F1J Power Amplifier Update. Unlike many companies and I'm sure you can name some First Watt is grateful to the early adopters who took a leap of faith and bought either an F1 or F2 amplifier. This page is about the F1J there is another about the F2J.
Most of what you might want to know about the F1J amplifier can be found in the documentation of the F1 power amplifier. I recommend downloading the owner manual for the F1 and the articles on current source amplification. The F1J is an update to the F1 where the two gain Mosfet transistors have been replaced by new state-of-the-art power Jfet devices.
In addition, there have been changes to several resistor values and removal of the input zener protection diodes. As with the F1, the simplified circuit of the F1J looks like this:. The reason for bothering with this modification is very simple — better performance from faster, lower distortion parts.
Here is a distortion vs power comparison between the original F1 and the F1J in the low to midband range where you see the newer parts have less than half the distortion:. The difference is even more dramatic when we compare the distortion at 20 KHz:.
We can also see this difference at a fixed wattage vs frequency:. The F1 has always favored balanced input operation over single-ended input, but the characteristics of the Jfets help to narrow the gap between the two.
As a result the improvement is even more dramatic between the F1 and F1J when operated single-ended:. Noting the improved performance for distortion at high frequencies, it is not surprising that the F1J also has more extended bandwidth as seen below:. You may notice that the F1J also has approximately 1. This is because the Jfets have a higher transconductance figure that the original Mosfets. There is another factor as well, which is that the F1J has a lower input impedance than the F1- approximately 30 Kohm balanced and 15 Kohm single-ended.
The modifications that help achieve this bandwidth take advantage of lower impedances, so the F1J is recommended for use with preamps with ordinary to low output resistance — tube preamps without cathode followers will work but will not reap as much benefit at high frequencies. This caveat aside, the F1J delivers a dramatic improvement in current-source amplification. I have often ventured the opinion that improvements in measured performance in simple Class A circuits particularly with no feedback usually have the best correlation between what you measure and what you hear, and the F1J bears this out.
I think it sounds about twice as good, and I feel certain that you will experience the same remarkable improvements.
The period for factories updates has elapsed, so at this time you are on your own. Here is the schematic and some instructions for the DIYers. Refer to the original documentation for original schematics and locations of components on the pc boards. F1J Power Amplifier Update Unlike many companies and I'm sure you can name some First Watt is grateful to the early adopters who took a leap of faith and bought either an F1 or F2 amplifier.
As with the F1, the simplified circuit of the F1J looks like this: The reason for bothering with this modification is very simple — better performance from faster, lower distortion parts. Here is a distortion vs power comparison between the original F1 and the F1J in the low to midband range where you see the newer parts have less than half the distortion: The difference is even more dramatic when we compare the distortion at 20 KHz: We can also see this difference at a fixed wattage vs frequency: The F1 has always favored balanced input operation over single-ended input, but the characteristics of the Jfets help to narrow the gap between the two.
As a result the improvement is even more dramatic between the F1 and F1J when operated single-ended: Noting the improved performance for distortion at high frequencies, it is not surprising that the F1J also has more extended bandwidth as seen below: You may notice that the F1J also has approximately 1.In case you are unfamiliar with the name, Johnson was a chief designer for Lockheed Martin who was the brains behind such legendary aircraft as the U2 and SR Blackbird reconnaissance aircraft.
This place was so secret that supposedly the government refused to admit that it existed, and the tinfoil hat crowd believes to this day that alien technology is housed and tested there. Most folks here are familiar with Mr. If Pass Labs is more akin to the major company e. The pilots who fly such craft consider themselves a special breed indeed, much like those oddball audiophiles who lust after the rarefied First Watt amplifiers.
First Watt products tend to fly under the radar as opposed to above it, like the U2as they are small, unassuming, low-power solid state class A designs. The most powerful one still in production, the J2, puts out a parsimonious 25 watts into eight-ohm loads. All First Watt amps look alike, thanks to the simple casework which Nelson apparently got in a one-time batch deal. Each stereo First Watt amp is also easily recognized by its pair of blue LEDs on the front panel, which looks out upon a dark room like a pair of tiny, menacing eyes.
In his First Watt offerings, Mr. Pass is all about simplicity and elegance of design. Simpler designs sound better — within certain constraints, he tells me. To the end-user, the real question is whether one can get by on 25 watts or less.
Of course, the answer to this question depends on any number of variables, though common audiophile logic and marketing combine to tell us that low power is a bad idea in most cases.
My own experience tends to argue otherwise. I have an old Kenwood integrated amp from the golden audio days of the s that is equipped with power output meters. Remember those and how hypnotically cool they were? Mine are calibrated in instantaneous watts of output power.
First Watt SIT-3 Amplifier Review
When I hooked the amp up to a pair of speakers of normal impedance and sensitivity of, say high 80s or so and watched the meters dance, I was somewhat astounded to see that they never went above one watt of power per channel at the normal volumes at which I listen.
I got to thinking … Why buy a watt per channel amp when I was only using that first watt? Before receiving this amp for review, I received some correspondence that described in fairly simple terms its unique design. The SIT is a special and unique output device, as it was designed specifically for audio reproduction to capitalize on its characteristic triode-like behavior.
The actual design of the amplifier is unique and somewhat interesting. Voltage followers are interesting in that they provide large current gain with a voltage gain of unity. In other words, a classic voltage follower sports a very low output impedance, thus effectively providing whatever current is required to drive the downstream load.Amp Camp Amp (ACA) Nelson Pass Class A amplifier clone review and teardown.
Of course, voltage is important to proper amplifier operation as well, so that type of gain is provided by an autotransformer at the input, buffered by a pair of JFETs, which gives 11 dB of voltage gain per channel. Sonic advantages you ask? These factors together point toward a more accessible design that should enjoy a greater audience of audio enthusiasts by curbing some of the limitations of the earlier SIT designs while still providing a unique listening experience based around the SIT device itself.
The icing on the cake? Either way, it sounded decent out of the box and got continually better over the next couple of weeks of near constant use. To best put the sound of the SIT-3 in context, it might be good to re-visit what I remember about listening to its older sibling, the SIT-1, which I spent time with as part of a review of several First Watt amps published a couple of years ago.
What I best recall about the SIT-1 which actually came as a set of monoblock amps was its smooth, warm, and dimensional character. There was a wonderful sense of layering to the sound, and the notes had real body and textural heft to them.The J2 is a stereo power amplifier rated at 25 watts per channel. 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 volts, 30 amps, and 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. 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.
Press and Reviews 6moons by Srajan Ebaen Oct. Ultra Audio by Vade Forrester Nov. Stereophile by Herb Reichert Sep. Manuals and Guides. Specs Technical Features.
Distortion 1 watt. Related Products. Add to Cart. Customers Also Viewed. Choose Options. Get the latest News Email Address.Years ago, a reviewer friend said, "Herb, I don't review loudspeakers. You don't review amplifiers, either? Like I said, my speakers are easy to drive. Except for the fact that this speaker's impedance remained below 3 ohms for almost seven full octaves, from 55Hz to 6kHz!
At 3kHz, it was only 1. Easy to drive? I'm telling you about my friend's reference speakers because the amp I'm about to describe might not sound too authoritative while driving them.
Because when the SIT-3's dancing partner is a compatible pair of speakers, it's one of the two or three finest-sounding amplifiers I've heard anywhere, at any price. Which is why I think the most important question an audio reviewer must explore is: What constitutes a compatible loudspeaker for the amplifier being reviewed?
According to the abstract of inventor Jun-ichi Nishizawa's patent, as quoted on First Watt's website, "SIT's drain-current to drain-voltage characteristic simulates the anode-current to anode-voltage characteristic of the triode vacuum tube very closely. The first of these is Digital Do Main in Japan, which has produced two audio amplifiers based on newer versions of original Yamaha Silicon parts.
The Source pin is grounded. The amplification with Common Source operation is both voltage and current, and the phase inversion is corrected by reversing the output terminals. It has no phase inversion. Their voltage and current love-dance was such a joy to behold that I had to look up John Atkinson's measurements of the P3ESR's electrical impedance and phase, just to see what type of load was making the SIT-3 so happy.
After trying every high- and low-impedance speaker in my Bed-Stuy bunker, it was clear that the SIT-3 was most comfortable with speaker loads above 4 ohms and below 8 ohms. I played a wide variety of big and small music through the SIT-3 and P3ESR combination, but I want to tell you about two special recordings: one was simple and stunning, the other was big and s p a c i o u s. I've never heard a band with an accordion that I didn't like.
Nor have I ever heard a record by accordionist and experimental electronic artist Pauline Oliveros I didn't want to play over and over. I like her because her musical theory advocates "deep listening" and "sonic awareness," as well as learning to listen "alertly and constantly" aka "always be listening," footnote 2. I aspire to blur the line between our experience of music and the quotidian. I felt I could measure the added reverb. I thought I could feel the air moving in and out of her instrument.
Footnote 1: For a detailed explanation of what Nelson Pass means by "control of the amplitude and phase of the second harmonic content," see my "Gramophone Dreams" elsewhere in this issue. Scarecrow Press, The answer to that question will be found in the April issue of Stereophile. John Atkinson Editor, Stereophile Log in or register to post comments How is it possible that an amplifier in which Submitted by Ortofan on January 22, - pm Wouldn't an amp that adds as little harmonic distortion as possible, such as the Benchmark AHB-2, do a far better job of preserving the geometry of the original harmonic relationships?
When Herb writes " I felt I could measure the added reverb. I wondered why he didn't include an actual measurement to back up this "feeling". Next his thought that he could "feel the air moving in and out of her instrument" sounds like pure unadulterated mystical hyperbole. Less hyper-hyperbola please.
That type of description is WHY we read these publications and websites. Sometimes light is shed on the subjective response by John A's fact checking measurements but not all of it. So we take these written feelings and if they sync with how you like to feel and hear recorded music you add said equipment to your list of pieces to audition.
If you want a measurement to back up every comment, you're wasting your time reading audio reviewers. I'm sure there are people who feel that the more expensive olive oil is a waste of money" as "taste" is a subective thing.
Ditto with more expensive wines. According to johnnythunder readers of the mags he quoted only want how a product "feels and sounds With that as the ultimate criteria for reading those mags why do the measurements sometimes appear at the end of the reviews?LOG IN.
Hi everyone, I'm looking for a good preamp for my First Watt F7 amp. F7 has input impedance 10K Ohms, gain of 14 dB. I once had a First Watt M2 amp that I employed through a simple tubed pre - I forget what manufacturer.
It sounded beautiful. After that I always put a tubed pre with my Pass Labs amps, too. Linear Tube Audio MZ2. Sounds great with it, output impedance 50 ohms. Stay away from the Schiit Saga's as they are only unity gain. Cheers George. Rowland Capri was recommended to me by Pass dealer and it is a great combination See bellow the answer of Mr.
Pass: The F7 has a lower input impedance than most, at 10K, and a little less gain than most. Preamps that would have difficulty would be ones where the output impedance is greater than ohms or so, or tube preamps that cannot driver 10 Kohm, or which have no voltage gain. As it is, I routinely use the the F7 with a B1 which has no voltage gain, but my sources have 2V or more. I am starting questioning do I really need a dedicated preamp to improve the sound.
I guess I'm opening the can of warm "Do you and when you need a preamp". Good luck! Log in to respond. More to discover Is anyone aware of a 2 channel preamp Music First Audio Classic. Eastern Electric Minimax Phono. Output impedance: Ohms. And SE preamp I assume?In hindsight, you would surmise that First Watt was rather lucky. With only about SITs remaining in stock enough to make amplifiersNelson wanted to release one more SIT-based design that was quite different in his view.
I think it is the most interesting of the First Watt SIT amplifiers, and for about people it will be the best. The amplifier requires about one hour of operation to reach its maximum operating temperature. Nelson does not see a reason to run the amplifier all the time, but gives you the green light to do so. I found the SIT-3 to improve sonically after about a tominute warmup.
And the level of improvement was not subtle. Hence, it would be prudent to turn it off during long idle periods. The SIT-3 consistently blurred the line between solid-state and tube amplification. Its tonal focus was on the midrange. And as far as harmonic textures go, while no one would mistake it for a tube amp, its presentation was slightly liquid, warm, and grain-free—welcome traits that enhance long-term listenability.
Designer Mike Moffat likes to play sonic horseshoes; his goal is to approach the sound of the big boys at a fraction of the cost. But when it comes to grainless pristine textures, if the SIT-3 is a 10, the Vidar is only a 6. Then there is the perception of textural density. The tendency of solid-state designs is to thin out textural weight.
The complexity of various timbres is typically watered down, if you will, thereby short-changing the density of the real thing. In general, tonal richness is captured much more realistically by tube designs, though as we all know they sometimes err toward excessive lushness.
In fact, its textural flavor is very much dependent on that of the associated preamp. Roger Sanders refers to the Isis as a fine little speaker. Yes, I know, the SIT-3 is way underpowered for this application but I was curious about its midrange performance in this context.
It was worth the effort, as I was rewarded with detailed, nuanced mids and excellent image focus, though as expected the bass range was severely constrained. Enter the Quad ESL The SIT-3 was much happier with the Quads and was able to generate a believable tonal balance within an expansive soundstage.
As with the F7, the SIT-3 is easy to embrace musically. It is clearly a remarkable, deliciously organic-sounding low-power amplifier, a contender for best in class, and is surely destined to become a classic. Power output: 18Wpc into 8 ohms; 30Wpc into 4 ohms Frequency response: G Auburn, CA firstwatt.Stereophile measured the gain of the SIT-3 as being For an amp having that gain to provide an output of 30 watts into 4 ohms, which corresponds to Therefore it appears likely that for MM phono cartridges the Brooklyn Bridge provides gain that is similar to what Stereophile measured for the Brooklyn DAC, namely That corresponds to a voltage multiplication of x.
A gain of The corresponding power supplied by the amp when the cartridge is supplying its rated output is 0.
The peaks of various recordings can of course be either somewhat greater than or somewhat less than the standard LP test conditions.
If neither of those things is done, what is called for is providing additional gain between the Brooklyn Bridge and the amp.
First Watt SIT-3 Stereo Power Amplifier
The simple one-tube line stage I linked to earlier provides a gain of 22 db. Do you believe the S. Either can be driven by low power SET amplifiers. LOG IN. The Mytek serves as the phono stage 69dB gain for MM? I understand that the SIT-3 is only I like most everything about the system except for the fact that I have the Mytek maxed out volume-wise many days.
Certain LPs are cut quieter, and I wish I had more power.
First Watt SIT-3 Amplifier Review
There are times streaming where the Maggies aren't getting to their sweet spot. I realize the Maggies are a lower sensitivity speaker. What should I look for in a preamp to fully drive the SIT-3? Eventually, I'd like to replace the phono stage instead of relying on the Brooklyn. Otherwise, I'm eyeing the Modwright PH 9. I'm looking for a warm sound, not analytical but engaging. Any help is greatly appreciated.
I'm a working musician with a basic understanding of related electronics but little experience in this world. You certainly need more power watts to drive the. The SIT-3 is what - 15 watts? Adding a different preamp ain't going to change the equation! Either sell the. The Mytech is fine connected to any amp - no need for a separate preamp! The assessment of roberjerman is on the mark.
T-3 and purchase a more suitable speaker for it higher sensitivity with an easier to drive speaker impedance load. This amplifier delivers less than 20 watts into a 4 ohm load. The maggies 83 db sensitivity need more than this to perform at their best. Yet if matched with an appropriate speaker according to owner feedback the S. I believe that your amplifier is the better of the two products and offers more sonic performance potential upside ultimately.
I readily acknowledge that this is simply my humble opinion. With the appropriate speakers, the SIT3 is sublime. Everything said by the others is right on.