Semantic Coherence: First Watt – Signal Evidence & AI Readability

[H2] passlabs.com

[H2] passdiy.com

[H2] Watt's the Deal?

Dick Olsher famously remarked that “The first watt is the most important watt.” This sentiment has also been expressed by others as “Who cares what an amplifier sounds like at 500 watts if it sounds like crap at one watt?” With this in mind, I created First Watt in 1998 as a “kitchen-table” effort, exploring unusual low power amplifiers with an emphasis on sound quality.Small amplifiers have a number of advantages over “big iron” in that very high quality can be achieved with simple Class A circuits using little or no feedback.There is no such thing as a perfect amplifier. All audiophiles and their associated equipment have specific needs, but in each case there is such a thing as a best amplifier – the one that makes you happy.First Watt exists because I wanted to explore a variety of amplifier designs in what I think of as neglected areas – amplifiers that might not fit into the mainstream and are probably not appropriate to my more commercial enterprise, Pass Labs.With oddball characteristics and output power ratings of 25 watts or less, First Watt is not for most people. If you have efficient loudspeakers, listen at reasonable levels and are obsessed about subjective performance, then you probably have come to the right place.

If you want reliable audio product, then you really have come to the right place. For twelve years First Watt has had a near-zero failure rate.First Watt amplifiers are routinely compared with tube amplifiers, although I make a point that they are not designed to mimic tubes as such. These amplifiers share some of the characteristics of the better tube products in that they have simple circuits with minimal or no feedback and emphasize performance of individual gain devices. In some ways they are better than tubes, in other ways perhaps not.With the new releases of the SIT-1, SIT-2, B2 and B4, the total is now up to sixteen designs released, all simple Class A circuits, each offering a unique approach to sonic quality. The F1 and F2 are both current source (as opposed to voltage source) amplifiers with no feedback. The F3 offers single-stage single-ended operation with new Jfet power transistors. The F4 is a push-pull current buffer with no voltage gain or feedback, and the F5 is a uniquely high performance push-pull amplifier with feedback. The J2 and M2 continue to push the envelope in unique ways.And there is more to come.

[H2] Watt's New?

24/10/2023

[H2] First Watt SIT-4

The SIT-4 is the First Watt power amplifier using the industrial grade Static Induction Transistors.  It is preceded by the ground breaking SIT-1, 2, and 3 and follows their technical philosophy and construction.

SIT-4 Power Amplifier

8/4/20

[H2] First Watt F8

Originally created almost 6 years ago, the F8 is a stereo two-stage single-ended Class A amplifier using the NOS Toshiba 2SJ74 P channel Jfets and SemiSouth R100 SiC power Jfets for signal gain, plus IRFP240 Mosfet mu-follower current sources, for a total of three devices per channel.

F8 Power Amplifier

11/1/21

[H2] First Watt SIT-3

The SIT-3 is the very latest example of single-ended / single-stage Class A amplifiers using the SIT (aka VFET) power transistor exclusive to First Watt. It is preceded by the successful SIT-1 and SIT-2 and very much follows their technical philosophy and construction.

SIT-3 Power Amplifier
Owner Manual SIT-3 Power Amplifier

4/1/21

[H2] First Watt F7

The F7 is a very unique power amplifier, a two-stage push-pull JFET/MOSFET topology with fewer parts than any First Watt amplifier to date and incorporating a very interesting balance of very low negative voltage feedback and a little bit of positive current feedback to give an astonishing measure of control over reactive loudspeaker loads.

F7 Power Amplifier

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[H2] LET’S

[H2] TOUCH

[H2] GET IN

Everybody gets a reply, but the volume is high and it might take a while, especially if I’m at the beach. If you don’t get a response within 2 weeks, send it again.

[H2] Related sites

[H2] passlabs.com

[H2] passdiy.com

Pass Laboratories     (530) 878 5350     [email protected]

[H2] Products

[H2] I spend a lot of time building and evaluating basic amplifier concepts with an eye toward producing the highest quality sound with elegantly simple circuits.

There is no such thing as a perfect amplifier, but there is a best amplifier for each type of speaker, music, and listener. Each First Watt piece is a unique design and is “best” in some particular way. They look alike because they all use the same basic chassis and power transformer. On the up side, it makes it easy for me to test ideas and compare different designs with the hardware being a fixed constant.Looking for tomorrow’s faceplate with yesterday’s circuits?You’re in the wrong place.

AMPLIFIER COMPARISON CHART (Click on the product name in the left column for more information)

Model
Stereo/Mono
Output8 Ohm
Output4 Ohm
Feed-back
Output Ohms
Input Ohms
Input Bal/SE
Distortion %
Noise UV
GAINdB
Mosfet / Jfet / SIT
SE PP
Available New?

SIT-5

M

35w

60w

N

0.25

100K

SE

0.1

36

19

S/M

SE

SIT-4

S

10w

5w

N

4

100K

SE

0.6

75

20

S

SE

F8

S

25w

15w

Y

0.2

100K

SE

0.02

100

15

J

SE

SIT-3

S

18w

30w

N

0.26

200K

SE

0.2

50

11.5

S/M

DEF

F7

S

20w

30w

Y

0.08

10K

SE

0.05

100

14

M

PP

F6

S

25w

50w

Y

0.5

100K

SE

0.05

200

14

M

PP

SIT-1

M

10w

8w

N

4

100K

SE

0.6

100

18

S

S

SIT-2

S

10w

8w

N

4

100K

SE

0.6

100

18

S

S

J2

S

25w

13w

Y

0.4

100K

Both

0.03

100

20

J

S

M2

S

25w

40w

N

0.4

100K

SE

0.05

500

15

M

P

F5

S

25w

40w

Y

0.1

100K

SE

0.01

100

15

M

P

F4

S

25w

40w

N

0.2

47k

SE

0.05

50

0

M

P

F3

S

15w

10w

Y

1

10K

SE

0.01

50

12.5

J

S

F2

S

5w

10w

N

15

50k

SE

1

30

14

M

S

F2J

S

5w

10w

N

15

10K

SE

0.3

30

14

J

S

F1

S

10w

7w

N

80

100K

Both

0.1

30

15

M

BS

F1J

S

10w

7w

N

60

10K

Both

0.05

30

15

J

BS

Aleph J

S

25w

13w

Y

0.4

240K

Both

0.05

100

20

M

S

[H2] Notes:

Distortion figures are at 1 watt into 8 ohms at 1 Khz. See the specific product information for more detail.Noise figures are unweighted from 20 Hz to 20 Khz.For Damping Factor, divide 8 by output ohms, for example, 8 ohms / 0.4 ohms = 20Bal/SE means XLR and/or RCA input connectors.F1, F1J, F2, F2J, F3, SIT-1 and SIT-2 are single gain stage amplifiers. The others have two stages.Mosfet/Jfet refers to the output transistors. Two-stage amps with Mosfet outputs have Jfet input devices.All amplifiers are available in 240 or 120 volts AC. Consumption ranges from 160 to 200 watts. All amplifiers operate at temperatures between 45 and 55 deg C.

[H2] Line Stage Products

As with the amplifiers, at one point I ordered up a bunch of metal to put line level electronics in. Here’s what has occurred so far, some of these still in progress.

[H2] B1

No longer available

A stereo buffered passive volume control with two inputs. The buffer circuit is a simple Jfet follower operated with no feedback.

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[H2] B2

No longer available

A stereo buffered bi-amp splitter with relative level adjustment for high and low power amplifiers. If you are bi-amping it is very likely that you need this.

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[H2] B3

No longer available

A stereo gain stage with one pair of inputs, two level controls and a high gain / high voltage swing stage with no feedback. Suitable as a front end for power follower amplifiers and also for bridging and/or isolation.

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[H2] B4

No longer available

A stereo active crossover with adjustable frequencies, slopes, and level. Active circuitry is provided by Jfets operated with no feedback.

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[H2] B5

No longer available

A stereo active crossover with adjustable frequencies, slopes, and level. Like the B4 but filters and equalization for full-range drivers with woofers in open baffles.

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[H2] FAQ

[H2] Q: Why would I want one of these?

A: Maybe you don’t. These amplifiers are all out of the mainstream, reflecting quality in simplicity and intrinsic linearity, often with little regard for the usual performance specifications. I presume a subset of audiophiles will appreciate them.

[H2] Q: What about all the other amplifiers that measure better?

A: The ear is not a microphone, the brain is not a tape recorder, and measurements are limited in describing subjective quality. I like to have low distortion and so on, but these things take a back seat to what I experience when I listen. There are plenty of products which have great specs – I will not be offended if you buy those.

[H2] Q: Why such simple circuits?

A: It is my experience that simple linear circuits tend to sound better. I think they are more interesting and subtle than complicated circuits, and I find that measurements and subjective sound quality correlate better with simple gain paths. Exploring their potential for high performance is what I like to do.

[H2] Q: Why do they run hot?

A: They are Class A amplifiers. They are very linear, but they run hot. Can I make them sound good without Class A? No. Because they run hot, it is important that they get good ventilation. Do not place them in a closed cabinet or on top of another hot amplifier.

[H2] Q: Isn't Class A bad for the environment?

A: Everything is bad for the environment, in case you haven’t noticed. When I look at the cost of enjoying my 25 watt/ch class A amplifier as compared to watching a big screen television or running a porch light all night, I see that I get as much or more value for the same sort of consumption. If I drive down the hill to shop at Fry’s, I consume about as much power as running one of my amplifiers for 2 hours a day for a year. So I go to Fry’s less often, and I turn the amp off when I’m done.

[H2] Q: What's so bad about feedback?

A: Feedback isn’t so bad. Sometimes I use it, sometimes I don’t. It all depends on what makes a particular design sound better. In the ideal case, we wouldn’t need feedback to improve the performance, but our parts are not ideal.

[H2] Articles & Reviews

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[H5]

[H5] Products

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Articles
Reviews

2024SIT 4 – HiFi Knights – Dawid GrzybFirstWatt 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 deviceRead More2024F7 – ABX-Audiophile – James OwensFIRST-WATT F7 - THE AMP YOU DIDN'T EVEN KNOW YOU NEEDED!!Read More06-15-2021F8 – The Absolute Sound – Dick OlsherThe F8 is a reference tool in the finest sense of the words, excep onally
revealing of what comes before it in the playback chain.Read More03-28-2017F7 – Positive Feedback – John HoffmanThe First Watt series of amplifiers started as an exploration of uncommon circuit designs in a low wattage format...Read More01-29-2017F7 – Positive Feedback – Gary BeardThe 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.Read More11-19-2016F7 – CNET – Steve GuttenbergI’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.Read More11-2016J2 – Stereophile Amplifier of the YearThis 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.Read More10-04-2016F7 – Audiophile Review – Steven StoneThere 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.Read More09-20-2016J2 – Stereophile Review – Herb ReichertEvery time a new audio technology enters the marketplace, a debate begins about its relative meritRead More09-09-2016F7 – Part-time Audiophile – John RichardsonAs 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.Read More08-2016F6 – Dagogo – Doug SchroederI 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.Read More06-28-2016F7 – Absolute Sound – Dick OlsherFor 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.Read More02-2016F7 – 6moons – Srajan EbeanSomething 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.Read More2016B4 – Tom CraggsHere’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:Read More2016F7 – Dave BanowetzMy 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.Read More09-2014F6 – 6moons – Srajan EbeanI 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.Read More2014F6 – New Record Day – Ron BrenayThe 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.Read More11-2013SIT-1 – Dagogo – Jack RobertsThe First Watt SIT-1 is a single-ended Class A monoblock power amplifier that uses a single transistor, no feedback, and no output transformer.Read More08-2013SIT-2 – Enjoy The Music – A. Colin FloodOn 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.Read More11-15-2012J2 – Ultra AudioPass 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.Read More10-08-2012J2 – Part Time Audiophile – Scott HullI 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 ampRead More06-2012SIT-1 – 6moons – Srajan EbeanIn 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.Read More2012J2 – SoundstageThe 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.Read More10-31-2011Aleph J – Greg HumphriesWhile my beloved valve power amps are off being repaired, I thought I should have a 'reliable' standby power amp for everyday listening / backup.Read More08-2011SIT-2 – 6moons – Srajan EbeanI'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.Read More07-22-2011F3 – Tone AudioThe F3 surpasses the performance of most tube amps in its ability to remain absolutely quiet while retaining complete control of the lower frequencies.Read More07-22-2011J2 – Tone Audio – Steve GuttenbergThe First Watt J2 is an absolute honey on amp. Hooked up to my Zu Essence speakers, the sou…Read More10-2009J2 – 6moons – Srajan EbeanAt 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 amplifiersRead More07-2009F5 – 6moons – Srajan EbaenThe 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.Read More06-2009F5 – 6moons – EdSince 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.Read More10-16-2008B1 – Black Dahlia – Dick OlsherFirst 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.comRead More07-2008B1 – Enjoy the Music – Dick OlsherFirst 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."Read More05-2008F5 – 6moons – Srajan EbaenNelson Pass. FirstWatt. Kitchen table venture. Surely all this has been active long enough to no longer catch our readers in the dark.Read More09-2007F4 – 6moons – Srajan EbaenThe 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.Read More01-2006Aleph J – 6moons – Michael LavorgnaThe 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.Read More12-24-2005F2 – Stereophile – Art DudleyThere'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.Read More11-2005F3 – 6moons – Srajan EbaenAdvancing 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.Read More07-2005F2 – 6moons – Srajan EbaenWhy 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.Read More01-30-2005F1 – Stereophile – Art DudleyFirst 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.Read More12-2004F1 – Enjoy the Music – Dick OlsherAnd 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.Read More10-2004F1 – 6moons (setup)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.Read More10-2004F1 – 6moons (performance) – Srajan EbaenSingle-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.Read More08-2004F1 – 6moons (concept)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.Read MoreArticle 2022DIY Front End 2022Among 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.Read MoreArticle 2022DIY Power Supply Filter and Thump RelayAbout 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.Read MoreArticle 2022Speaker Camp 2022Ten 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.Read MoreArticle 2022Sony VFET OS2Limited 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.Read MoreArticle 2021DIY ACA miniThe 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.comRead MoreArticle 2021DIY H2 Generator v2There 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.Read MoreArticle 2021DIY Sony VFET pt 2This 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.Read MoreArticle 2021DIY Sony VFET pt 1This 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.Read MoreArticle 2020DIY Biamp 6-24 CrossoverThe 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 feedbackRead MoreArticle 2020The Square LawThis 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 onlineRead MoreArticle 2019Leaving Class A 2019 reduxIn 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 DRead MoreArticle 2019ACP+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.Read MoreArticle 2019H2 Harmonic Generator - RevisedThis 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.Read MoreArticle 2019DIY Nutube PreampAt 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.Read MoreArticle 2018FAOW-V2 by Mike RothacherMy 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.Read MoreArticle 2018The Venerable TriodeThe 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.Read MoreArti