Japanese culture differ a lot compared to the typical western modus operandi.Its something that has fascinated me from my early age. There is something utterly different in the way they perceive the world and its mechanics and even more intriguingly how they act accordingly to their cultural and industrial standards. 

After my early discovering of the high-end audio creations by some of the most iconic Japanese high-end audio designers, my long and never-ending exploration began.

I’ve owned many of the electronic components from the Land Of The Rising Sun over the years, each very distinctive and unique in its own way. There was some universal unifying logic connecting them all with a hidden, underlaying sonic DNA common to all of them. I would’t exactly call it a warmish and mid range opulent per se signature. I’ve encountered of quite few gems, that completely stood out of any labeling. Still, there is indeed some invisible tread, that somehow connected them all with certain recognizing attributes.

So, when the opportunity arisen to try out one of the Shigeki Yamamoto’s Yamamoto Sound Craft Corpopration creations, I’ve had no second guesses. 


Trust me official web photos and uncle Google library won’t do the justice to the Yamamamoto A03S aura. The seamless blend of champagne anodized aluminum case and solid red cheery wood embodies the Japanese spirit with an captivating, minimalistic, yer luxurious aesthetic form, that is recognized even with the casual visual glance.

Yamamoto A03S KT88/6550 direct coupled single stereo power amplifier comes as a highly efficient amplifier in the beautiful form with a generous output power! Both KT-88 and 6550 based tube amplifiers are usually designed around push - pull principle. There are much less single tube based amplifiers on the market and this was one of the reasons for the Yamamoto A03 creation. 

Shigeki Yamamoto wanted to design an higher powered amplifier with more affordable power tubes like KT-88 and 6550, that are widely produced. Usual triode tube amplifier needs the high voltage to produce big power and with such particular design the cost of the amplifier automatically rise. 

With Yamamoto A-03S tube power amplifier high output comes from separating the plate circuit and screen grid circuit of an output tube. A-03S uses few of already proven and established circuit designs, that ensured the stable operation and great sound as well as more entry level pricing, yet still, all the electronic parts are of higher grade like Dale resistors, pure copper speaker binding posts etc. 

A03S uses two 5U4G rectifier tubes for the output stage, that supplies high current for KT-88/6550 efficiently, making para-sumptuous connection with both of the tubes.  

Further on 1D5G tube adopts a constant current ignition system and stabilizes the bias voltage of an output tube by constant -current, that also include the cathode bias resistance. 

It’s always said how amplifier is only as good as its power supply. All the energy and power is coming from there and if this portion is neglected one can forget about a good sound.

The quality of the tube amplifier is bound to both power and output transformers. Yamamoto A03S power amplifier adopts exotic material for the output transformer core and special Teflon insulating paper with the winding part. 

Beautiful chassis offers more then meet the eye. A03S enclosure is made out of solid wooden frame and aluminum parts and design in such way, that deals with the hubris of magnetic distortion.


Yamamoto A-03S tube power amplifier adopts the direct heating type pentode as a driver tube, that is connected to a very clear, direct and realistic sonic potency.

With the combination of the tubes and circuits Shigeki Yamamoto aimed for transparent sound that can handle fast attacks and dynamic shifts. Interestingly, the driver tube and the output tubes are linked directly, thus in absence of coupling capacitor  sonic imprint.

When pentode tube operate in its given role, sound quality is directly tied to power supply supply of a screen grid circuit, thus all the tubes can become independent and act stabilized.

The Yamamoto A03S ability to render the speed of the music properly and handle the attack responses is gained by stabilizing a screen grid circuit and by low impedance power supply supply. 

This is part explanation of Yamamoto’s original circuits and a reason of the A03S  balanced and stand out sound. 


Everything connected with Yamamoto A-03S is straightforward and simple. Even bias (current) setting for both left and right tube is no brainer, but it needs a shot peek into the manual, just to learn the optimum settings. 

The recommended value is between 90-110, but I’ve found using it most of the time at 100 mark. Do note, that on each turning on you’ll have to re-check the bias settings. They might drift a bit (plus/minus), but its good to keep it at the same level. This procedure takes only 30 sec and then you can rest assured as the value stay more or less at the same setting during the operation. 

Back side of the top cover is reserved for the signal inputs and outputs, and for the speakers’ binding post. All the connections are of vertical nature, that its even more convenient in some situations. 

Yamamoto allows an easy swap/tuber rolling with KT-88 as current meters on the top plate allows easy adjustment. Tungsol 6550 are factory installed, but KT88 output tubes were also part of the package. 

Both 6440 and KT88 offers more then subtle shift in sonic nature, but in my particular setup I’ve preferred Tungsol 6550 tubes. 


I've been around for long enough to draw some conclusions or at least to play bold in the game predetermination.

Yet, with more time and experiences, it became clear, that not everything can be predictable and ready to go under certain label.

Generally, as mentioned in the first paragraphs, I could go out and say how there's a typical Japanese sound DNA across all the tube power amplifiers that are coming from the land of the rising sun. In reality, this holds up to a certain degree, with few formidable exclusions. 

Back in time I've would drool and shake at each opportunity, when for example Kondo or Shindo gear came into the listening spotlight. These day I'm more interested in actual performance and factual sound. I'm still excited about the legendary exotic names, but just getting more objective and critical. 

System approach plays the crucial role in connecting any new component and as exotic or high praised it might be, without a proper synergy there is no sense of drawing hard fact conclusions. That's why it's more then obvious for a reviewers to have a wider variety of the gear to matched certain situation. 


Yamamoto A03S has proven to be a capable performer across all the genres, but particularly with smaller bands or ensembles, the unique ability of stand out realism came as forte. Three dimensionally and realists soundstage, as well as relief layering of the depth was evident regardless of the type of music. 

Karate - A new Jerusalem

This is one of the tracks, that continuously impresses my friends, when they’re visiting. Its one of the less forgiving songs, that can bring power amplifier instantly to its knees.

12 Watts per channel magic!? No way! Well, those were my thoughts exactly. But… Yamamoto A03S produced Thor like hammering toms and kick drum fast transients with authority and sharp attacks. 

How’s that possible? Usually, the secret is in the output transformers, but as described above with A03S the powerful and controlled output is closely connected with specific circuits and powers supply. 

My Mactone tube power amplifier uses two 300B tubes in parallel with 24 Watts per channel, but comes no where near of the Yamamoto A03s power output and sense of control. The instant lock and load of Yamamoto A03S is something to experience. Its not only about sheer power, but about the ability to form a believable, gut feeling energy transfer.  

Mika Sasaki - Obsidian

Realistic piano recording, that embraces all the blows and whistles is not such an often occurrent despite so many glorification. In reality, many have their own idea of how piano should sound and not how actually sound. You can find the balancing act here and there, but somehow we’re always striving for more of complete realism. 

Mika Sasaki’s Obsidian, the album offers a refreshing density of spatial and acoustical cues, that makes this record both very different and charged with great portion of realism. 

Yamamoto A03S managed to render spectral acoustical shadings with unique resolving nature, that more then surprisingly lurked into the world of reality. 

Density of piano overtones and acoustical focus points managed to recreate Mika’s performance with captivating realism and highly involving factor. This is something, that is usually connected only with the performance of uber amplifiers. The drama would sum up the Yamamoto particular attribute, that was of unexpected proportions. Musical drama is closely connected with believability factor, that forms one of the ground stones of realistic illusion. Taking experience to such level at this price is something needed to be spotlighted.   

Al Di Meola - Sarabande from Violin Sontata in B minor  

Surely not a typical song one would expect from Al Di Meola. Anyhow,  its always among my reference tracks for many of the reasons. The feather like rendition and almost blossomy guitar playing encapsulate emotionally charged performance, that calls for wholesome and energetic amplifier’s hearth. To cut into the Sarabande’s inner core, power amplifier needs to de-mask many of the typical-filtering layers. For some reason tube based amplifiers excel at this particular role, but there is a very narrow line between balanced and accented-over-saturated act. 

Yamamoto A03S has shown its real nature and DNA through rendition of copious harmonic guitar notes structure and not detached reality as with many of the tube amplifiers. A03S formed a performance of both emotional and realism bound. 


I can certainly call the Yamamoto A-03S a surprise of the year. Little I was expecting, that such a stand out performance, especially related with the drama and realism, would be of proportions, that are even hard to find in more exclusive and heftier priced amplifiers. 

Experience of three dimensionality and sense of musicians being there still lingers with me. We’re often talking about a lot of audiophile qualities connected with the sound, but perhaps we forget about one of the major and key factor intimately tied with the grand illusion. The realism! In its absence  reproduction merely feels like early versions of digital pianos; a wash out wanna be. The sound might had a spot on timbre and tone, but it lacked the spatial information, that would make it believable. And, this is exactly where Yamamoto A-03S strikes in. The believability.

I’m yet to come across the amplifier anywhere near the Yamamoto A03S price point with this particular quality being so captivating. At one point, my good friend that I’ve trust on the critical listening part visited me and I’ve silently waited for his response, while playing some music for him. The response was similar to mine. Oh my….!#”=??*?

Once you’re used to the sound and even more to the feeling of the live music as well as energy related with the real instruments being played, its hard to cope with lower lever of illusory inputs. Similar to the great food, wine and spirits. There’s no turning back once you climb up on the upper echelon ladder. 

Yamamoto A-03S tube power amplifier shifted my perspective of the “traditional” Japanese tube power amplifiers. It does come from the similar school, but it also comes with the set of rules, that have opened a new chapter in by book of audio.  

A-03S do need proper-matching preamplifier and it found great synergy with my Robert Koda Takumi K-10 preamplifier. I only wish I’ve had it long enough around to try with my latest addition to the reference system - The Bespoke Audio Company Ultimate Silver Preamplifier. Well don’t want to sound predictable, but it might even more microscopic evaluation of the layers.

Yamamoto A03S fervent dedication is with music first. The ability to shift reality into a much grander illusion then expected dangerously steps into the realms of the big boys. The most interesting and inspiring part of the Yamamoto experience comes in a form of factual sonic result. Having such abundance of upper echelon attributes, although in particular regard is something I would never come across at this price level. 

Yet, its 21st century and as proven so many times in the past, one need to be an open book. Elitism, guru mentality and ego tripping is non rewarding for both audio reviewer and any publications’ audience. 

I’m glad I’ve taken the opportunity and evaluate Shigeki Yamamoto golden creation. It actually feels great to be corrected once and step out of virtual precognitions. 

Yamamoto A03S tube power amplifiers is open to sonic ambiguity, while still keeping its own pace. In the world of so many déjà vu tube amplifiers, Yamamoto San represent a proud example of pushing the boundaries of the expected sound. 

Yamamoto A03S is exotic high-end audio creation without forcefully trying to take such role. The combination of unique power supply, tube implementation and “voicing” brings something utterly refreshing and potent. The perceived resolution 

colors and shadings of musical reality are freest in form. The experience it comes with A03S is far from being only sublime. Its acting closer to the constitutional reality check points!

Most importantly, it revived my interest in low powered tube power amplifiers. 

For what it represent and at what price point Yamamoto A03S deserved to be highlighted. I’m happily giving out the Mono and Stereo Highly Recommended Award.  

Matej Isak

Website: link .




Model: KT-88 / 6550 single stereo power amplifier
Tubes: KT88 or 6550 2 pcs. 1D5GP 2 pcs. and 5U4G 2 pcs.,  standard output tube is Tungsol 6550.
Maximum output: 2x 12W
Frequency range: 25 to 50 kHz
Input impedance: 200k ohms
Dimension: 460(W) x342(D) x190 (H)
Weight: 18kg


Shigeki Yamamoto
Yamamoto Sound Craft Corp.
726 Sakaki tyo
Ono city
675-1323 Japan