FirstWatt SIT5

by Dawid Grzyb / December 20, 2024

Shortly after landing my FirstWatt SIT4 story, I learned about a more powerful mono version of this amp named FirstWatt SIT5. Recently it was sent my way and now it’s time to tell its story. Enjoy! 

The two SIThs

The end of the year just before the holiday season is the perfect time to sum it up. Of all the products I got my hands and ears on in 2024, the Aavik I-880 integrated and FirstWatt SIT4 power amp are my two standouts by far. Not only this, in my private roster they also list as all-time bests in their respective categories. This essentially means that neither I’ve ever heard an integrated machine anywhere as good as the Aavik, nor a low-power specimen that comes any close to the FirstWatt. Both were awarded with our Victor badge to stress that point. Since this review tackles the latter’s beefier twin-box sibling, it’s fitting to narrow today’s scope only to their brand, which its founder Nelson Pass sees as his kitchen table. Therein he experiments with cleverly simple amplifier circuits of low power output, which are usually tailored for non-mainstream loads of special needs. More times than not these amps also incorporate unobtainable transistors only Nelson has in limited stock. Once these parts are gone, they’re gone, and then so is the FirstWatt model built around them. Thus far that’s 15 designs in total.Should you want high output power and nice casework atop Nelson’s experience and know-how gained over decades in the industry, his primary business Pass Labs has you covered. This lineup comprises audio hardware for wide audience with wallets deep enough to play there. Meanwhile, FirstWatt amps are for those enthusiasts who appreciate great sound and are smart enough to look past their modest sticker and alike visual appearance. This limited lot is also for those who understand that just few quality watts is more than enough for their high-efficiency speakers. That said, it takes a particular listener intelligence and awareness to fully appreciate what FirstWatts have to offer. They’re not for everyone, which I think is also a part of their appeal. We live in a time when there is no shortage of upper five-figure amps out there on the market. Over the years I’ve sampled a fair share of these. Meanwhile, my recent SIT4 story describes a $5’000 stereo power amp that to my ears is out-of-this-world good as far as sound quality is concerned. So much so in fact that I’d happily put it against any other low-power design no matter its type or price. On an even more private note, I’ve been constantly thinking about this machine ever since its departure to Srajan’s.If the audio industry has us convinced that top performance demands fancy exterior, large size and high price, then the FirstWatt SIT4 on the job with fitting speakers bluntly proves us otherwise. In that sense this particular amp defies the usual well-established MO so brilliantly, that I like to think of it as a pygmy hiding an outrageously large and very sharp knife. You won’t think much upon seeing its inconspicuous dress code and footprint. When it starts to make sound however, that special blade goes to work and quickly leaves a bloody mess behind. The gifted pygmy grins, corpses drop one at a time. Their market status matters nothing, no one’s safe. To illustrate, my 9x dearer 995R monos weren’t either. Meanwhile, SIT4 owners with their audio mainstream days long in the past will find that gory bit hardly a nuisance. Those who don’t should know that the unique Tokin THF51 Jfets inside the amp in discussion are largely the reason why it sounds the way it does. These industry-grade Static-Induction Transistors aka SITs boast triode-like curves, 50MHz bandwidth and 600V/30A/400W ratings. More importantly, they allowed Nelson to design a solid-state circuit that pulled triode-like sonics without output transformers, tubes and and all the usual hassle associated with them. To quote myself: “Tube aficionados happy with its cost-effective visually plain aluminium box instead of the usual shiny kit with protruding glass may find that a win-win scenario. Many FirstWatt shoppers actually do.”Some two weeks past going live with my SIT4 story, Nelson had a nice update for Srajan and yours truly. At that time he had SIT5 mono amps operational. Fast forward to late November. Two boxes with them inside showed up at my doorstep. Apparently Santa came early this year. To get the basics out of the way, the newcomer does 35/60wpc into 8/4Ω (@1% THD, 1kHz), so respectively 3.5/12x more (!!!) than the SIT4 and with 1% lesser distortion. The former’s 0.32Ω output impedance translates into a damping factor value of 25, so quite the increase in the context of the SIT4’s 4Ω/2. This is all we need to know that the SIT5 was clearly designed with far tougher loads in mind. From Nelson’s personal comments in the product manual we also learn that the significant disparity in power output between the two SITs is only a part of the story. The stereo version’s two key Tokin SITs operate in the Common-Source mode, where they supply both voltage and current gain. Each SIT5 mono houses a single SIT transistor that operates in the Common-Drain mode, where it only has to follow voltage, which secures lower output impedance, lower measured noise (30uV versus the SIT4’s 75uV) and higher bandwidth (5Hz-200KHz versus the SIT4’s 5Hz-80KHz). In the manual Nelson also mentions that we shouldn’t expect the two SITs to sound the same.FirstWatt enclosures and linear power supplies are unified all across the roster, so each SIT5 measures and weighs the same as their stereo predecessor. That’s (W x H x D) 43 x 14 x 38cm and 14.5kg. The two models also share 100kΩ input impedance, constant 200W power draw, exclusive class A bias, one output device per channel and no feedback. It’s worth to remember that these Tokins can go up to outrageous 400W. In Nelson’s application they don’t because the standardized FirstWatt housing is far too small to tap into that beefy reserve. The SIT4’s frame busy with just one pair of these parts set in the cruise mode already ran very hot. In SIT5, a single Tokin transistor has the same area just for itself to dissipate heat into, which explains how it achieves far more usable power from the same aluminium box. Since there are two in the set, $10’000/pr is the easy math. Should you see it as quite the expense for a FirstWatt machine, it is. There are however two important things to take into account here. One, today’s mono set promises us compliance with speakers significantly beyond the SIT4’s comfort zone. That alone is a major asset. Two, if the newcomer is any close on sonics to its gloriously voiced stereo sibling, rest assured that’ll already be more than worth the extra money and rack space. Without further ado, let’s now dive into how this twin-box design goes about its business.To do that, some additional context is needed. In my SIT4 review I wrote that, as magnificent as they are, Vox monitors don’t have enough cone surface to sound like a larger product. I don’t mind that they struggle at high SPL, because they’re not meant for such stunts anyway. Or are they? The SIT4 turned that notion upside down. To quote myself: “Its contribution to the bass output of the Vox resulted in its optically grander sensibly tauter profile that also embedded copious amounts of additional ease. I hadn’t seen that coming. For some reason, and I can’t quite wrap my head around this, the Swiss felt more authoritative, controlled and complete with this 10wpc monster than with any other amp I’ve tried, and there were many. Heck, even my 55wpc monos produced calmer, bloomier and muddier lows with this load. I don’t have to know how the SIT4 tapped into my daily monitor’s hidden reserves. What mattered more was the result, which to my ears was the potent base for the additional gains in immersion. The Vox already is wicked in this department and so is the FirstWatt. Their combination effectively squared the mental factor and got me to the place where I haven’t yet been with these speakers. I haven’t yet heard them this accurate, grounded, intense on color, seductive, hydrated, spatially majestic, enveloping and alive at the same time, all in all gorgeous. Some would call this magic. I call it the most wholesome Vox sound to date. Should you crave those long-forgotten teary-eyed moments when listening to music, this is how it’s done.”The Vox fronted by the stereo SIT sounded in a way that I can only describe as unadulterated personal bliss. The amp’s sticker made that state even more surreal, appealing and intoxicating than it already was. When that story went live, I wondered how much of the predecessor’s special sauce its mono siblings inherited. The key component with its triode curves and exclusive class A bias guaranteed a fair share of that goodness, while higher power output and damping factor promised a sportier profile, possibly built upon a touch leaner, more firm and quicker bass. This early guesswork turned out to be largely true. Vox monitors fronted by SIT5 mono amps scored silly high on all the counts as per the quote above. My ears however registered even more nimble yet lighter downstairs department, additional radiance and a touch less enveloping spatial presence. These were no major changes by any stretch, but enough to consider the usual Vox sound as more caffeinated, alert, intense and all in all uplifting. That would make the SIT4 somewhat more grounded and relaxed, but I can’t be sure without having it nearby. I’m certain how I felt about the SIT5/Vox combo. In essence, it granted me access to the same kind of rarely heard joy and completeness.If I had to select a SIT only for the Vox in my rather small 22m2 room, the terrific stereo version would’ve been it because it’s one box priced at half today’s expense. The Swiss also benefits from its lower damping. When demanding loads come into play however, these strictly practical considerations become irrelevant. Then thinking about a suitable companion amp that makes such speakers happy is a must. On that note, Boenicke W11 SE+ floorstanders enjoy the following three things; damping, power and space around them. The more, the better. If these criteria aren’t met, then spatially flat, piercing and ethereal sound with wonky quite unlistenable bass is the result. To put it mildly, using SIT4 with the W11 SE+ would be the pinnacle of counterproductive hardware matching. SIT5 monos on the other hand make far more sense for this challenge, even though their specs don’t read as ideal to extract the very best out it. No matter. Practice proved me otherwise and very quickly at that.I haven’t the foggiest how the 10wpc SIT4 made Vox more authoritative, controlled and feistier that the stationary 55wpc 995R hybrid monos, but it did and without any compromises at all. While this was quite the stunt worth all the flattering, I carefully assumed that with the W11 SE+ and SIT5 such a high-tiered outcome was off the table. Let’s call it a reviewer’s common sense and personal experience. Sometimes that fails. If my daily floorstanders have high needs to hear them at their best, then today’s FirstWatt had in store some valuable lessons on speaker drive. Underpowered and insufficiently damped bass of regular speakers is shy on heft, shallow and excessively boomy, so troublesome for the range above. Should we go higher with volume to offset what’s missing, these symptoms grow stronger to bluntly communicate hardware mismatch. The SIT5 with the Boenicks netted the exact opposite result that comprised remarkable low-end extension, proper bottom fill, spot on control, power, effortlessness and quickness without a hint of turbulence or hollowness. Squeaky clean, highly elastic, thoroughly sorted output, all in all brilliant. In spite of its might, bass wasn’t the key attractor. Although fully engaged when needed and thunderous upon demand, it remained elegantly supportive, like a skilled drummer who understands that setting the pace for the entire band and elevating the other members is its key job.Speaking of, All Boenicks are imaging fiends. The W11 SE+ adds high-tiered clarity, articulation, accuracy and illumination to that, too. The trick is in not overdoing on these fronts, as otherwise the result becomes shouty, glassy and piercing. The inherently juicy, smooth and texturally extremely gifted SIT5 prevented that. It assisted the W11 SE+ in portraying all the outlines internally hydrated and hefty within space of gargantuan proportions. The key instruments and vocals were close, emotionally infused and large in accordance with a given track’s demand. The takeaway was elsewhere. The SIT5 played the terrific enabler for speakers that to my knowledge desperately need way more muscular amps to truly shine. Live and learn.Of all the amps I tried with the W11 SE+ over the years, the Aavik I -880 was the best to date. It does 200/400wpc into 8/4Ω, boasts vanishingly low output impedance, sells for €67’000 and sounds truly spectacular with these floorstanders. While I’m confident that with the Boenicks it produced even more crackling, tectonic, slamming and visceral sound than the SIT5 now, I won’t risk naming today’s specimen as any less eloquent, sublime or immersive in comparison. To my ears the new FirstWatt is as gifted on these counts as the SIT4 wonder. The former represents the same peak performance in all regards which make music so captivating, sensual, magical, expressive and profound. While I know quite a few amps truly amazing in one way or another, the two latest SIT models offer a particular kind of suchness that I don’t think I’ve encountered in any other similar machine. I’m not saying that it doesn’t exist. At this time I just don’t know about it.Let’s quickly return to the speaker drive. To check whether I’m sane, I asked my buddy Matt for some 20 minutes of his precious time, which was enough to compare the SIT5 to 995R monos with the W11 SE+ on five songs. The man had a listen for a minute, then I muted playback, swapped speaker cables, unmuted, pressed play and asked about his feedback 60 seconds later. On Tool’s “Prison Sex” Matt fancied my amps more because to him they sounded gutsier and chunkier. “Forget” by Lianne La Havas was the opposite, because her voice and all the other sound sources were to his ears (and mine) more articulated, nuanced and smoother. Matt also appreciated the SIT5’s more elaborate textural qualities, spatial order and higher background cleanliness. Eivør Pálsdóttir’s “Trøllabundin” had him surprised. The 995Rs were lazier and somewhat itchy on the track’s key vocal line. At that point he started to understand what was going on. He just had to accommodate. “Dancer” by IDLES was the final clincher. Here the SIT5 was described to me as the one that dug deeper and acted gutsier and more firm, but also quicker, dynamically charged, elastic, less elevated in the critical boomy range and superior in limiting claptrap embedded in this song. The same story was with “Colossus”, also by IDLES. For shits and giggles I asked my buddy whether he’d like to return to the starting point and Tool. “No need, don’t push it” was his answer. Although Matt’s observations reassured me that I haven’t yet lost touch with the reality, the most valuable upshot wasn’t that. His feedback was instant, precise and without any second guesses. That was yet another reason for me to consider the gap between the two amps as truly large. Let’s wrap.

There’s only one thing to say here. FirstWatt SIT5 gracefully follows the SIT4’s accomplished exquisite profile minus the latter’s load-related prerequisite, which means that it offers the same kind of magic for wider audience. It’s really that simple. While it doubles energy consumption, heat generation, price and shelf space requirements, those are all highly realistic demands considering what we get in return. One may spend a lot more on an amp and get nowhere near the SIT5’s sonic excellence. At this time I have no clue what does it take to outshine this casually dressed two-box affair where it matters. I truly don’t. My tip of the hat to Nelson & Co. for landing today’s SIThs and effectively showing me where the performance ceiling is. Shortly these loaners are going to be forwarded to Srajan, so I encourage you to watch his space.

Associated Equipment:

Retail prices of reviewed components in EU (excl. VAT):

  • FirstWatt SIT5: $10’000/pr

 

Manufacturer: FirstWatt

 

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