I’m sure that many of you have in one way or another already heard about the SPEC Corporation, that was established in 2010. Their distinctive looks, very unique implementation of technology and materials let many wonder how these amplifiers really behave and stand in the real world scenario. 

There are many manufacturers that are trying to push-forward the Class D technology in many a variety of ways with an incremental variable of positive outcomes. Those of you who’ve been following me for a bit more time knows, that I’m not really a big fan of Class D based amplifiers. While I’m all about the greener side of electronics, so far I was always left cold with most if not all of the Class D offerings.

But as always, I stand to be corrected and I’m an open book when it comes to the new products and approaches. Yoshi Hontani has presented a lengthy and intriguing introduction about the SPEC Corporation RSA-M99 integrated amplifier to get me hooked and as you can read on this amp is not only very unconventional but also highly musical for Class D. 
This is certainly due to the SPEC Corporation research in the latest Class D solutions. They’ve heavily researched and dig deeper into dramatic speakers drive power as well as the advanced energy-saving performance.
The result is an intriguingly tone opulent sounding amplifier that can deliver a mighty dynamic impact with some of the qualities one would never associate with the Class D. 


The SPEC Corporation amplifier concepts’ core original idea reflects the musical instruments. SPEC Corporation strongly believe how the combination of different woods in combination with the chassis leads to the beautiful and genuine sound, that mirrors the essence of music instrument.

For this reason, the complete bottom surface is hosting a massive, solid spruce board. Spruce is known to be used for some of the most cherished violins and SPEC Corporation is implementing it to achieve the harmonically rich density. 
This particular tuning and dealing with the micro resonances and vibrations are further explored with the maple feet, that have the hickory embedded in the center. Interestingly, only the hickory located in the middle is grounded. 
This wooden soundboard and feet were designed to vibrate and affect the audio signal, hence providing a natural sound.


If you thought that we’re done with voicing, here is another tuning part that SPEC Corporation puts a lot of attention. 
By blending various capacitors their goal was the reproduction of highly sophisticated and expressive sound.

In collaboration with world-renowned capacitor manufacturer “NICHICON,” they’ve developed the “HIBIKI-ICHI” with a clear master plan of ensuring a lighting fast response and natural tone. From the very beginning, the “HIBIKI-ICHI” was envisioned to convey even more dense texture, translating to a more musical sound.
You can spot a JAPANESE KANJI letters written on the surface of the capacitors. This KANJI is pronounced as “HIBIKI-ICHI”, and ‘’HIBIKI” means vibrancy.


Another important part of the SPEC Corporation RSA-M99 integrated amplifier is the R-core transformer. This transformer is a key point of presenting the dynamic and powerful sound and it’s used in the top of the range models. 


The R-core transformer and other components are separated by the modular structured shieldings. In addition, EMC coating is applied to the inner surface of the chassis, reducing internal electromagnetic noise.


So-called High driving ability is an essential part of SPEC REAL SOUND. In order to reproduce the sound with distinctive musicality the amp’s ability to properly drive speakers is of utmost importance. 
SPEC Corporation see the ability to drive and stop the speaker instantaneously as one of the crucial parts of the amplifier potency. 
SPEC Corporation has incorporated the “Class D ” and found it as the technology that can achieve the extremely potent lock and load with the speakers, thus reproducing the musicality of live performance with a necessary impact. 
With RSA-M99’s PWM system at the front of the “CLASS D” block, the PWM system’s analog heart was designed to amplify the very fragile signal without losses. SPEC Corporation firstly believes that a pleasing and articulated sound can only be achieved by the unaltered amplifying of the minuscule signals.


As a cherry on the top of the cake, the overall aesthetic aura is also connected with the mesmerizing yellowish light rings emitting the two of the main knobs. The already zen-like balance is cleverly enriched with soothing and relaxing light ambiance.


The SPEC Corporation RSA-M99 integrated amplifier’s volume control has proven to be something special. The volume/gain is executed via 0.5dB x 256 steps attenuation.

The volume control knob on the front panel is not an encoder,  but a mechanical volume. The audio signal does not pass through the volume itself. By turning the volume up and down the 0V-5V DC voltage is generated and change the attenuation level in the “MUX” block.
The separately sold remote control (external box) does put another DC voltage on this stage. 
Internally the remote control uses a microcomputer which generates a clock, therefore, SPEC Corporation has employed an external remote volume to remove the noise source from the amplifier. In the future SPEC Corporation might consider the internal volume to comply with requirements of the one-box design. 
I have to applaud how well the SPEC Corporation RSA-M99 integrated amplifier’s volume part is implemented. The gain quality itself deserves high praise alone and it’s one of the RSA-M99 prominent features. 


SPEC Corporation RSA-M99 can be used both integrated or power amplifier. When it’s set to POWER AMP mode, the volume level becomes fixed at around 20dB regardless of the volume knob position. In the integrated mode, the volume is operated via the knob turning or with the additional remote (not supplied for the review). When VOL. LED/MODE switch is set to POWER AMP., the VOLUME (level adjustment knob) and the LINE SELECTOR (input switching knob) brightness is set only to OFF (no light).
RSA-M99 is easy to handle and everything is very straight forward. The two large and beautifully crafted knobs on the front panel offer the volume an input selection. On the right side, a large power switch needs to pulled out to releases the lock and to put the amp into the operation. Input selection is as simple and straightforward. 
On the far right side, the AC IEC connector shares the space with remote control input and the fuse. A bit closer to the right is VOL. LED/MODE switch changes the volume and line sector rings brightness. It’s set to the light on by default at the time of purchase.
In the middle, there are speakers binding posts and the right side is reserved for the five inputs. Three RCA inputs and two balanced.
Everything is laid out logical and with enough space to easily connect the needed cabling. 


The first album I wanted to hear with the SPEC Corporation RSA-M99 integrated amplifier in action was Kenny Burrell – Midnight Blue (The Rudy Van Gelder Edition). The whole album is harmonically enriched, but particularly the “Soul Lament” (my favorite track on the album) is an epitome of tone, timbre and color congestion. 
The captivating spirit of Burrell’s playing is breathtaking and it really calls for a more stalwart amp’s core to fully bloom. To my big surprise, RSA-M99 has managed to incorporate an unexpected level of tone copiousness. While simplistic at glance, “Soul Lament” tones’ overlays do present a genuine challenge and  SPEC Corporation RSA-M99 revealed the timbre and tone quality, that is usually reserved for any other technology than Class D. 
Steely Dan’s Two Against Nature introduces a different kind of difficulties. “Two Against Nature” demands a fast, energetic amplifier with the step-forward dynamic ability.  RSA-M99 mighty hearth allowed instantaneous expansion of Steely Dan’s complex arrangments. A healthy dosage of power is needed for  “Two Against Nature” to unfold completely,  but it’s not a key point. The magic is in the proper storage and deliverance of the current and SPEC Corporation can submit a plethora of upper-level music’ momentum.
This was confirmed with the oddly demanding Alarm Will Sound’s album Acoustica. These renditions of legendary techno genius Ricard D. James aka Aphex Twin are utmost challenging and  “Blue Calx (arr. C. Burhans)” belongs to the heavy-duty league tracks on the album. Not only for the sheer stamina delivery (which is crucial). The amplifier needs to equitably distribute the needed force, but not on the account of preventing the subtleness to develop. 
RSA-M99 was not conquered by “Blue Calx” necessitating requirements. Along with evenly distributed energy the level of detail provided by this Japanese integrated amplifier has raised the bar of what it’s expected from the Class D tech.  
I wanted to further explore the delicacy and amp’s vitality with Herbert Joos – The Philosophy Of The Fluegelhorn. The album’s opening track “The Philosophy Of The Fluegelhorn” represents a loupe like striking sonic scape that not only exceeds the usual room dependency,  the augmentation requests a substantial force formation to truly disappear into and through the walls. 
Again… The SPEC Corporation integrated’s vehemence was impressive and so was spatial distribution.   
RSA-M99 provided great spatial attention and that was readily apparent with Daniele Di Bonaventura, Paolo Fresu – Altissima Luce “Altissima luce col grande splendore”. 
When spatial orientation is to converge on the particular attribute this is a clear sign that something went south. On the contrary, the RSA-M99 has shown unexpected spatial unmasking, that is descriptionally more the in the domain of either Class A or Class A/B amplifiers. 
It was interesting to observe RSA-M99’s segregation capability without losing its harmonic core. With  “Altissima luce col grande splendore” SPEC’s amp didn’t reduce the amount of momentum received from the source and has succeeded to contain both voices and atmospheric solidness. 
I’ve further investigated the vocals’ velocity, but this time in a sole domain. Cassandra Wilson’s –New Moon Daughter “Strange Fruit” is one of the songs that permits the more insightful observation of the harmonicity. SPEC Corporation have already shown a great ability to convery complex harmonic tones with multiple voices where despite consisting of various singular voices they’re are and should be perceived as a coherent whole. 
RSA-M99 has confirmed to be an adept performer also with a single voice,  where differences in fundamental frequency can be easily spotted and they’re much more vivid to attest. 
All of these aspects might sound a bit technical, yet they closely correlate with the absolute consonant vibrancy. And that’s not all. 
The additional measure needed to be met for the true high-end designation is an interactive act. Such interaction should come from within the amplifier core and not exogenously. While studio recordings can water down some of the intimate correlation, the live acoustical recordings are less adept to this recording circumstances.  
SPEC Corporation RSA-M99 integrated amplifier’ auditory stimuli allotted a splendid interaction, pushing the RSA-M99 into the areas that are not even remotely expected!


The term “voicing” is not usually correlated with the amplifiers for plentiful of the reasons. Many of the high-end audio designers almost fanatically and by all means try to alienate themselves farther away from any association with the word voicing. 
In reality, every amplifier final sonic output is like it on or not subordinate to the tuning. An amplifier is more than a sum of its parts. It closely reflects the mind and choices of the audio designer.  There is no high-end audio electronic component, that can be termed as ultimately transparent. At least yours truly didn’t stumble upon it yet. 
Yes, there are different explorations of contrasting audio characteristics, but even on the opposite sides, the sonic tint can always be identified with some recognizing sound characteristic. This is why the assembly of a great-sounding high-end audio system is an art of its own. There is no blacks and whites when it comes to the fruitful coupling of diverse components into the supremely sounding upper echelon set-up. 

The adventuresome audiophile and music lover are challenged with quite a struggling journey for balancing act. As many of you know for fact it might take years to accomplish such an intense assignment. 
By no means, I would call the SPEC Corporation RSA-M99 integrated amplifier a typical sounding Class D amp. It dissents the common criteria in every way. The above-mentioned design decisions by default points towards something very unconventional and RSA-M99 doesn’t sound like typical amplifier nor looks like one. 
I like how far the SPEC Corporation has pushed its concept. This is the determination that differentiates Japanese made products from the rest of the crowd. 
As proven over the decades, the opulent heritage of the Japanese way of doing things allows them to look outside of the box and following the non-ordinary proceedings. 
They are not afraid to explore exotic approaches and materials. While the end results might not always be valid, the RSA-M99 is an exemplary product. This integrated amplifier from The Land of The Rising Sun that sticks out of the cliche and accouches an aural impact that is of stand-out qualities. 
In the search for an audio holly grail, even the techno purist are in one way or another searching for the music’s gist. The end goal is no different from the numerous paths that the high-end audio connoisseurs are willing to take. 
Setting the record straight, I’m not advocating any kind of saturation or sonic coloring. Yours truly is as many of you perpetually trying to discover for the harmonic focal-point. The very essence of the music.

While I’ve had some experience with SPEC Corporation products from various audio shows and events, I’ve surely didn’t expect such a musically rich discovery. But that’s not all. 
RSA-M99 delivers a surprisingly compelling impact, that feels to be of much higher output than its specified. Even with a complex orchestral music RSA-M99 doesn’t seem to be pushed into the corner. 
Not only sonically, but also a design-wise I truly relish the extra efforts that SPEC Corporation took with the accomplishing of the RSA-M99.
In the era of the aggressive market, every little thing counts and by each year more people are showing an interest in the distinctive characteristics. Of course, the sound reproduction quality is at forte. But… Amplifiers are the daily music machines and not a small amount of audiophiles and music lovers strive for the high style external appeal.
SPEC Corporation pounded with the RSA-M99 outlook. Combined with the unusually musical sounding potency the RSA-M99 deserves my recommendation. This integrated amplifier has changed firm convictions about the Class D. But that feature combined with the stylish looks, an impressive gain handling, and musicality grants the  SPEC Corporation RSA-M99 integrated amplifier the 2019 Mono and Stereo Highly Recommended Product Award!

Matej Isak


– 10.900 EUR


  • Maximum output: 120 W × 2 (4Ω)
  • Frequency response : 10 Hz – 30 kHz ±1dB (6Ω, 1W)
  • Harmonic distortion ratio: 0.02% (at 1 kHz, 80% output)
  • Input sensitivity, gain: 300 mVrms, 37.3 dB (at MAX volume, 6Ω, 1kHz, unbalanced input)
  • Line input terminals: XLR input: 2 RCA inputs: 3
  • Speaker terminal: 1

  • Electrical consumption: With no signal: 15 W, during maximum output: 215 W (8 Ω, 100 Hz)
  • External dimensions: 440 mm (width) × 125 mm (height) × 414 mm (depth)
  • Weight: 15.5 kg

Included items
  • Power cord 1
  • Operation manual 1

  • RSR-1 is sold separately 


TOKYO 103-0024
TEL +81-3-3660-0303 
FAX +81-3-3660-0333
E-mail: e-hontani@musonpro.com [exporter] Muson Project ,inc.