OTOMON Laboratory — 音門ラボ

製作流れ — Work Flow

WORK & FLOW

Below is our amplifier manufacturing workflow. Each amplifier is built within 2–3 months, depending on the design.

01 — Technical Design

Designing the schematic and appearance

Based on each customer's needs, we design the amplifier to suit their system and budget. The more detailed your requirements, the more precisely we can design both the appearance and the schematic of the amplifier.

02 — Amplifier Building

Handmade point-to-point wiring

We prepare the internal parts, build the chassis to match the customer's design, then solder and wire the amplifier by hand. All wiring is point-to-point — we never use PCBs in our amplifiers.

03 — Technical Test

Technical testing after wiring

Once the wiring is complete, we run a full technical test. Here we verify that the amplifier works exactly as specified in the Step 1 design and meets all of our product standards — noise level, hum level, distortion, and so on.

04 — Human Test

Final test by the human ear

This is the most important stage of our manufacturing process. No measuring instrument is better than the human ear — even when the amplifier is almost finished, we still listen to the music ourselves to judge the sound.
We listen, adjust, test, and listen again in a loop until we are convinced the product is perfect. This stage takes a long time, and can sometimes take even longer than Step 2.

05 — Shipping

On its way to the customer

After listening to the amplifier many times and being fully satisfied with the result, we pack it carefully and ship it to the customer. All products are shipped via FedEx or EMS.

Building time: In most cases it takes about 2–3 months. Some more complex amplifiers may take longer than 3 months; in that case, we will discuss the timeline with you when you place your order.

哲学 — Philosophy

Our Philosophy

Every OTOMON product is designed and refined according to our own distinct philosophy of sound — with one purpose: to deliver the finest possible instruments to the most discerning listeners.

01 — 技術仕様

Technical data

Specifications are measured results — not the goal. Our aim is to build equipment that sounds beautiful, not equipment that measures beautifully. While our products consistently achieve good to excellent technical figures compared to commercial alternatives, those numbers serve only to confirm that the design contains no engineering errors. We could, in most cases, apply active techniques to make the specifications look even more impressive — but if doing so strips away originality or musical character, we will not do it.
At OTOMON, music is judged by the ear and no instrument can replicate the human 's ear.

02 — 真空管

The Wonder of the Vacuum Tube

The vacuum tube is not merely a component — it is a marvel of science. It has existed for over a century. Throughout history, it has been declared obsolete time and again, yet it persists — and grows. Each time it was written off, its beauty was rediscovered: a quality no other device can match or surpass. In high-end audio alone, the vacuum tube endures as a paradox of progress — never erased, defiant and inexplicable.

03 — 妥協しない

No Compromise

In all our designs, compromise does not exist as a concept. By the rules of good engineering, noise floor and harmonic distortion must fall within a defined range. A small deviation might go undetected by the customer — but at OTOMON, even a small deviation is unacceptable. A product must first be technically correct. Only then can voicing begin, refining the sound to meet the customer's ideal. Specifications may not be the deciding factor — but they are a prerequisite for building something truly good. WRONG BY A LITTLE AND WRONG BY A LOT ARE THE SAME THING. BOTH ARE WRONG.

04 — 革新

Innovation

When something has existed for over a century, it has been explored and refined toward optimum — but that does not mean nothing remains to be discovered. We do not only study what history has given us; we always seek what is new. Our O.U.D.D.C circuit, registered as a patent, is proof of this: we respect what previous generations have built, while never ceasing to search for better technical solutions.

05 — 無帰還は帰還より良い

Does Negative Feedback Kill Musicality?

Not necessarily.
In 1978, through mathematical analysis and measurement, it was demonstrated that negative feedback does not merely alter a device's harmonic distortion — it changes the original harmonic spectrum of the signal itself, and therefore the musical character of the recording. This is why many audiophiles prefer amplifiers with zero NFB. The observation is correct in most, but not all, cases. In over 80% of OTOMON designs we do not use feedback. However, in select cases, a very small amount of NFB — less than 5 dB, barely measurable — achieves something remarkable: a more controlled bass response and richer musical character. Whether to use it, and how much, is calculated with great care. Excessive NFB is a double-edged sword: it produces impressive numbers while eroding the very quality we are trying to preserve. In any OTOMON amplifier, if feedback is present, its purpose is never to improve the specifications — it is there to make the music more beautiful.

06 — SEはPPより音楽性が良い

Is Push-Pull always better than Single-Ended?

This is incorrect.
Since the 1930s and 40s — in RCA documents, the Radiotron Designer's Handbook, and later in the Journal of the Audio Engineering Society (JAES) — it has been proven mathematically that in a perfectly balanced push-pull configuration, even-order harmonics (2nd, 4th, 6th…) cancel at the output transformer. What remains are odd harmonics (3rd, 5th…), which tend to produce a harsh, cold character. These odd harmonics add vectorially to the original harmonic spectrum, shifting its balance and making music sound edgy or brittle. This bias has led many audiophiles to distrust push-pull designs. It is a serious misunderstanding. In a well-designed, intentional amplifier, odd-order distortion can be reduced or eliminated to the point where — even if it is present by the nature of the topology — it is too small to meaningfully alter your perception of the music.

会社概要 — About

About OTOMON

Founded

2009

Headquarters

Kanagawa, Japan

Founder

Ken Uesugi

OTOMON is composed of two kanji characters: OTO (音) — sound, and MON (門) — gate. Look closely at the company logo and you will find both characters interwoven. The English name Sound Gate is a direct translation.

OTOMON aspires to be a gateway — one that, when crossed, leads you into a world of sound that is entirely new: distinctive, alive, and full of energy.

Our core business is the design, manufacture and supply of hi-end audio equipment using vacuum tubes, as well as the repair and refinement of analog equipment. Every product is designed and built in Japan. All service and warranty work is also carried out in Japan.

"OTOMON is where we are obsessively meticulous in achieving maximum customer satisfaction with every product."

The meaning inside Logo

Look closely at our logo and you will find more than a symbol — you will find a world. The character at the top is 音 (OTO) — sound. The structure below mirrors the character 門 (MON) — gate. Hidden within the same mark, you can trace the Latin letters O, T, M, and N. Together, they become OTOMON.

In Japanese, when you place the word OTO (sound) inside the word MON (gate), it forms 闇 — YAMI — meaning darkness, the abyss, the underworld. Yet at the very heart of our logo burns a red circle, radiant as the sun. Light against darkness. Heaven against the void.
MON means gate. It also means boundary — the line that separates two worlds. In our logo, that boundary is drawn between the light and the dark, and sound stands firmly on the side of light. It calls to mind the Phantom of the Opera: music dwelling in the heaven above, and the cold silence of everything it leaves behind. That is why our website is black.
We named ourselves OTOMON because we believe sound is a gateway. Step through it, and the world is never quite the same again.

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