ELEVATE YOUR EXPERIENCE
PREAMPLIFIERS
Xs Series Preamps
Ultra High-End Preamp & Phono
When we began development of the Xs power amplifier five years ago, we knew that we would also need a companion piece.
We were given “carte blanche” on the design and an unlimited budget, the result of this is the Xs Preamp.
True “dual-mono” design
only component shared between channels other than casework, being the AC power connection to house power
Control section
includes its own regulated power supply
Minimal noise
Negligible channel to channel “cross-talk”
Xs Preamp Dual Chassis Preamp – $38,000
This large, dual-chassis preamplifier is built in true dual-mono arrangement. Each channel has its own power supply board with over 100,000uf of capacitance for unfettered transient response. Noise levels have been dropped from the already low-noise XP30. Refined circuit design and layout, new gain-stages with auto-bias and DC compensation all combine for optimal performance. But it all comes down to sound; once you listen to the Xs preamplifier, there is no going back.
Technical specifications
Awards and Reviews
Editors’ Choice Award 2017
The Absolute Sound
“For me, the Xs series has drawn a line in the sand and has redefined the ‘state of the art’.”
“Have a sound that is almost beyond description in words.”
Circuitus Maximus Award 2017
Top o’ the line Brutus Awards 2017
Xs Phono Dual Chassis Phono – $45,000
The Xs Phono preamplifier represents an all-out assault on the state-of-art in Vinyl and the most intensive and difficult design effort made at Pass Laboratories. The final product of this massive effort extracts the utmost performance from a simple topology and operates with the extremely small and delicate signals coming from today’s wide variety of phono cartridges. The result is music that emerges from a quieter background and blooms into a richer, more precise soundstage.
Technical specifications
XP Series Preamplifiers
High-End Preamps
The Pass Laboratories XP-10, XP-20 and XP-30 preamplifiers are the natural descendants to the long lived, highly acclaimed and successful X series of Pass Laboratories line-stages.
Dynamic sound
The XP preamplifiers sound more dynamic, bass lines are more clearly, cleanly and accurately delineated
Clear bass lines
cleanly and accurately delineated
Fine nuances and detail
instruments and voice are presented in a greatly refined spatial envelope and with better spectral balance.
XP-32 – $18,375
The XP-32 is a three-piece modular preamplifier consisting of one control/power supply chassis and two additional gain chassis each containing analog signals of a single channel. The XP-32 generates less noise, crosstalk and distortion while delivering greater dynamic range, gain, output voltage and output current. But it is the sound, not the technical excellence, that truly makes this a breakthrough instrument.




Overall Gain | 9.3dB Balanced |
Remote | yes |
Inputs | 6 |
Outputs | 4 |
Input Impedance | 42k balanced |
Power Consumption | 45 watts |
Number of chassis | 3 |
Dimensions, Each Chassis | 17”W x 12”D x 4”H |
Weight (LBS) | 57.5 |
High-End Phono Stages
XP Phono
High-End Phono Stages
Since 1997 Pass Laboratories has been respected for building some the finest phono stages in the audio industry.
The transition from Aleph Ono, through X-0no and now to the XP-15 and XP-25 represents a sophistication and maturation of both thinking and component evolution.
Single chassis XP-17
Twin chassis XP-27
Adjustable Gain
Resistive and capacitive loading
on all the front panel for easy access.
XP17 uses the new-shielded low noise toroid and input filter module, like the XP-12. The power supply has an extra stage of RC filtering. We have lower radiated and mechanical noise.
The XP17 has an all-new input circuit that is symmetrical and lower in noise and distortion with greater drive capability. Noise is the most prominent part of THD+N in the first section of a phono stage. By lowering noise we get better resolution and dynamics.
Designed with a split EQ network like the XP 25 and XS Phono that is more accurate and can handle greater signal levels.
The secondary stage runs a higher bias output stage with auto bias.
The numerous loading options from the XP-15 are all still available and three gain settings to accommodate low output MC to MM cartridges.
Technical specifications
Awards and Reviews
“Exceptional resolution and dynamics. Stringed instruments sounded divine with richness and fullness, not just details only for the sake of details–the natural timbre of those strings played the prominent role; they were brought to life. Exquisite.” Karl Sigman
“It is as richly colourful, as deeply emotionally communicative and as powerful as the recording that is played. Oh and it has the best bass that I have heard from a phono preamp so far.” Christiaan Punter
AudioArt #350 – Taiwan
An Audiophila STAR component
audiophilia.com
Product of the year – 2017
audiophilia.com
XP-27 – $12,075
The twin chassis XP-27 eclipses the already exceptional performance of the well-reviewed and well-received XP-15, XP-25 & XP-17: delivering enhanced RIAA performance at a fraction of the previous distortion. The new design uses double shielded low noise toroidal transformers in external supply connected via aviation grade circular connectors using silver over oxygen free copper. The power supply is dual mono with two transformers with lower radiated and mechanical noise. Noise is the most prominent part of THD+N at low levels, so by lowering noise we get better resolution and dynamics.The XP-27 input and gain circuitry are similar to that found in the Xs Phono. This means switching and loading is done at higher signal levels, minimizing noise and improving low level performance.

Gain options | 56, 66, 76dB |
Inputs | 2 |
RIAA response | plus/minus .1 dB 20-20 KHz |
Power consumption | 50 watts |
Number of chassis | 2 |
Dimensions, each chassis | 17”W x 12”D x 4”H |
Weight (Lbs) | 45 |
HPA-1 Headphone Amplifier – $3,675
Class A
Announcing the new Headphone Amp from Pass Labs!
Like the XP preamplifiers, the HPA-1 is the result of great attention to detail.
Starting at the power cord, the AC line is first filtered for high frequency noise and then isolated by a special toroidal transformer shielded by mu-metal for lower magnetic noise and shielded for electrostatic noise by a separate Faraday shield, grounded to analog ground. This is followed by fast/soft recovery rectifiers, generous CRC passive filtering and sophisticated discreet DC regulators and then more passive RC filters.
Works with headphones
with impedances of 15 ohms to 600 ohms
Low feedback wide bandwidth discreet design.
Class A
direct coupled Mosfet output stage
Custom low noise Torodial power transformer
with a Farady shield
Discreet regulated power supply for audio circuits.
Technical specifications
Awards and Reviews
“To put it bluntly, Pass Labs HPA-1 is an exceptional, very addictive headamp/preamp combo every aficionado should at least audition once an opportunity strikes.”
” If I did not know that the HPA-1 was transistor-based, I would’ve been fooled: the HPA-1 had the natural warmth and slight fullness that mimic tubes.” ” In my view, headphone listening is about intimacy, and the HPA-1 is nearly perfect in this regard.”
“As far as headphones go, the HPA-1 is a brilliant amp which deserves every bit of praise I’ve thus far heaped on it.”
Headphone Amplifier of the Year – 2016
The Absolute Sound
Best Headphone Amplifier – Best of Awards – 2016
HomeTheaterHiFi
“One Of The Best HPAs In The Audiophile World!”
“The HPA-1 had an effortless quality that made recorded music sound more like the real thing.”
“Pass Labs, one of the most prestigious names in audio, has launched a terrific headphone amplifier”
“in bass clarity and authority and in midrange transparency, the Pass Labs HPA-1 is without peer”
“The Pass HPA-1 is on the top tier of the world’s finest headphone amplifiers”
“This thing sounds so damn good twenty minutes out of the box”
“An amplifier that drives headphones to exceptional performance”
“The best I’ve heard from a headphone amp anywhere near the HPA-1’s price.”
“the Pass Labs HPA-1 is a bona fide muscle amp in the guise of an equal-opportunity preamp with headfi function.”
“Dynamics and authority are two of the best qualities in all listening sessions with the HPA-1, regardless of the headphone. With a great current delivery it also drives any planarmagnetic headphone, with an absolute control.”
AMPLIFIERS
Xs Series
Class A
These are Pass Laboratories ultimate expression of Power Amplifiers the perfect blend of science and visceral emotion.
If there’s a more emotionally satisfying amplifier anywhere, we’re not aware of it.
The successor to our already lavishly praised and well regarded Supersymmetry patent. Every technical effort has been made to assure exceptional specifications, among these:
Separate chassis
for lower electromagnetic noise
Power supplies
with greatly enhanced storage capacitance
Banks of redundantly parallel high speed
and soft recovery rectifiers
Noise filters
with improved high frequency
Larger and quieter transformers
Improved passive decoupling
Lower power standby
Input impedances
of 200 k-ohm balanced with negligible capacitance
Xs 300 mono block – $85,000
The Xs series monoblock power amplifiers represent the reference-quality, state-of-art amplifiers from Pass Laboratories. Through years of “spare no effort” endeavor, they represent the true pinnacle of music reproduction. The Xs 300 delivers 300 watts, employs separate power supply and amplifier chassis’ for lower noise and utilizes higher-power constant-current source. Single-ended bias current not only lowers distortion, but facilitates better control of its harmonic structure, tweaked and optimized through endless listening tests for your musical pleasure.
Technical specifications
Awards
“the Pass Xs preamp and Pass Xs 300 power amplifier—are efforts to provide that absolute sound without compromise in either quality or price. They are new top-of-the-line components that push the state of art in audio to its limits, and they are priced accordingly”
Xs 300 TAS Editors’ Choice Award – 2021
“Solid State Product of the Year”
-Tone Audio- USA
Editor’s choice award 2017
The Absolute Sound
“Solid State Product of the Year”
-Tone Audio- USA
“Best Performance of the Year 2014”
-Audio Art- Taiwan
“Best Products of the year 2013 Award”
-hometheaterhifi.com- USA
“Some might even proclaim them as the very best”
Positive Feedback
“The end result is musically realistic and involving at every level.”
The Absolute Sound
The Absolute Sound’s 2020 Buyers guide
The Absolute Sound
Xs 150 mono block- $65,000
Like the Xs 300, this amplifier was developed through constant and thorough innovation. After years of SIT device experimentation, followed by deployment in Nelson’s First Watt designs, circuit modification captured the unique tube-like sonic footprint of SITs from much higher-output MOSFET devices used in the Xs series. The result is unparalleled, fatigue-free listening enjoyment.
Technical specifications
Awards
Best Performance of the Year 2014”
-Audio Art- Taiwan
“Super Class A Presentation,Super Class A Price Tag!”
Everything Audio Network
“Even straight from the box, they sounded very good”
Dagogo.com
Circuitus Maximus Award 2017
Positive-Feedback
Top o’ the line Brutus Awards 2017
Positive-Feedback
Class A
XA25 stereo – $5,150
The new XA25 offers great sound at slightly lower power, without frills, at a lower price. It embodies new components and innovative circuits coupled with the best elements of the previous generation.
Degeneration, “the other form of feedback”, has been eliminated. The output stage consists of a single pair of 800 watt new generation output transistors operating push-pull Class A. The result is faster, lower distortion, lower noise, higher damping and larger Class A operating envelope into low impedance loudspeakers, all in a simple 3 stage circuit with total of three pair of push-pull gain transistors.









Class | A |
Type | Stereo |
Gain (dB) | 20 |
Inputs | RCA |
Power Output /ch (8 ohm) | 25 |
No Output devices (/ch) | 4 |
Power Consumption (Watts) | 240 |
Standby Power Consumption (Watts) | <1 |
Number of Chassis | 1 |
Unit Dimension (W x D x H) (In.) | 17 x 17.25 x 6 |
Unit Weight (LBS) | 48,5 |
Beyond the inherent sweetness of the XA25’s personality was its ability to transform a listening space into a three-dimensional tableau of images and ambience”
XA25 TAS Editors’ Choice Award – 2021
“As I listened to album after album, I could hear the textures, colors, tones, and harmonics of music in a way that was very moving. The system’s timbre realism with individual instruments and voices was as satisfying with the XA25 as it had been with any amp. All of this added up to enable my system to play music with a wonderful lifelike flow.” Jack Roberts
theaudiobeatnik.com
Recommended Components – 2018
Stereophile
Fidelity HiFi und Musik / Von Cai Brockmann
“Its divine transparency blesses and illuminates every aspect of the music it touches, enhancing the subtlest aspects of tone, texture, microdynamics, space, and atmosphere.”
Stereophile / Herb Reichert
“I thought I would never hear a solid-state amplifier that could create the gorgeous timbres/tonality/color of the finest tube-based amplifiers, yet that’s what you get with the XA25”
hometheaterreview.com / Terry London
“With my audiophile ears standing at full attention I noted that each instrument sounds like it’s in its own “space” on my favorite recordings.”
CNET / Steve Guttenberg
Occasional 2018 Buyers Guide
Part-Time Audiophile
Best of 2018 Award
HomeTheaterReview
Recommended Components – 2019
Stereophile
The Absolute Sound’s 2020 Buyers guide
The Absolute Sound
“I was quite excited when I received notice from Positive Feedback Editor Doc David that there was a Pass Labs XA25 Class A stereo amplifier available for me to write about for Positive Feedback.”
Positive Feedback / Jeff Day
XA30.8 stereo – $7,150
An exceptional stereo power amplifier on many levels — high-biased MOSFETs providing higher-power class A operation, direct-coupled front-end circuitry for exceptionally high stability and larger, more robust heats sinks similar to those of the larger .8 amplifiers. The list goes on, but listening may tell you the XA30.8 represents a value high-point — quite possibly your particular optimal balance between performance and cost.
Technical specifications
Awards and Reviews
HomeTheaterReview – Best of 2016 Award
HomeTheaterReview
“For me, listening to the XA30.8 is not unlike the first time I heard a really great stereo system; it is different, alive, and fantastic”
Writers’ Choice Award, 2015
Positive Feedback
“This would be my first exposure to the grown-up stuff of Pass Labs”
“The Pass Labs XA30.8 excelled at musical flow”
“A pure conduit for music you ask? It truly is, and you must go and listen”
“It has everything you could ever want”
Another stunning review of the XA30.8, available in Tone Audio #78 page 182
Tone Audio
“You can sit for hours enjoying the tube-like, highly detailed musical nature of the XA30.8 with virtually no listening fatigue”
XA60.8 mono block– $14,250
Offering all the sonic benefits of the .8 amplifier line, a pair of XA60.8’s also grace the listener with mono-block performance: dedicated power supplies for each channel, dedicated circuitry for each channel and dedicated chassis’ for each channel offer a cleaner, better defined image and soundstage. Beautiful to the ears and eyes, this model achieves levels of focus and intimacy normally associated with the finest tube amplifiers. The XA60.8’s do all of this while providing greater control and power.
Technical specifications
Awards and Reviews
“Rock-solid dependability, never needing repair”
“There are speakers that need more power and the XA60.8 is the choice”
“So then, you might ask, what is the Pass Labs “family” sound? Different people hear things differently, but for me, it goes something like this: it’s somewhat warm, well-balanced top to bottom, dimensional, and forgiving, all while demonstrating prodigious bass.” John Richardson
“The improvements rendered by the Pass Labs XA60.8s weren’t only in the soundstage; the sound was now, when called for, sweeter, warmer, more delicate—as, for example, with the voices and tenor sax on Getz/Gilberto, an oh, so familiar recording I explored with new interest with the XA60.8s in the system.” Jim Austin
Best of 2017
Parttime Audiophile
Recommended Components – 2018
Stereophile
XA100.8 mono block – $21,000
The middle sibling of the XA.8 series, the XA100.8’s realize a muscular yet highly refined sonic profile. Like all Pass Laboratory’s power amplifiers, they features both single-ended and balanced inputs, Furutech five-way binding posts and a convenient ground terminal for safe subwoofer connection. Improved constant-current sourcing, precise voltage references and current-feedback all represent new benchmarks in state-of-art amplifier design. The result is a larger, more realistic soundstage, sharper transient response and the prized ability to reach concert-hall dynamics and realism without strain.
Technical specifications
Awards and Reviews
“They’re so versatile and rewarding that it would be hard to praise them enough.”
“It would be tragic if you pulled the trigger on another brand/model and then happened to hear what this magnificent beast can do”
“Ignite the imagination and accelerate your heart rate to thousands audiophiles worldwide”
Parttime audiophile Editors Choice
XA160.8 mono block– $28,600
More of just about everything: 72 output power-MOSFETs, higher input impedance, higher capacity power supply and the ability to deliver over 320 watts per channel in class A with greater dampening. The 160.8’s deliver power and finesse in spades. Voices take on shape and depth, piano notes arrive with full acoustic integrity and the rest of the rhythm section is delivered with both powerful attack and holographic sustain. The effortless conveyance of musicality and realism must be heard to be believed.
Technical specifications
Awards and Reviews
“You must audition the XA160.8 I guarantee you will be highly impressed”
Editors’ Choice Award 2017
The Absolute Sound
Best Audio Gear – 2018
The Absolute Sound
XA200.8 mono block – $44,000
Are fabulous-sounding 400-watt-plus per channel class-A peaks attainable without loss of the musical detail or audible meltdown? Yes, through repeated listening tests and continual technical innovation that push performance standards, the XA200.8 achieves what most amplifiers can only dream about. Even for the most demanding, complex musical passages in larger rooms at high sound pressure levels, this model offers headroom to spare.
Technical specifications
Awards and Reviews
“Pass Labs XA200.8 Pure Class A”
“Without hesitation, I could go the rest of my life and never feel the need to upgrade from the Pass XA200.8 amplifiers.
Class AB
X150.8 stereo – $7,150
As the entry-level class A/B stereo power .8 amplifier, the X150.8 features many of the same technical and sonic attributes of its larger brethren. It features 150 watts per channel, 100K ohm input impedance and operates “higher” into Class A than its predecessors. But knowing the ear is not a microphone and the brain is not a tape recorder, we’ve designed this model to bridge the gap between measured performance and outstanding subjective musical experience. Simply put, the X150.8 will compel you to listen to your entire music collection again and again.
Technical specifications
This stereo class A/B model represents a step up in power and performance from the X150.8 and, like all of our products, has been painstakingly designed, tweaked, redesigned and fine-tuned to deliver maximum musical enjoyment. This hard work and creativity results in a greater “look-back” at the original musical performance, conveying additional insight to the artist’s creative intent. Isn’t that what it’s all about?
Technical specifications
Awards and Reviews
“Best of 2015 Awards”
“This generation of Nelson Pass designs is the best that Nelson and his team have created so far.”
“It has been my pleasure to experience the X250.8 as it was another great performer!”
“It’s probably the best sounding power amp I’ve had the pleasure of using in my system up to this time.”
“With the X250.8 there’s detail, but there’s also texture.”
“An amplifier that viscerally connects you to the heart and soul of the musician(s) you are listening to”
“Build quality is top shelf and the design has just enough subtle “audio jewelry” to delight the audiophile crowd”
X260.8 mono block– $14,250
The X260.8 is a refined musical instrument delivering 260 watts into 8 ohms, and combines power and finesse with all the benefits of mono-block performance. Its measured performance – distortion, bandwidth, noise, and resolution is beyond reproach. Like all of the class A/B .8’s, this amplifier has some class A bias, rewarding its listeners with a whole new zenith of sound quality.
Technical specifications
X350.8 stereo – $14,900
At 350 watts per channel class A/B, the X350.8 is the largest and most powerful stereo power amplifier of Pass Labs line-up. Because we care more about how holistic design affects the musical experience and relatively less about how parts affect specifications, you can expect superb and accurate representation of the recording performance and venue, as well as the distinctive layering of instruments captured faithfully.
Technical specifications
Awards and Reviews
“This is a high-powered, audiophile amp that delivers the desired sound”
“A superb example of the Pass Labs commitment to trickle down product development”
Positive Feedback Writers Choice Award
X600.8 mono block – $28,600
The X600.8 monoblock amplifiers deliver 600 watts into 8 ohms. Even more impressive they effortlessly drive the most demanding loudspeakers to musical nirvana, be the performance full scale orchestra, high-decibel rock band or string quartet. Exhaustive listening tests, not myopic focus on specifications have informed the development of this and the rest of the Pass Labs product offering, and you can hear it.
Technical specifications
Awards and Reviews
“Solid build quality”
Best of 2017
Parttime Audiophile
Audiophiles, serious Audiophiles, have not considered an integrated amplifer as worthy product for 30+ years. Pass Labs has changed this paradigm, forever!
Like the INT-60, the INT-250 utilizes the synergies developed in the .8 series power amplifiers. Unlike the INT-60, however, it brings 250 watts per channel of listening pleasure. With higher power MOSFETs and more of them, the INT-250 drives large, demanding and relatively inefficient loudspeakers at higher volumes without batting an eyelash, singing beautifully. Just incredible music from one component.
Seven years in the making, the Point 8 Series demonstrates our belief that the best products must be carefully adjusted until their components operate in harmony.
Low distortion
Additional loudspeaker control
at ordinary listening levels
Higher power MOSFETs
to increase the amplifiers’ Class-A operation
Enhanced performance and reliability
Directly coupled front ends
to maximize each model‘s output stage performance
Technical specifications
Awards and Reviews
Editors Choice Award – 2017
The Absolute Sound
Best Performance of the year – 2017
Audio Art – Taiwan
Integrated Amplifier of the Year – 2016
The Absolute Sound
“The INT-250 also throws its prodigious weight around in the most unexpected and tender ways.”
Brutus Award
Postive Feedback
INT-60 – $9,450
This integrated amplifier sets a new benchmark in significantly narrowing any perceived performance gap between separate components and integrated amplifiers. Advanced technologies and real-world testing combine to create the INT-60 which presents 60 glorious watts per channel into 8 ohms, and doesn’t leave class A until 30 watts thanks to its high-bias operation. This larger class A operating envelope brings lower distortion and greater loudspeaker control, delivering higher quality musical fidelity for your enjoyment.
Technical specifications
Awards and Reviews
So what does the INT-60 sound like? I’m sure this is too simplistic, but it sounds like music.
“Distilling it all down, it’s an amplifier that makes me happy because it gets me more involved and closer to the musical experience.”
“The INT-60’s dominant trait was to suck me in and glue me to my seat as it continued to reproduce music with so much low-key flavor, natural color, and more-ishness that I could never play just one record and go to bed early. ”
“Writers’ Choice Award 2015”
“I strongly recommend that you check out this remarkable audio achievement.”
“Technical progress and music fun”
Constitutes the heart of the integrated amplifier
Writers’ Choice Award, 2015
“if you want to hear beautiful music produced by an integrated amplifier that is built to last a life time and is one handsome-looking beast without constantly messing with your system, the Pass Labs INT-60 integrated amplifier is for you.”
“The INT-60, indeed, is one of the best sounding integrated preamp/amplifiers I have ever reviewed. It is tough to better the INT-60 with separates in this price range. Even if you spend a bit more, you probably will not top it. Incredible detail, width and depth in the expansive stereo image, plus quick bass response.” John Gatski
Writers Choice Awards 2017
Review from Poland:
Polish review with lots of pictures
INT-25 $7,600
At Pass Labs we build Fet amplifiers with excessive output stages, huge heat sinks and massive power supplies. We use the highest quality components in simple linear topologies, assembled and tested with care and subtlety. They measure well, sound great, and are reliable. Twenty plus years of ongoing innovation have kept the X and XA amplifiers at the forefront of high-end audio.
The INT-25 embodies all this and less. A smaller stereo Class A amplifier at a lower price, it takes advantage of the lower power requirements to have simpler single-ended circuitry and fewer parts in the signal path. This also allows elimination of degeneration, “that other negative feedback” in all stages.
Simpler and fewer gain stages improves speed and stability. Lower voltages means the ability to run gain devices at higher bias currents, more deeply into Class A. Newer power Fet technology replaces banks of parallel small transistors with a single pair of industrial devices, each having a 700 watt / 40 amp rating. With no current-hogging issues and a new constant-current bias circuit to compensate for temperature drift, they connect directly to the loudspeaker without ballast resistors for lowest possible distortion and highest damping factor. No degeneration also increases the efficiency and Class A operating current, allowing greater Class A operation into low impedance and reactive loads.
The simple front end circuit uses two pairs of our favorite NOS complementary Fets in common-source mode in a current feedback (CFA) configuration.
The preamp section is a simplified single-ended version of the one used in the INT-60 and INT-250 with three line level inputs and no line level output.
Everything done in the signal chain from the microphone to the loudspeaker, forever leaves an indelible mark on the music. The XA25 amplifier section is direct coupled requiring no DC servos or frequency compensation, neither adding too or subtracting from the experience.
As with all Pass amplifiers, the technology and construction are strictly in the service of the listening experience. The INT-25 measures superbly, but its subjective qualities are most special. In an industry where products with great specs are often found to be dry and boring, this amplifier breathes new life into the music.
Technical specifications

J2 Power Amplifier – $4,000
The J2 is a stereo power amplifier rated at 25 watts per channel. It has a two-stage circuit that operates in pure single-ended Class A mode, with signal JFET devices forming the input stage and power JFET devices for the output stage.
JFET transistors have long been recognized as having the highest audio quality of any transistor; the input devices of the J2 are known through the industry as the standard for low noise and linearity, and are found on the inputs of the finest phono stages, line level preamplifiers, and power amplifiers.
But for over 30 years robust power JFETs have not been widely available since the short-lived efforts of Sony and Yamaha. In the last few months, advances in Silicon Carbide (SiC) technology have resulted in new power JFET transistors with high voltage, current, and power capabilities – as high as 1200 volts, 30 amps, and 273 watts.
Created by SemiSouth Corporation of Mississippi, these robust new JFETs are designed for very fast high power switching in solar power and electric car applications. However, they also have a very low distortion characteristic that makes them superb for use in linear amplifiers. In apples-to-apples comparisons with comparable MOSFET type power transistors, they can achieve 10 to 20 dB improvements in distortion performance.
For over 10 years First Watt has been pushing the design envelope with simple high performance Class A amplifier circuits, and when a better transistor like this comes along, it can mean getting the same distortion performance with a lot less feedback, or lower distortion with the same amount of feedback. The J2 does amplifier does both,and that helps make it a better sounding amplifier than the best of its predecessors.
With a device that behaves a little like a tube, it is natural to consider popular tube amplifier design topologies. Single-Ended Class A tube amplifiers are not very powerful, and their measurement numbers are not exceptional, but there is no arguing that they have strong musical appeal to much of the audiophile population. The J2 amplifier uses a classic JFET differential input stage followed by a single power JFET transistor. This power JFET is biased by another JFET in what is known in tube circles as a “mu follower”.
Here is a slightly simplified schematic of the J2 circuit. It could be a classic tube amp, except that the P channel input JFETs would have to be fabricated from anti-matter. The single-ended Class A output stage is “second harmonic” in character, and it uses about half the feedback of a comparable MOSFET circuit but with half the distortion and twice the bandwidth.
The J2 power amplifier is simple, clean, and measures astonishingly well. It achieves a sound which is warm and relaxed, combining precision and detail without sterility. With a pair of sensibly efficient loudspeakers, it will give you a toe-tapping experience that other solid state amplifiers do not. The design is extremely reliable and will never need adjustment.
F8 Power Amplifier – $4,000
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.
It is similar to the J2 amplifier, but has only one front end transistor instead of six, operated as a current feedback amplifier (CFA) as opposed to the J2’s voltage feedback (VFA) differential input. This front end is more consistent with the single-ended approach to amplifier design and yields a purer second harmonic character, less distortion with lower negative feedback, greater bandwidth and higher damping factor.
F7 Power Amplifier – $3,000
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.
The F7 is now in production.
Here is a link to the first of many reviews: F7 at 6moons
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