by John Richardson
A Clutch of Amplifiers
Let’s start this review with a little chat about First Watt and its founder, Nelson Pass.
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. For many years, he was also the head designer for these outfits, coming up with some of the legendary solid state amplifier designs of all time. Mr. Pass is also a huge presence in the DIY audio community, where he is affectionately known as “Papa.” In fact, it’s the DIY aspect that got Nelson’s spin-off company First Watt going some years back. I see First Watt as something of a quirky niche brand, one that will appeal to certain hard-core audio hobbyists, but probably not as much to the general audio community. No worries, as that’s why Pass Labs exists and thrives parallel to First Watt.
I think First Watt is especially cool because it’s the venue in which Mr. Pass gets to really stretch the limits of his artistic license without pressure. In other words, he doesn’t have to supply products that fulfill a marketing department’s TAM analysis, so he can (at least in theory) “do things” as he pleases. To this end, his choice has been to work with low-powered class A solid-state designs of disarmingly simple character. In other words: “keep output devices, regulation devices — and everything else — to a minimum”. Why? Because, Mr Pass says, simple circuits tend to sound better than complicated ones,” especially within the limitation of low power output. You might say that the electrons simply have to noodle through fewer “chutes and ladders” to get the ultimate job done.
Also, since First Watt is truly a low volume company, Nelson Pass has a much stronger presence in the entire operation. In fact, he not only designs the amps, he (up until very recently) actually built them all in his own workshop! As announced on the First Watt website, as of spring 2016, all assembly has been transferred to the good people over at Pass Labs, Nelson’s more commercial endeavor which leaves Papa Pass free to experiment with some pretty esoteric electronic devices that probably couldn’t be used by a larger company with bigger production goals. For example, the J2 amplifier on review here (as well as several other designs), utilizes high power JFET output devices from the now-defunct SemiSouth company. According to Mr. Pass, these output JFETs are exceptionally robust, operate at crazy-low distortion, and have a gain curve that mimics certain power pentode tubes. Focusing on this last point, the devices can therefore be employed in single-ended circuit configurations similar to those used by some of the most famous vacuum tube designs, thus allowing what distortion there is to be mainly of the “easy on the ears” second-order harmonic variety. In other words, a solid state output device is more or less employed as a vacuum tube because it essentially behaves like one. Should we be worried that these JFETs are no longer in production? Not really, according to Mr. Pass, because he bought up enough of them to keep steady production, and future service of the amplifier models that use them, going well into the future.
Before I get into the specifics of the three amplifier models on review here, let’s get a few other things out-of-the-way. First off, the First Watt amplifiers can be affordable, but aren’t exactly cheap. For example, the 25 watt per channel J2 I have here sells new for $4000, while the 10 watt per channel SIT-1 monoblocks go for $10,000 per pair. As a point of comparison, the Pass Labs X250.8 powerhouse that I reviewed a year or so ago can be had for less than a stereo pair of the SIT-1 monoblocks. Secondly, compared to many amplifiers of comparable (or often lesser) price, the First Watt offerings aren’t exactly sexy looking. They’re not at all flashy, but rather plain and business-like. I don’t have a problem with this approach personally, because they still exude solid build quality, and the real value is what’s under the hood, not to mention the fact that the buyer is paying Nelson Pass himself for his personal attention to design and constant testing. Keep in mind that these amps represent a low volume, highly personalized effort on the part of the designer/developer.
And now, the amplifiers….
On hand for my listening (and your reading) enjoyment are three variations of the First Watt amplifier. First up is the more traditional 25 watt per channel stereo J2, which is a single-ended design employing JFET output devices and zero feedback, which retails for a cool $4000. Much has already been written about this amplifier (Scot has some notes about this amp over here), so I won’t belabor it too much.
Next is a pair of very refined $10,000 per pair monoblock amplifiers, the SIT-1 duo, which put out 10 watts per channel into both 8 and 4 ohm loads. These SIT-1s are even more esoteric than the J2 for a couple of reasons. First, the amps use a seriously rare and unusual type of output device called a Static Induction Transistor, also sourced from SemiSouth. These devices were not originally designed for audio use, but they seemed to have certain desirable capabilities allowing them to perform in ways normal audio transistors don’t. They’re robust and powerful enough to serve as the only gain device in the amplifier circuit, meaning that said circuit can be crazy simple. That is, the audio input signal goes straight to the gate of the device, which then outputs via its drain a proportionally amplified signal directly to the speaker. Secondly, since the output signal is satisfactory to drive loudspeakers, there’s no need for an output transformer, degeneration, or feedback of any sort, so none is used, thus providing fewer layers of electronic woolliness. We’re talking seriously straightforward here, folks, so we ought to expect some pretty pure, unadulterated sound coming from these amps. The esoteric nature of the amps is reflected in their asking price of $10,000 for the pair.
Our final candidate is Nelson Pass’ most recent design, the stereo F7, which offers up 20 watts per side into both 4 and 8 ohm loads. Papa Pass says this design is the simplest First Watt two-channel amp of them all, with a two-stage output whose final output stage consists of a single pair of MOSFETs. It retails for $3000, making it also the least expensive of the First Watt amplifier offerings. The F7 employs both negative voltage and positive current feedback, which reportedly helps it to better adjust to variable and reactive speaker loads, creating a circuit that behaves like a well-choreographed dance between speaker and amp.
On the surface, all three of these amps look pretty much the same, as they are all constructed using the same chassis, heat sinks, transformer, and casework to keep things simple and assembly costs down. The SIT-1 amps are visually set apart from their brethren via a circular analog meter on each front panel, which allows the user to keep track of the bias of the output device (more on this later).
My goal was to examine the performance of each of the aforementioned amplifiers driving a range of three different loudspeakers that I had on hand. I intentionally wanted to find out how the amplifiers would behave driving speakers of differing sizes and efficiencies, so the following speakers were utilized:
- Zu Audio Druid Mk. V; 101 db efficient
- Fritzspeakers Carbon 7 SE; 89 db efficient
- ATC SCM 19 version 2; 84 db efficient
Therefore, I had a 3×3 grid of speakers and amps to evaluate, leading to nine possible pairings. Even though I’ve spent some amount of time listening to most of these pairings across a wide range of music genres, for the sake of efficient evaluation, three music selections were chosen for this review:
- Alwyn, Sinfonietta for Strings (LP, Lyrita, digitally archived)
- Mozart, Laudate Dominum, from Like as A Hart: Psalms and Spiritual Songs (CD, Chesky)
- Natalie Merchant, “River”, from Tigerlily (CD, Elektra)
Focusing on system setup, analog signal was fed from an Antelope Audio Zodiac DAC directly to the amp under evaluation; volume was controlled directly from the variable output on the DAC. The high-gain XLR outputs on the DAC were used in order to maximize gain into the amplifier. Since only the First Watt J2 has balanced XLR inputs, XLR to RCA adaptors were used on the DAC end along with a pair of RCA terminated TelWire analog interconnects to feed signal from the DAC to each amplifier.
On with the show! Evaluating the amplifiers in reverse order of their introduction…
First Watt F7
All in all, the F7 and the Zu Druids offer up an honest, uncolored, and energetically dynamic reproduction of well-recorded music. No worries about power here either, as I was able to crank the tunes up to levels that normally make me uncomfortable, yet still enjoy them immensely. Dangerous stuff, indeed.
Moving on to the F7 driving the less-efficient Fritspeakers Carbon 7 SE monitors, I continued to get excellent and engaging sound. To compensate for the difference in speaker sensitivity, I had to set the volume control on the DAC to about the 1 o’clock position to get comparable volume to what was provided by the Zu Druids when set to 11 o’clock. Even so, I still felt like I had sufficient headroom, as dynamics remained impressive. Massed string crescendos were plenty satisfying, making the Carbon 7s sound larger than they actually are. Even though the F7/Carbon 7 combo didn’t seem as lithe off the line as the F7/Druid coupling, I felt that I preferred the more fleshed out tonal perspective with the Fritz speakers. Midrange notes boasted a silky, glowing warmth that drew me in to the listening session and left me chained to my chair. Further, the upper register of the violins was silky and open, but perhaps not quite as extended as with the Zu speakers.
One uncanny characteristic of the Carbon 7s that the F7 brought out was their ability to disappear into the soundstage. In both the Mozart and Natalie Merchant pieces, the speakers seemed to disappear altogether, throwing a huge soundstage that extended quite nicely behind them. I had the Zu Druids set up a few feet behind the Carbon 7s, and at times, I was hoodwinked into thinking that the sound was coming from the Zu speakers! Also, in both pieces, the female voices exhibited decent extension, but with a silky sheen that added a degree of body that was forgiving and easy on the ears, yet not quite as aggressive as I heard with the F7 driving the Druids.
For me, the First Watt F7/ Fritz Carbon 7 SE coupling hit a particular sweet spot in my own listening enjoyment, expertly balancing power, dynamics, and engaging tonal perspective.
Finally, the last pairing for the F7 was with the somewhat inefficient (84 dB) ATC SCM19 (Version 2) studio monitors. Even though these speakers present an easy load for the amplifier, they do require some power and gain to really get up and go. My initial feeling was that if the F7 were to fall on its face, it would be with this pairing. I hooked the SCM19s up and almost gingerly turned the volume knob. Surprise surprise — I only had to go a tad bit further than I did with the Carbon 7s to get fulsome, full-bodied (and loud enough) sound. Maybe a bit closer to the 2 o’clock position, but still with some room to negotiate upward if needed. That is, the notoriously inefficient ATC speakers just lit up, sounding as ballsy and dynamic as ever. Of course, such a setup may not be sufficient for headbangers, but these folks probably won’t be in the market for a First Watt amp anyway. If it’s all about touch and finesse, then this combo sure as heck had it.
The presentation of the Alwyn Sinfonietta was absolutely gorgeous. The string sonorities were captured with aplomb, especially in the lower registers, where I could hear the real power of bow against string, and the resulting vibrations flowing outward into the recording venue. Again, I had no trouble placing myself mid-distance in the concert hall and taking in the performance as if it were a live event. One thing that helped suspend disbelief was the intrinsic resolution and clarity of the ATC monitors, which were not in any way diminished by the F7. At the upper end of the spectrum, violins were sweet and extended, almost euphonic, and never over the top in treble energy. Again, this was, from a purely tonal perspective, a match made in heaven. The soundscape was also effectively rendered, though maybe not quite as deep as with the Carbon 7 SEs in the mix.
My feelings about the F7/SCM 19 combination track with the F7 driving the Fritz Carbon 7 SE monitors. Perhaps the female voice was not quite as round and smooth, but the tradeoff was slightly more resolution, as to be expected from the ATC monitors with their recording studio heritage. Regarding the reproduction of Natalie Merchant’s vocals on “River,” I’d have to say that the purity of tone was somewhere between what I heard with the Carbon 7 SE and the Zu Druid. In other words, a lovely unadulterated treble tone with a sprinkling of smooth satin thrown in for good measure.
Let’s say it just doesn’t get much more enjoyable than this.
First Watt SIT-1
The First Watt SIT-1 monoblock amps are definitely some of the most fun amplification devices I’ve had my hands on in some time. Why? Because you can tune them to sound their best when using any pair of speakers you choose to drive with them. This feat is accomplished using the front panel knob to adjust their voltage/current bias in order to squeeze that last bit of performance out when matching the amps to a particular pair of speakers. I began (as I’d advise any new user to do) by setting the bias at the dead center position on the front panel meter to get an initial feel for the sound of the amps. Of course, when you do get to messing around with the bias, the rules are pretty simple. Generally speaking, stay in the green region of the dial, but otherwise set the bias to where you think it sounds best. That’s it. Here’s the deal: turn the biasing knob left, and you get a more laid back, palpable presentation of the music; turn it right, you get more bass control and better power handling. Think of it as single-ended triode vs. ultralinear, and everything in between.
My initial impressions were that the SIT-1 shares a lot of the characteristics that make the F7 (and J2) so lovable, namely, a wonderful sense of harmonic accuracy, great microdynamic touch, and a serious sense of transparent immediacy. In fact, I’d say the SIT-1 can offer these things up, especially in the warmth, purity, and palpability areas, in a little more generous helping than either of the other two amps, while also giving an uncanny sense of space around performers in the soundstage. Here, the stereo imaging was exceptionally sure-footed, with no wandering or wavering of individual images or their edges. That effect was almost eerie and really made me sit up and take notice.
Of course, the tradeoff is power. The SIT-1 pair offers up only 10 watts per side, as opposed to 20 watts per channel for the stereo F7. If I expected the F7 to have issues driving any of my speakers, I’d expect even more problems when using the SIT-1. The F7 surprised me in its ability to drive inefficient speakers well; would the SIT-1 be able to follow suit?
I didn’t expect any problems driving the Zu Druids, and none developed. In fact, I found this particular pairing to be exceptionally dandy, to the point of using the SIT-1s as the primary amplification source for my review of the Druids [editor’s note: coming soon]. I had found that the Zu speakers could be a bit overly energetic, perhaps a little overenthusiastic at times. The SIT-1 seemed the perfect foil to help tone things down a tad and really bring the Druids into their own, especially with a bit of warmth and body dialed in via the bias knobs. As far as volume and headroom go, I had no reservations whatsoever. As with the F7, a volume setting around 11 to 12 o’clock gave me all the oomph I needed. This setup really let me stretch the Zu speakers out a bit and hammer out the SPLs. Going loud, I didn’t get the impression that the tone hardened up or that the soundstage collapsed. These puppies can pound away and sound great doing it, even driven with the measly 10 watts per side. I had no problems getting Natalie Merchant up to realistic levels, with no nasties working their way into her voice at all: no sibilance, glassiness, or anything else. She just got louder, with no sense of strain whatsoever, even to the point of sensing the sound waves hitting my chest and making me “feel” the music. Simply speaking, the SIT-1 breezed through the sample music cuts, all at high enough volume to make the speakers work a bit, without missing a beat. Enough said.
What happens, then, when we ask the SIT-1 pair to drive less efficient speakers such as the Carbon 7s or the SCM19s? Well, let’s find out.
Starting with the Fritz Carbon 7s, I found that I had to run the volume up to somewhere between 1 and 2 o’clock to get to the upper end of the volume level at which I comfortably listen. Others might prefer to listen at even higher levels, so be forewarned that headroom might be starting to limit with speakers at 89 dB efficiency. Was I happy? Well, yes, as happy as a pig in mud. As with the Zu Druids, this combination is one I could happily live with, and I mean for the long haul. Interestingly, the normally warmish Fritz monitors sounded quite similar tonally to the Druids, which I normally consider to be a more aggressive, up-front sort of speaker. I don’t think the Carbon 7s sounded any warmer and more dimensional than usual, but rather, the SIT-1s seemed to reign the Zu speakers in to approach Fritz territory with regard to warmth, smoothness, and lack of sibilance. Again, the Carbon 7s easily performed their disappearing act, almost removing themselves altogether from the soundscape.
Via the Carbon 7s, the SIT-1 amps realistically reproduced the nuances in the massed strings in the Alwyn Sinfonietta. Plenty of dynamic and energy were apparent too, giving a more than decent facsimile of a large string ensemble playing in a real space. String tone was pure and present, with just the right touch of silky texture. I was equally drawn in to the level of detail this system was providing, as I could easily hear the occasional bow tapping a music stand, and even page turns. As I said previously, the Carbon 7 speakers sounded a lot like the Zus with this amp; if I had to get nit-picky about small differences, I’d say that the Carbon 7 had an ever so slight hoodedness to the string tone, leaving it just a bit regressed compared to the inner luminescence provided by the SIT-1s driving the Druids. Perhaps I sensed just a bit more openness and extension with the Zu speakers?
Oh, and Natalie sounded fantastic as well.
All right, then. Let’s up the ante a bit more and toss the ACT SCM19 monitors into the mix. At 84 dB efficiency, these ought to give the 10 watt per channel SIT-1s a challenge. And indeed they do. Yes, sound was produced, and it was wonderful, but I was definitely approaching the headroom limits of the amplifiers. As I ambled toward the limits of the volume control, I noticed a slight curtailing of the ultimate dynamics, but then again, I was playing the music considerably louder than I normally do. I mention this situation only because I know the majority of listeners enjoy their music at higher volume levels.
Even considering these limitations, I found the SIT-1/SCM19 combination to provide some of the smoothest, best-resolved listening I’ve encountered. It’s just sublime, with its lack of grain or overemphasis of any part of the audio frequency band. I’m taken back to those times when I listened to single-ended triode amps driving fine speakers within their limitations. The Mozart Laudate Dominum is a perfect example… The soprano solo voice was just so pure and enticing, hanging there in mid-soundstage with so much airiness surrounding it. And the mixed choral voices sounded so integrated, as if a single voice emerging from the dark background. By the end, I was (begrudgingly) willing to trade-off some ultimate volume and headroom just to enjoy the beauty of what I was hearing.
All told, I found that the real strength of the SIT-1 amplifiers is to produce liquid, grainless, and extended tonal character with a sensually realistic dose of natural spaciousness and hall ambiance. The amps were an astounding success with all three speakers, but their ultimate power/dynamic limitations must also be considered for any speakers with efficiencies less than 90 dB.
First Watt J2
Finally, we introduce the oldest design among the three amplifiers under review: the First Watt J2 stereo amplifier. Just because it isn’t one of Mr. Pass’ most recent designs doesn’t mean that it should be discounted. In fact, I firmly believe that the J2 is probably the most versatile of the First Watt offerings, which means that it may well speak to the largest audience of audio enthusiasts. First off, the J2 is the most powerful of the amps on parade here, offering up 25 watts per channel into 8 ohm speaker loads (but only 15 watts into 4 ohms). Secondly, it’s the only offering of the bunch that gives the user the choice between balanced and unbalanced inputs. That attribute alone is important to me, as the Antelope DAC that I use offers high-gain balanced outputs as well as lower gain single-ended outputs. When working with the lower powered First Watt amps, I want all the gain I can get, so it makes sense to use the balanced outputs from the DAC. Recall also that I use the passive volume control on the DAC in order to keep the signal path as simple as possible. With the other amplifiers, I had to use XLR to RCA adaptors to access the high-gain outputs, and I think we can agree that this solution isn’t optimal.
For my evaluation of the J2, I went ahead and used balanced interconnects between the DAC and the amp … well, because I could.
Again, starting with the J2 powering the Zu Audio Druids, I got an exciting, fast, and punchy presentation of the music. All of the positive attributes of the Zu speakers were in play, and most importantly, I didn’t sense any hardness in the treble, especially in the upper registers of the violins, as I had with the F7/Zu combination. Perhaps the highs were a bit more extended and lively than they were with the SIT-1, but it was just that … more energy; not shrillness or hardness or glassiness of any type. Also, as expected, there were no issues with headroom and dynamics, as there seemed to be plenty of power in reserve, even when playing back the Alwyn Sinfonietta at mid-hall concert volumes. Soundstage and imaging performance were quite good, and certainly on par with what I had heard with both the F7 and SIT-1 amplifiers. The amp merely let the speakers get out-of-the-way, but not quite disappear.
Solo soprano exhibited plenty of energy and presence via the J2/Druid pairing. Perhaps there wasn’t quite the sense of silky smoothness I heard when using the SIT-1s, but the extension and presence were greatly appreciated and enjoyed. The J2 also did a fine job of letting the microdynamics of the female voice shine through, as I easily registered those slight variations in tone, texture, and volume that a really good vocalist can call upon when required. Oh, and the massed choral voices …. Oh my!
Moving on to Natalie Merchant’s “River”, the synthesized opening had plenty of punch and texture, and when Natalie made her entrance, I sat up and took note. The full harmonic punch of the vocals was there, along with extension, dynamic, and inflection. I felt almost like I was there when the recording was being made. When the Zu speakers really get up and go, the listener is transported. Again, maybe the overall presentation wasn’t as smooth as it was with the SIT-1, but the realism and electricity more than made up for the slight lack of euphony.
On then, to the Fritzspeaks Carbon 7 SE. Here, music reproduction was gutsy, powerful, and yet smooth. I could feel the guttural tones of the lower strings, punching their way through the wall of sound during large crescendoes during the Alywn piece. Individual cellos and violins sounded meaty and present, yet with enough finesse to never become overbearing or overdone in tone. I could appreciate the underlying power and control offered by the J2 relative to say, the SIT-1. One property that all of the First Watt amps have, but which really shines forth with the J2 is its quality of inner fire and incandescence. It has a way of making natural, un-amplified sounds come alive and tickle the listener’s fancy. While I heard this characteristic with the J2 driving all of the speakers, it somehow really called attention to itself with the Carbon 7 SE speakers. These same attributes in spades were also offered up with the vocal parts in the Mozart and Natalie Merchant cuts, coupled with the exceptional soundstage and imaging presentation these First Watt amps project across the board.
Finally, I am pleased to report (yet not at all surprised) that the J2 had absolutely no issues at all driving the ATC SCM19 monitors. Even at 84 dB efficiency, the J2 doubled down on these guys without skipping a beat. I was rewarded with all of the volume I can comfortably live with over extended listening sessions, and then some. Dynamics, both on the large and small scale, were fabulous as well. I was honestly and pleasantly surprised that I could get away with using any of the First Watt amps to drive these power-hungry hogs of speakers, but they did! If the SIT-1s were pretty much at their limits dynamically with the SCM19s, the J2 was right at home, and that makes me happy. Very happy. Cranking Natalie Merchant to uncomfortable volume levels barely took me to the 12 o’clock position on the volume knob, so there’s plenty of gas left in the tank.
Coupling the J2 with the SCM19s really serves to remind me of those speakers’ studio monitoring heritage, as the sound produced was exceptionally clean, yet warm and pretty enough to pull the listener in for long, enjoyable, and non-fatiguing sessions. They just do so many things right in my book, and the J2 drives home exactly why I find this to be the case. There’s an element of smooth, grainless purity in the upper midrange of Natalie Merchant’s voice that I just don’t find to quite the same extent when listening to the other speakers, and the J2 emphasizes this difference as obviously as I can imagine.
Looking back on this somewhat unique experience, I see that I’ve spent a lot of hours listening to these three Nelson Pass amps. Heh heh. Anyway, I was impressed right from the get-go, and I remain so. While the three designs differ a bit from one another sonically, there’s definitely a family resemblance throughout. So, in summary:
- If you want more power, dynamic, and fire in the belly, go with the J2, as it’s probably the most versatile of the amps in terms of its ability to drive a range of speakers;
- If you want the ultimate in smoothness and tube-like harmonic glow, and are willing to work with speakers with efficiencies above 90 dB, give the SIT-1 a try;
- If you want a nice middle ground between what the J2 and the SIT-1 have to offer, then hang your hat on an F7.
Which would I choose? Good question … I’d say for the range of speakers I actually own and use on a daily basis, I’d probably go for either the F7 driven by an active preamp or the J2 without the preamp. Right now, I’m experimenting with the F7 coupled with Linear Tube Audio’s microZOTL 2.0 serving as a line stage preamp, and I’m totally digging the sound. Even driving the ATC speakers, this little combo has plenty of get-up-and-go, and would make me a happy camper for a long time to come.
So ultimately, I’d say that Nelson Pass has rather succeeded with the First Watt family by offering up funky, really cool (actually hot) amplifiers that will fit the bill for a certain segment of the audiophile population who yearn for pure, highly satisfying sound played at real world volumes. Count me in!
About the Author
John is also a professor of analytical chemistry and forensic chemistry consultant in his spare time when he isn’t listening to music or evaluating gear. He tries to fit in plenty of time to hang out with his two teenage kids, his lovely wife, and the family cat, though only the cat also seems to harbor audiophile tendencies. John also enjoys running, cycling, golfing, hiking, or just about any other activity that sucks up time and money.