First Watt SIT-3 Stereo Power Amplifier

Blurring the Line Between Tube and Solid-State

Equipment report
Solid-state power amplifiers
First Watt SIT-3
First Watt SIT-3 Stereo Power Amplifier

In hindsight, you would surmise that First Watt was rather lucky. When transistor manufacturer SemiSouth closed its doors in 2012, access to its silicon-carbide-based power JFET transistors (SITs) dried up. Fortunately, Nelson Pass had purchased a custom batch of these SITs in 2010, no doubt because this device’s characteristic curve resembles that of a triode vacuum tube and because it can work directly into a speaker load. The SIT-1 monoblocks and SIT-2 stereo amplifier, based on this output transistor, were introduced in 2012 and became the most successful in First Watt’s history, continuing in production through 2017. With only about 500 SITs remaining in stock (enough to make 250 amplifiers), Nelson wanted to release one more SIT-based design that was quite different in his view. As Nelson puts it: “I hope you enjoy the SIT-3. I think it is the most interesting of the First Watt SIT amplifiers, and for about 250 people it will be the best.”

The amplifier requires about one hour of operation to reach its maximum operating temperature. Final adjustments are made at the factory after an hour’s warmup, but the performance difference between ten minutes and an hour is said to be small. 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 30-to-60-minute warmup. And the level of improvement was not subtle. I would go so far as to call it fairly dramatic, and once I’d experienced it I sure didn’t want to start listening until the amp had gone through this warmup period. And so I started running the SIT-3 continuously and would only shut if off on days I wasn’t planning on listening. Nelson’s point is that the power supply capacitors are likely to last 20 years or more, and while they will slowly dry out just sitting there, they will have a longer life if the amplifier is not run continuously. 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. All this was in stark contrast to the musical fabric of Schiit Audio’s Vidar, an amp that I’ve actually taken a liking to. 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. However, there was one performance aspect in which the Vidar stomped all over the SIT-3, even in the context of a high-sensitivity speaker where the Vidar’s greater power delivery should not matter as much, and that was the bass range, where its superior punch and authority were on display. There is something about bipolar transistor amplifier bass performance that beats the crap out of MOSFET and JFET designs. I don’t know what it is, but I love that bipolar bass crunch.

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. The SIT-3 was able to inject a touch of velvet and molasses into the midrange, which put a smile on this old tube lover’s face. As a result, I found the SIT-3 more musically compelling than the First Watt F7 that I previously reviewed. What makes the F7 so special is its inherent textural sweetness and warm tonality, and it’s in these areas that the SIT-3 actually outgunned the F7. I’m not suggesting that the SIT-3 is euphonic to the point of dominating a speaker’s personality. It isn’t. In fact, its textural flavor is very much dependent on that of the associated preamp. It readily takes on the preamp’s persona. One of the most enjoyable couplings was with Merrill Audio’s Christine preamp, which is capable of dishing out the most luxurious textures I’ve ever experienced from a solid-state design.

Just for the hell of it I hooked up the SIT-3 to my recent loudspeaker acquisition, the Innersound Isis Mk 3.5 electrostatic. Roger Sanders refers to the Isis as a fine little speaker. I think he’s being far too modest—it’s a terrific 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-57. The SIT-3 was much happier with the Quads and was able to generate a believable tonal balance within an expansive soundstage. It did justice to the midrange, but did not equal the dynamic excitement generated by my Futterman H-3 amplifier, this being a marriage made in heaven and the best coupling I’ve found over the years for the Quads.

As with the F7, the SIT-3 is easy to embrace musically. It isn’t quite as resolving of low-level detail as the F7, but its sound is bit more natural and less forced and brings the listener a tad closer to the tube amplification experience with a far more incisive bass range than tubes can offer. Sadly, the SIT-3 represents the coda to Nelson Pass’ SIT adventures. The good news is that of all the SIT designs I’ve auditioned to date it is my favorite. And I don’t apologize for the fact that this somewhat funky push-pull design beats out a bunch of single-ended amps. 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.

Specs & Pricing

Power output: 18Wpc into 8 ohms; 30Wpc into 4 ohms
Frequency response: -0.5dB at 10Hz, –3dB at 50kHz
Input impedance: 200k ohms
Gain: 11.5dB non-inverting phase
Damping factor: 30
Output noise: 50µV unweighted, 20Hz–20kHz
Power consumption: 150W
Dimensions: 17" x 6.75" x 16"
Weight: 32 lbs.
Price: $4000

13395 New Airport Road, Ste. G
Auburn, CA 95602
(530) 878-5350

Associated Equipment
Speakers: Basszilla Platinum Edition Mk2 and OB3 DIY; Quad ESL-57; Innersound Isis Mk 3.5
Preamplifiers: Lamm Audio L2.1 Reference; Merrill Audio Christine Reference; The Horn Shoppe Truth
Digital front end: Apple Mac BookPro running Sonic Studio’s Amarra Version 3.4 software; DiDit 212se DAC, Sony XA-5400 SACD player with ModWright Truth modification
Analog front end: Kuzma Reference turntable; Kuzma Stogi Reference 313 VTA tonearm; Clearaudio da Vinci V2 phono cartridge; Sound Tradition MC-10 step-up; TPAD 1000 phonostage
Cables: Acrotec 6N, Kimber Kable KCAG Select interconnects; Acoustic Zen Hologram II and Wireworld speaker cable
Accessories: Sound Application power line conditioners, Monarchy Audio AC-Regenerator