September 28, 2022 7 min read

Grover reviewed a pair of Ampsandsound Zion Monos, and I don’t think he’s been the same ever since. The Zion Monos are the highest output amplifier in the Ampsandsound family at an extremely conservative 42 watts per side. However, most of Justin’s creations are single-ended triodes (both conventional and directly heated) of the flea-watt variety. Many of these amps have garnered much praise in the Head-Fi community.

The Ampsandsound Nautilus is the flagship of the headphone amp line and was designed to do double duty as a power amp for efficient speakers. I was skeptical that the Nautilus, at about five watts per channel, would have enough juice to rock my two-channel world. What would it sound like powering a pair of $100,000 Von Schweikert Audio Ultra 55’s? Game on.

Ampsandsound Nautilus In Use

Let’s jump right in and get this party started.

The Ampsandsound Nautilus arrived in a large Pelican-style case, packed with custom-cut foam. It was simply a matter of pulling it out and putting in the five tubes, two 6550s, a 12AX7, and a pair of 5ARA4 rectifiers. The Nautilus is a dual-mono affair in a single chassis–totally separate power supplies, hand-wired, point-to-point construction, all in a simple but gorgeous chassis. Extremely over-spec’d output transformers rated at 60 watts and designed around power tubes using no feedback. These are just a few of the things that hint at the glory of these amps, and how capable they can be.

One thing I noticed during my time with the Ampsandsound Nautilus was this: unlike lots of other gear I’ve used, it didn’t require a long break-in or warm-up time. Flip the power switch, and after it takes a minute or so to come to life, in 10-15 minutes, optimum goodness is achieved. I regret not taking the time to do any tube rolling, but simply did my listening with the supplied tubes. My later experiences doing extensive rolling with other Ampsandsound amplifiers have confirmed that unless someone is quite the experimenter with access to lots of NOS tubes, (and after a particular sonic subtlety), there’s a very good chance that the tubes supplied with Ampsandsound products are about as good as it gets.

At the time of review, I had several speakers to try with the Ampsandsound Nautilus: Von Schweikert Audio Ultra 55, Credo EV Reference One, my QLN Prestige Fives and the Acora SRC-2. I also borrowed a pair of stand mount two-ways by AudioVector. Additionally, I tried my Audeze LCD-X and SennheiserHD-650 headphones.


The headphone demo was especially fun. There are no less than five different 1/4” headphone jacks on the front panel. These jacks are labeled with the impedance–Lo, 16 ohm, 32 ohm, 100 ohm, and Hi–to match your headphones. This is very cool. In practice, I found that the different taps can be used to effectively fine-tune the sound of phones. My LCD-X sounded amazing but the shocker was just how much better my Senn 650s sounded. I literally was not aware of how far the 650s can scale in sonics when driven by a phenomenal amp with the proper output impedance. In keeping with the Ampsandsound philosophy of sonics over cost-cutting measures, the different impedances are sourced from separate taps of the output transformer windings instead of a voltage divider network.

When using the Ampsandsound Nautilus to drive loudspeakers, a small, rear panel-mounted toggle switch is used to select the power output to speaker terminals. This set of high-quality five-way posts is sourced from the 8 ohm transformer tap. Also on the rear panel are both RCA and XLR inputs. The internal amp circuit runs unbalanced for simplicity and purity of sound, so there are high-quality Cinemag transformers to unbalance the XLR input. I used the amp with both inputs and honestly didn’t notice a big difference in sound either way. Justin told me the RCA inputs have a slightly wider bandwidth on the extreme top end.

On the front panel is the Alps stepped attenuator for volume. When using a line preamp to feed the Ampsandsound Nautilus, this volume knob can be turned to the wide open position, effectively removing it from the circuit. To leave no stone unturned, I tested the Nautilus with a preamp upstream and also by sending a phono pre or DAC output directly in and using the Nautilus volume pot. My Simaudio 310LP phono pre and an Ideon Absolute DAC each had plenty of juice to drive the Nautilus. It didn’t bother me that in this situation, the front panel volume knob was just a few clicks from wide open. Justin told me that he feels most of his amps like having some additional juice from an upstream preamp driving them. I can agree with that; however, I found a tremendously satisfying purity to the sound when putting sources directly in.

Ampsandsound Nautilus Sound

This was when things got really fun.

Despite Grover Neville’s raves, I was unprepared for what came out of the speakers. The Von Schweikert Ultra 55 was already in the system for review, so those were the first to get a dose of the Ampsandsound elixir. HOLY SINGLE ENDED TRIODE, BATMAN.

I had been massively enjoying the Ultra 55 powered by a pair of exquisite sounding VAC Master 300 amplifiers. If you look in the encyclopedia under state-of-the-art vacuum tube amplification, there is a picture of a Master 300. I had been using a pair of these bad boys, so the Ultra 55 was used to being told what to do by a total of 16 Gold Lion KT-88s. When I swapped out for the Ampsandsound Nautilus, and each speaker came to life with a single 6550 (strapped to run as a triode) at a raging five watts per side, I thought I saw the tweeters wink at me.

I started by spinning my most familiar records using a TW Acustic Raven LS turntable and Charisma Audio Signature One MC cart into a VAC Master Preamp (with built in phono stage), feeding the Nautilus with the volume pot wide open.

I was greeted with possibly the most enjoyably euphonic sounds I’ve yet to experience. On record after record there was a luxurious and smooth–but not dark–presentation. Yeah, the first thing I noticed was the music had absolute freedom from any grain, glare, and un-musical harshness. It was like all the treble detail, and midrange textures were there but polished by jewelers polishing cloth. The cliche vacuum tube soundstage seemed to be at Warp Speed 10. Depth and width dimensionality was dramatically enhanced. There was actual deep bass which might have been the most shocking thing.

The Ultra 55 is quite an efficient speaker, but it’s also a nominal 4 ohms and really wants some serious juice to live its best life. But of all the speakers I tried with the Ampsandsound Nautilus, it fared the best. The Credos came next followed distantly by the QLN, Acora, and AudioVector. There was not enough juice to get any of the other speakers going, with the least impressive match being the stand-mounted AudioVector two-ways. Not that anyone would pair a Nautilus with VSA U55s, but it actually worked.

No, it didn’t have nearly the sense of dynamic contrast, ultra-wide bandwidth, and musicality-with-neutrality as the VAC amps. Still, it actually worked well enough that I had many very enjoyable listening sessions using that combo.

There was a gorgeous delicacy to the sound that is part and parcel of its stylized presentation. By stylized, I mean for the speakers I tried with them, the Ampsandsound Nautilus is not amazingly neutral or a term I generally don’t like: accurate. There is a slight V shape to the tonality that favors the meat of the bass and the treble presence region. But the musicality, detail, and immediacy are at such a high level I never missed the extreme edges of frequency response at the very top and very bottom that lie on the outside edges of the V.

The Ampsandsound Nautilus does this thing where even though an experienced listener can hear its departures from absolute neutrality, there is a pureness to the sound that is quite addictive. The simplicity of the circuit (that doesn’t allow for much in the way of correction back towards more mission-critical cleanliness) is what I think enables this purity. The Nautilus sonic signature of purity of tone AND a liquid tubey goodness is quite a different sound than that of a tube amp that has a pleasant musicality to it, yet a musicality borne of additive distortion and pleasing colorations.

The Ampsandsound Nautilus never sounded slow or syrupy or romantic. It also starts and stops transients to display that coveted audiophile attribute usually described as the blackness between sounds. Or you could just say it’s hella quiet.

If I were a serious Head-Fi aficionado and craved the best in amplification, the Nautilus would be my pick. Its stylized sound when driving speakers was not as evident using my headphones. In fact, it seemed to improve the sense of accuracy I got when listening to the Sennheiser 650s. With my Audeze LCD-X, the sound was a little less transformed, but the Nautilus put everything I like about the LCD-X in a bolder yet cleaner context. Bass was big but very controlled. Mids were denser without any added confusion or mud, and the top end seemed to have just that much more sparkle.


What’s a Boy To Do?

Returning to my thoughts about using the Ampsandsound Nautilus to drive speakers, a few things echoed in my mind (to an almost annoying degree): should I consider looking for a high-efficiency speaker to own? Should I consider building something like a classic Altec 604E in its utility enclosure?

This line of thinking resulted in several conversations with Justin Weber. Justin is quite experienced in how to do such things, and I got the impression he loves sharing what he has discovered in his horn loudspeaker system journey. I mean c’mon, the man built his three-way horn system featuring custom-made wood multi-cell horns for the midrange AND tweeter compression drivers, plus a horn-loaded 15” woofer! He’s also built scads of Klipsch-inspired (but significantly different) systems, along with the previously mentioned dual-concentric, Altec-style boxes.

Maybe I’ll dabble at some future time, but I decided not to go this route at present. What about a higher-powered Ampsandsound amp?

Conversations along this line lead me to purchase a pair of Ampsandsound Bryce Monos, which I love. Recently, I doubled down and bought a pair of his Zion Monos. And an Ampsandsound Jinx headphone amp for mastering work usage.

Yes, I am crazy.

Maybe I’ll win the lottery and end up with a VAC 452IQ or two, but for now, I’ll enjoy my Zions.

Hear ye, hear ye – calling all folks with high-efficiency loudspeakers, committed headphone fanatics, and possibly those with medium-efficiency speakers in small rooms: get your butt to somewhere you can hear a Nautilus or just take a leap I faith. You won’t be sorry.

Reviewers Choice award.


Words and by Dave McNair

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