online

In spite of the improvements in efficient Class D switchers, watt-sucking Class A power amplifiers continue to attract high end audiophiles. The breed remains as popular as ever - and why not? Any product of our school system knows that A is better than B, or C or D

At the first Burning Amp Festival in 2007, a young attendee, Nelson Brock and his parents Dana and Liz, displayed a nice pair of loudspeakers using the Pioneer Bofu full range drivers in Voigt enclosures.

This article is a revised version of the original H2 article. It reflects the changes that were made to the circuit for the occasion of the 2019 Burning Amp Festival.

At the Burning Amp Festival 2017 I presented a version of a preamp using the Korg Nutube dual Triode. It is similar to the example circuit provided by Korg, different mostly in the use of Jfet constant current sources instead of bias by resistors.

My friend Nelson Pass is an unusually busy guy, and a long time can pass without word from his secret clifftop lab. He’s also bit of a paradox, equal parts artist and engineer, logical and intuitive, chilled-out and frenetic.

The very first gain device, the vacuum tube Triode, is still made after more than a hundred years, and while it has been largely replaced by other tubes and the many transistor types, it still remains popular in special industry and audio applications.

Historically, audio amplification has been about the elimination of all forms of distortion. Early on, the premise has been that low distortion is one of the keys to audio quality and this was certainly true back when amplifiers had a lot of distortion.

Gifted a box of Korg Nutubes by Mr. Miura of Stereo Sound, I worked up a circuit using them. After some experimentation I decided that the original circuit as suggested in the technical data provided was very suitable, and I made only small adjustments to it:

Many of you are already familiar with Siegfried Linkwitz. I first met him in person at a Burning Amp Festival years ago, and I was able to spend more time with him after I moved to Sea Ranch, where he has a house at the far end of the beach.

This is an addendum to the “Sony SIT AMP part 2” article is the second of a series presenting “Do-It-Yourself” audio power amplifiers using Static Induction Transistors (SITs), also known as VFETs. These are unusual transistors with a characteristic similarity to Triode tubes.

Some discussion came up recently on www.diyaudio.com in the Pass Labs forum regarding the Genesic GA10JT12, a Silicon Carbide junction transistor. I procured some through distribution and tested them in a single-ended Class A amplifier operating in Common Source mode

Thank you all for coming out. I'm out of practice speaking to non-technical audiences, or any audience for that matter, but I get by through having a bunch of pictures strung together to have some sort of arc or lead to some point, which prompt me as to what I'm supposed to be talking about and also distract the audience from my performance.

This article is the second of a series presenting “Do-It-Yourself” audio power amplifiers using Static Induction Transistors (SITs), also known as VFETs. These are unusual transistors with a characteristic similarity to Triode tubes.

This article is the first of a series presenting fairly simple “Do-It-Yourself” audio power amplifiers using Static Induction Transistors. SITs are a rare breed of transistor which have characteristics particularly desired by some audiophiles.

This is about audio power amplifiers, more specifically about those made with a special type of transistor known originally as a VFET, now more commonly referred to as a Static Induction Transistor (SIT).

When I was young, in the halcyon age of the late 50's and early 60's, I spent my Saturdays at the one of the two local theaters watching “B” science fiction and horror movies.

The Burning Amp Festival is a DIY audio event held in San Francisco in October for the past few years. This is a loose transcription of Pass talking without notes but with pictures. Edited for clarity and brevity and to make Pass sound more articulate than he really is.

Do-It-Yourself audio is a great activity. Many major audio components are easily constructed and made to perform as well or better than what we see in the stores and at considerable savings.

In the Volume 0 of Linear Audio I presented a redux of the 1985 Hiraga design, the Nemesis. The article explored some of the issues and variations that accompany the use of a simple single-ended Class A design coupled to the loudspeaker through an output transformer.

Since I first encountered them in the mid '70's I have always admired the JBL L300 Summit loudspeakers. I have always thought these were some of the most attractive loudspeakers ever made, and I recalled that they sounded as good as they looked.

Five years ago I launched the F5 power amplifier project which culminated in a production run of 100 amplifiers and a DIY article. It has proven to be a popular design, and as of this writing approaches 2 million views on DIYAudio.com.

In the mid 1970's a special variety of Jfet invented in Japan called a Static Induction Transistor (SIT) found its way into the “Vfet” power amplifiers produced by Yamaha and Sony.

In the BA-1 and BA-2 projects we constructed two different amplifiers using very similar input and voltage gain stages (aka the “front ends”), but used them to drive two different Class A Mosfet follower output stages.

In 1972 I had the good fortune to begin working for ESS, arriving a few weeks before they met Oskar Heil and his air motion transformer design. You can imagine the excitement that followed.

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 output

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 simplicity thing can get a little of of hand.

The third annual Burning Amp Festival was held in San Francisco last October, drawing a couple hundred DIY Audio enthusiasts, many from long distances.

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 of loudspeakers, or the fortuitous combination of components which complement each other perfectly.

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, and rub shoulders with the rich and famous.

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 bay area.

Audiophiles seem to revel in minor controversies – vinyl vs CD's, tubes versus solid state, capacitor, wires, magic dots... and negative feedback.

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 us need or want. At least 10 db more.

B1 Gerber Files

The meters on our amplifiers are different. They reflect the current consumption of the amplifier, and when the amplifier is operating, they don’t go down to zero like the meters on other amplifiers.

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 JFET itself, and except for a cascode transistor the rest of the amplifier used only passive components.

During the past few years a number of excellent designs have been published for domestic audio amplifiers. However, some of these designs are now rendered obsolescent by changes in the availability of components

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.

Conventional wisdom holds that a pure voltage source amplifier is ideal for audio applications, and generally designers of loudspeakers work to that assumption.

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.

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 feet long with a 42 Hz expansion curve and a 50 sq ft mouth.

f 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 with it further.

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 watts out).

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 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 circuits are inevitably composed of collections of simple circuits

The aesthetic appeal of a single wide-bandwidth loudspeaker driver is obvious in its simplicity. There are no crossover networks, little or no phase shift versus frequency, and a single acoustic source location.

If you have access to a minimal number of wood working tools, these cabinets are quite easy to build. While they can be constructed with rebate joints or biscuits, we have designed a simple way to assemble the parts by using a small number of simple miters and butt joints.

The quality of individual parts is a particular concern to audio “do-it-yourselfers” (henceforth known as DIYers). Many of them lay awake at night agonizing over choices of capacitors, resistors, wires

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 of it is wildly optimistic.

Sometimes two designs complement each other so well that you are surprised they weren’t invented together. So it is with the X Super- Symmetric amplifier and the Aleph single-ended Class A output circuit.

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 2 through 4 of the Zen Variations

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.

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.

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.

Lots of people don't understand electricity, but they do understand plumbing. Hydraulics provides a good analogy in understanding basic electrical flow.

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 design is still available.

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 the decision as to how much you will actually

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 noise.

The popularity of the Zen projects points out the interest in very simple linear circuits. They are intended to fuel that interest.

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

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 there something fundamental about this kind of design

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 class A power amplifier using a single MOSFET gain stage.

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 opportunity?to build another 25 copies of the amplifier, listen to it on a larger variety of loudspeakers

There are two most essential principles to audio amplifier design. The first is simplicity. The second is linearity. Einstein said, "Everything should be made as simple as possible, but no simpler."

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 current. The greatest variations occur here, and it is necessary to do some matching to get proper performance.

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 left as an exercise to the reader.

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 initiating such a project.

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 as the input signal).

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

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.

Lowering distortion in power circuits without compromising their transient response remains a primary problem for designers of audio power amplifiers.

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 as a demonstration of technical prowess

In spite of their high cost and low efficiency, class A power amplifiers have recently been receiving more attention from audiophiles who demand uncompromising accuracy.