When first heard the ampsandsound Nautilus at CanJam 2021, I remember it made a striking impression. I had turned on Frank Sinatra and Hoobastank songs and recall the sound being highly resolving with strong tonal density, control, and having a ballroom-like air; a very lively amplifier with an energetic expression. 

I obtained the ampsandsound Nautilus after selling the Bigger Ben Rev 2 and Agartha 2021. I decided to get the Nautilus after a suggestion by Justin, who helped me navigate the ampsandsound brand and other product recommendations. I opted to get one of the best offerings at ampsandsound and down-sizing from the amps I once had to own only one amp; however, I've now decided to keep the Kenzie and Nautilus and power them along with a preamp, the Garage 1217 Project Sunrise III, which increases the detail in the notes.

Many reviews on this website have been from my experience with ampsandsound. So far, I’ve reviewed the Kenzie OG Rev 2, Bigger Ben Rev 2, and Agartha 2021. I’ve enjoyed my experience with the products at ampsandsound, and this time, I have the Nautilus, a flagship offering.

I first saw Nautilus on the ampsandsound website around 2019 when I became interested in the Kenzie. It hadn't even crossed my mind to own one because of the price range and my situation at the time; it was more like something I might own as I "progressed" further in life. 

The Nautilus an amplifier built in a dual-mono layout into a single 12 gauge CNC steel chassis with bracing that supports the 44lb transformer without struggle. It has two power transformers, separate power supplies, chokes, and input transformers. The two amps have separate turret boards, with the shared component being the input tube, volume control, and outputs. The part selection was not constrained, and the most robust power transformers and widest/least distortion output transformers were employed.

The Nautilus has a classic and decidedly prosaic design, employing turrets and point-to-point wiring with no silicone, ICs, or regulators. This design is considered a standard-bearer of purest audio with an American sensibility. The Nautilus is designed and built in a way that few modern amplifiers are. It’s not due to intrinsic inferiority, but the Nautilus’ production process is impossible to rush and incredibly expensive. Some of the most familiar tube amps ever produced utilize this method, including; McIntosh, HK, Leek, Quad, & Western Electric. They demand to be played and are built to last a lifetime.

The Nautilus is a tube-integrated amp for personal audio users. It allows for five separate impedances to be selected for system matching and you can also select between headphones or speakers with a flip of a button in the back.

The Nautilus performance is made possible with the custom wound ultra-high quality output transformers, which provide excellent frequency extension and a flat response. Input transformers are used for reduced noise floor, greater clarity, and sub-bass response.

For the reference amplifier, ampsandsound paired with the finest coupling caps, Jupiter copper foil in wax caps, which increases the micro-detail retrieval.

The Nautilus also allows for a wide range of tubes, including 6L6GC, through KT90, but not the KT120 or KT150. The Nautilus came to me with a pair of KT88, a single 12AX7, and two 5AR4 tubes.

The Nautilus utilizes a single-ended Class A operation with zero feedback to provide the essence of sound, strictly old-school SET sound.

Keeping in mind that the sound is source-dependent, I use USB audio bridges like the Matrix X-SPDIF 2 or Singxer SU-6 or pre-amps daily, which I feel help clean the signal and affect what I hear to be a lower noise floor, giving more clarity and air in the sound. However, I now have the mindset of listening with the built-in USB before using USB audio bridges to see how it affects each DAC. At times I also use a pre-amp, such as the Garage 1217 Project Sunrise III, which I find gives the sound more note detail and clarity. For this review, I used the Singxer SU-6, Audio-GD HE-7, and Topping D90SE. 

Paired with the warmer HE-7, there is a bloom to the soundstage sound, giving the sound a still-much-nuanced depth. With the D90SE alone, there is still much more detail to be discovered when paired with the Singxer SU-6; with the Audio-GD HE-7 Amanero 384 (stock option), the sound is still quite muddy to my ears without a USB audio bridge, and a pre-amp only helps.

For my second listen with the Nautilus, I chose the Tung Sol 6L6GC, 5AR4's, and 5751 to pair with the Sennheiser HD 650, and listened to the Blu Swing & Shade - Jazzyster album. I was very impressed with the separation, impact, and detail.

The Nautilus uses Tetra tubes which have a thicker midrange, tonal density, and impact; and they kind of complement DHT or Direct Heated Triodes, which pull some of the mid-range back to allow the other ranges to have more presence. The Red October is the DHT equivalent of the Nautilus. I find both to be enjoyable to listen to, but I've yet to try the Red October. 

I wasn’t surprised by how good the Nautilus sounded when listening again. From the looks of the Nautilus alone, you can tell its packing power. Everything sounded very clean, thorough, and impactful. The decay is very good, alongside the resolution. 

One thing that set the Nautilus apart for me was how spacious and fully resolving all the details are. The scenery is very lush which is a characteristic of romantic ampsandsound house sound, but the completely resolving nature of the sound, possibly due to the huge transformer of the Nautilus, makes all the difference. Owing to both amps being of the Tetra family, the Nautilus sound is similar Bigger Ben, but the Nautilus is even more comprehensive. It is even more expressive through the powerful, well-controlled, tonal density that is detailed and rich in nuance. There is more extension, and the resolution is top-notch; it is a truly masterful sound.

The tonal density paired with the nuanced detail seems to be perfected in the Nautilus, and it’s like a smooth crescendo of music that fully extends and gives a certain magic to each note. The soundscape is rich, vast, and full of character provided by the details and ambiance. Paired with a neutral DAC like the Topping D90SE, you get to hear every bit of detail. This is noticeable in other amps with the D90SE too, but the sheer power that allows the details to follow through when paired with the Nautilus is highly satisfying. There is much more space and thoroughness in micro and macro detail and the atmosphere. Adding a pre-amp with the Nautilus turned to max volume added another dimension of micro-detail that honestly surprised me. It adds such depth and layering to the sound that makes it more engaging through the detail. I feel like I will never go without a pre-amp when listening to an amplifier again. It's truly amazing the level of detail and jump in clarity and quality that a pre-amp provides. 

Depending on the rectifiers you use, the Nautilus can be a neutral amp; the 5AR4 makes the sound more neutral and fast to me, but with 5U4G, there's more ambiance and musicality, and the 5U4G could be described to be neutral "where it matters". I like the 5U4G because it gives the Nautilus a liquid, musical sound; it's backed with a rich macro ambiance where the details play with grace. The experience could be described as a lush and full listening experience. It's natural and controlled as the notes extend; giving it a robust character and adding more life to the music. 

The power behind the Nautilus is felt through the presence of the notes. Detail is given the power to give grace to the sound behind the flow of the sound. The Nautilus adds onto aspects of what makes the Bigger Ben unique but gives it more power to give it more resolution to boot. That being said, the Bigger Ben has its unique sound as well, it could be said that the Nautilus has more power to dig into the music with even more power and stage to give it more richness. I must add that I didn't really try the Bigger Ben Rev 2 with the KT 88 very much when I owned it, and I wonder what the Bigger Ben sounds like powered with the tube that, I've read is kind the optimal tube for the Bigger Ben.

So far, one of my favorite tube combinations is with the KT88, 5751, and 5AR4s. The combination provides a clean, slight bloom to the music that I found very enjoyable. It's like a perfect, neutral sound that has great energy and detail. The 5U4G with the KT88 and 5751 is an excellent alternative for a more laid-back sound.

With the equipment that I have, I felt like all my headphones were more than adequately powered. The Sennheiser HD 600, 650, HIFIMAN HE 560, HE6SE V2, HE1000SE, and ZMF Verite all played with a beautiful, full richness, timbre, and dynamics.

Something about an amplifier like the Nautilus and the reason I’d recommend it is that it’s the end-game of the Tetra tube family for personal use that provides a fun sound that is deep, rich, and with full resolution. It’s a commanding sound that shines in precision, depth, and nuance in the notes with tube options to adjust the speed and attack. 

The Nautilus has a lot of power, and this allows any source you have to have strong control and expression of the sound. 

It should be noted that it's possible you may enjoy the DHT sound of the 300B better and may opt for the flagship equivalent, the Red October.

I’m still discovering how different tubes sound, but so far, with the JJ KT88, TungSol 6L6GC, TungSol EL34, JJ 12AX7, TungSol 5AR4, and PSVane 5U4G, and available source components, I’ve been able to gather some impressions. The EL34 with the 5U4G has tight, lean bass, and accurate, sparkly highs. Paired with the KT 88, the sound is more full and thorough with more presence and energy.

I remember having expressed that the timbre on the Agartha was one of the best I’ve heard from an amplifier. I’ve found that the Nautilus is of the highest quality and enjoyable, and in some respects, may be preferred.

For some reason, I thought that the TungSol EL34, not having Coke bottle shape, would not have enjoyable bass; but it’s a great, quality bass that meshes with the more nimble nature of the EL34. The Nautilus, regardless, gives shapes to notes and through its power, and again, we get to experience the magic of tubes at their fullest potential. 

The Nautilus sound provides a thoroughly grand listening experience that is hard for me to describe at times; perhaps I could call it perfect. It is so very precise, alive, and graceful. Being the most resolving amplifiers I've ever listened to, there is no way that I could not recommend it. To me, it is a perfect companion for personal audio and can be quite shocking to listen to as you hear just how rich, nuanced, and consummately expressive it renders the sound.

Product link: Nautilus Rev 2 - ampsandsound

Headphones: Sennheiser HD 600, Sennheiser HD 650, HiFiMan HE6SE V2, HiFiMan HE560 V4, HiFiMan HE1000se, ZMF Vérité Open Stabilized

Sources: Audio-GD HE-7 MK I, Schiit Modi Multibit, Yulong D18, Topping D90SE

Cables: Worlds Best Cables

USB: Matrix X-SPDIF 2, Singxer SU-6