Nautilus Headphone and Stereo Tube Amp

Description

The Nautilus is our flagship Personal Audio Tubed Integrated Amplifier.

The Story of the Nautilus is born of the same process that brought the Zions. We set out to build my private amps apart from ampsandsound. These were to be mine without branding and never to leave for demos. All too often, my own listening space was sacrificed for the need for demo stock. I choice the HK Cit II as my inspiration point. From that seed came my own Cit II Monos build on turrets just like the best amps of the golden age. Ampsandsound followed with the Sulo monos. The Sulo and Leeloo monos brought turret-based construction and our highest performance to personal audio, but the dual mono layout is not for everyone.

The Nautilus brings the dual-mono layout onto a single chassis. We start with our most versatile circuit, the Mogwai, and go about creating two separate amps that share a single chassis. 2 Power Transformers, Separate Power Supplies, Chokes, and input transformers. The amps are built with separate turret boards, with the one shared component being the input tube, volume control, and outputs. We were unconstrainted with parts selection and layout and chose the most robust power transformer and widest/least distortion output transformers we could find.

The Nautilus’ hand build nature and part selection necessitated a robust hand fabricated chassis. We partnered with our existing CNC metal fab house to build a 12 gauge steel chassis with bracing that could support the 40lbs of transformers without a hint of strain. In total, the Nautilus is 55lbs before packing. We additionally choose to cover all the transformers and business end of the amp with a gorgeous chrome cover.

The Nautilus is a classic and decidedly prosaic design, as it employs turrets and point-to-point wiring & there is no silicone, ICs, or regulators. We consider this a standard-bearer of purest audio with an American sensibility. The Nautilus is built in a way few modern amplifiers are. This is not due to intrinsic inferiority, but rather it is impossible to rush and is incredibly expensive to produce. Some of the most familiar tube amps ever produced utilize this method, including; McIntosh, HK, Leek, Quad, & Western Electric. These amplifiers demand to be played and built to last a lifetime.

The Nautilus does not use a voltage divider network but depends on transformers instead. We use multiple dedicated taps for headphones to offer a dedicated selection for the most comprehensive range of headphones.

The Nautilus has been described as a tube integrated amp for personal audio users. We mean by this, the Nautilus allows for five separate impedances to be selected for system matching and has a pair of 8ohm 5 way binding posts. The speaker vs. headphone output is selected with a small toggle switch on the back of the amp. This simple addition was not without compromise. You can choose between headphones or speakers without wiring changes to your system.

Transformers are one of the most special aspects of the amps. The Nautilus performance is made possible with custom wound ultra-high quality output transformers from Transcendar, which provide excellent frequency extension and a flat response.

Cinemag transformers are used as input transformers for XLR to RCA conversion.

The input of Nautilus unitizes input transformers for reduced noise floor, greater clarity, and sub-bass response.

For this reference amplifier, we paired the finest coupling caps, Jupiter copper foil in wax caps. The increases in micro-detail retrieval were remarkable.

Volume control is handled via a 24step stepped attenuator. This ensures precise channel matching.

The Nautilus allows for a wide range of tubes, including 6l6gc through KT90s. KT120s and KT150s are not compatible. The tube complement form factor is spec’d as a matched pair of 6L6GC STR or KT88, a single 12AX7, and two 5AR4 or 5U4 rectifiers.

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

Bench report with 5751 inputs with 5ARA4 recifiers and KT88's

Input sensitive: with 5751 input @ 1.72V P-P

Noise: @ 300ohm/HiZ 1.33mV RMS

Noise: @ 100ohm 1.1mV RMS

Noise: @ 32ohm 650mV RMS

Noise: @ 8ohm LoZ 430mV RMS

Max Power @ 8ohm @ 8watts RMS

Max Power @ 32ohm@ 5watts RMS

Max Power @ 100ohm @ 6watts RMS

Max Power @ 300ohm @ 6watts RMS

Ultra-wide bandwidth; 8hz to 26khz @ 1 watt

Compatible with nearly every headphone.

Power and Noise specs are dependent on tube selection.

Actual size is 17.5"wide, 14.5"deep, 7" tall

Amp weighs in at 68lbs/93lbs shipped in a large Pelican style case.

Black base/Matte chrome cover.

Additional colors are possible as a special order... please call or email for details.

The all ampsandsound amps are handmade in Southern California with custom hand-wound output transformers and U.S. sourced parts.

Our amps are handmade by a small team, with quality being our first priority.

Nautilus Positive Feedback Review

As both a reviewer and a consumer, I read a lot of reviews myself. I often see solid state amplifiers being commended for having tube amp like qualities in their mid-range presentation, or tube amplifiers being commended for having solid state bass or speed. I myself have used these same euphemisms to describe some of my all-time favorite amps and thought they made a ton of sense.

However, as I have worked on this review of the ampsandsound Nautilus over the past three months I have chosen to re-evaluate whether I should be using these euphemisms in my vocabulary, both as a reviewer and a consumer. The reason for this re-evaluation is that the Nautilus has presented me with an amplifier that has no compromises that would easily allow a listener to identify its underlying topology. I would describe it as not bright and edgy, nor warm and flabby, instead vocals are rendered with realism that is simply shocking, and the sound is extended from the deepest depths all the way to the highest peaks without a hint of fatigue. It is simply a reference class amplifier quiet enough to be used with headphones, and powerful enough to be used with mid to high efficiency speakers. It defies categorization, and even at its $9200 price tag it provides value for the money in spades, based on both its performance and its build quality.

TONEAudio Magazine Issue 108