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Seeing how SPEC have four different integrated amplifier models—the RSA-717EX, F3EX, M3EX and V1EX—but little to distinguish them to the naked eye (the 717EX is smallest as the next photo shows on the top left-most rack), I asked Yoshi Hontani, English-speaking Japanese audio exporter for SPEC and other Japanese brands like Leben Hifi, to talk me through their specifics on behalf of Shirokazu Yazaki.
Munich HighEnd 2013 left side wall SPEC electronics display
"We think of the M3EX as our main export model. It’s very important for us and thus much improved over the domestic M1 version. To clarify the differences between RSA-F3EX and M3EX, I should first point at their commonalities. The class-D amplifier module with IR output devices and R-core power transformer are exactly the same. Hence the power and sonic structure are the same too. But certain parts in the power supply, low pass filter and snubber circuit differ. And it is these differences which determine the particular sonic character of the F3EX and M3EX. In the M3EX power supply we changed the rectifier diode from an ultra-fast soft recovery type to the very latest SiC (silicon carbide) Schottky.


"This SiC diode was first introduced last fall by ROHM, a semiconductor maker in Japan. We made our selection only after hearing 10 different types of SiC diodes during a ROHM presentation. As a result the winning unit has very powerful high-speed bass and a completely noise-free treble. Simultaneously we also evaluated high-capacity industrial soft-recovery versions used in the F1 and F3EX which are very detailed nuanced and rich.


"I felt that the sound of this diode performed much like a high-quality tube rectifier. At present I thus couldn't decide which was the better diode - the one in the M3EX or F3EX. The amps' actual sound character is directly related to this choice of diode. Both also adopt the Arizona Capacitors Inc hermetic-seal oil-filled caps and custom mica caps in their low-pass and snubber circuits. Because we developed a very close working relationship with this company for the last three years, we have access to two types of custom oil-filled caps. Our REQ-STEX phono preamplifier uses both of them. For our power amps we use the C85805 for the F3EX and the C30509 and C85805 for the M3EX. The F3EX connects two half-size caps in parallel in both the low-pass and snubber circuits to pare down equivalent series resistance. The M3EX uses the C50309 in the low-pass filter and the C85805 in the snubber circuit. Thus the sonic differences between these amps also relate a bit to this choice of capacitor. I myself have many experiences with many kinds of mil-spec vintage oil-filled caps. This eventually led to us Arizona Cap. not only for the low-pass filters, snubber circuits and power supplies of our class D amps but also for our speaker-impedance compensator boxes RSP-301 and 501EX. And I use Arizona caps in my old valve amplifiers coupling their driver and output tubes and in their power supplies.
M3EX oil-filled capacitor
"So I listen to music with Arizona caps every day at the office and in my home. I thus have some very specific opinions about their sound. The C85805 is a KP/AL/mineral-oil part, the C30509 a KP/MY/AL/mineral-oil type. Our chief engineer Mr. Banno and I appreciate and love them both. The C85805 has an extremely beautiful saturated midrange and treble to be perfectly matched to female vocals and stringed instruments like the violin. The sound is very graceful and pure. This comes from genuine-pulp Kraft paper dielectric. It's a material very close to nature and sounds sweet. The dielectric for the C30509 adds Mylar film. Its sound is almost perfectly balanced top to bottom but the most spectacular registers are the lower ones. Compared to the old vintage West Cap style this sound has better bass speed and a smoother treble to better fit today's broader bandwidth high-resolution music. Yet it retains the desirable warm vintage color of famous US caps like the Sprague 'Bumble Bee', 'Black Cat' and 'Vitamin Q'. I became convinced that the C30509 is the true successor to the famous West Cap vintage capacitors made in the US. I thus decided to distribute these caps in Japan for our domestic valve-amp fans in the summer of 2011. It took time but the name Arizona Capacitors has gradually become very familiar to Japanese DIYers. The common virtue of both types of Arizona caps is their extraordinarily natural sweet sound which gets even more so over prolonged use. Above all it's evidence of the real thing from my personal view on hifi parts.
Munich HighEnd 2013 front wall with Amphion speakers from Finland
"I should return to the sonic character we aimed for with the RSA-F3EX and M3EX which reflects the C85805 and C30509 capacitors. There also are the mica caps whose sound our catalog describes 'as transparent as a blue sky'. I feel that mica caps have the best reliability and HF performance. So it becomes the combination of our custom oil-filled and mica caps which exceeds the performance of any other type of signal-path cap I'm aware of. In the end it's this very strategic very well-researched combination of parts which defines our amplifier sound and especially the F3EX and M3EX models. Mechanically our RSA-F3EX as the top model also gets heavier aluminium panels which directly reflects in its higher price. Here we also added very special electrolytics to the power supply. Like magic this vastly improved ambient retrieval over the F1. The M3EX meanwhile benefits from the SiC rectifier to enrich its already powerful sound across the entire range. If one proposed two sides of the true meaning of enjoying the music, one would be delight, the other healing. In this sense the RSA-M3EX would be delight whilst the RSA-F3EX's tone would have some healing effects."


So we have it in writing. Even its own designer doesn't consider the RSA-M3EX to be just neutral. For that he offers the more affordable V1EX.
RSA-717EX
What's wrong with just neutral? Wrong question. The V1EX covers that base. It'd be better to ask why Yazaki-San might hold a different personal preference; and why he believes others might join him in that costlier choice. For probable cause we refer back to an interview we published in a previous review of SPEC's phono stage. "Around the end of the 1990s and by the beginning of the millennium, Pioneer had reached its zenith. Our engineering team enjoyed the rare opportunity to develop as high-end a DVD player as the AX10. We also had a well-designed spacious listening room. We could select high-priced speakers, preamps and power amplifiers to be our reference for the development of the AX10. I remember that I bought a pair of B&W 801 which then was the reference of specialist audio shops in Japan. Of course B&W 801 were always driven by high-power semiconductor amplifiers of various famous domestic and foreign brands. Yet Mr. Banno and I were never moved by the sound of this high-end audio system. The sound was like watching miniature paintings. We could hear all the details but were never touched by the music. We felt that the sound was very precise but one-dimensional. It lacked any real dynamics and rhythm. When I returned home and listened to music over my old high-efficiency system, I was once again intoxicated by the playback which was so transparent, natural and organic. I felt that the difference came from the distinction of certain dynamic characteristics between these two systems, not merely specific static qualities."


In a later manifesto, Shirokazu put it this way: "With the mainstream of recent efforts pursuing audio quality based on the combination of low-efficiency speakers and high-power transistor amplifiers, what's really possible is merely a sound that expands on or behind the plane of the speakers by emphasizing a feeling of elaborateness, wide frequency response and a rather thin tonal quality. Even if such a sound presents a high degree of perfection from the point of view of audio measurements, does it really bring us the joy and excitement of music?"

Shirokazu is far from alone questioning whether modern hifi hasn't made a bad turn somewhere to keep heading in the wrong direction. Zu's Sean Casey has long been on record on the same matter. So have various others. They all believe that in the pursuit of extreme resolution and parallel demands for ever smaller speakers of increased loudness and bass capabilities, something vital was lost. This view doesn't sugarcoat the fact that Western Electric-day systems had limited bandwidth and high distortion. It's not about returning to 50Hz-15kHz-3dB bandwidth and with it a wholesale elimination of modern music anchored in low bass. It's about maintaining legitimate gains made since whilst recovering aspects of valve tone and the easeful dynamics of vintage high-efficiency hornspeakers they feel have been sacrificed or diluted.
Over the RSA-717EX features, the M3EX adds defeatable volume-control backlighting and amp-direct mode
Means. Motive. Opportunity. SPEC's solution bypasses the SET/horn revival which in Japan remains very active. They pursue conventional dynamic speakers of ±88dB efficiency to make a similar type of sound. For said purposes they harness the very latest in analog switching technology. That's admittedly somewhat radical. It's also quite in contrast again to our earlier mentioned Bruno Putzeys who applies very advanced math and error correction to obtain measurable neutrality and ultra-low distortion. SPEC actually treat their class D amps as valve circuits. They merely swap output devices. Tubes out, DirectFets in. That grossly oversimplifies things but points straight at the heart of the matter. A minor rebellion like Xalapas' El Candigato? Given the strategic component allocations hinted at above, should we assume that what primarily distinguishes the various SPEC amplifiers is different voicing? Shirokazu after all knows exactly how each part of their circuit contributes to the final sound and what to specifically change if one meant to shift sonics in a particular direction.

"The first SPEC model was the RSA-F1. It implemented our full technology with the highest-grade parts and components without regard to production cost. Based on this model we further improved the export version RSA-F3EX mainly by upgrading core power supply components. This made the sound even more graceful and sophisticated. Our second model became the RSA-V1 where intent was to reduce build cost with more affordable parts. The export version V1EX upgraded some of those again. The RSA-M1 was tuned specifically for JBL and Jazz lovers to increase dynamics in the mid to low registers and make the sound more active. The M1EX export version was further improved to cope with all manner of musical categories whilst maintaining the original sound signature.The RSA-717EX is a recent development to undercut the price of even the V1EX by applying a switch-mode power supply. This achieves similar sound to the RSA-V1EX and perhaps is superior for certain music.

The M3EX differs visually from the V1EsX with two larger capacitors whilst certain parts underneath the shielded cases are different. The PMW switching modules of the M3EX and F3EX are the same to generate identical 120wpc/4ohm output.
"Although the difference between F3EX and V1EX isn't double, the F3EX is the ultimate expression of our technology as implemented with the very best parts possible. Given this, if I had sufficient money to buy an F3EX, I might chose the F3EX over the M3EX to get the best even if I couldn't distinguish a clear sonic difference. If I couldn't afford the F3EX, I might convince myself that the M3EX was better for my favored music or that the difference was insufficient to pay double. We consider the V1EX our entry-level model. People who don't care about its SMPS will instead go for the 717EX whose sound exceeded our own expectations for it. In conclusion there are clear sonic differences between our three models (the 717EX is an exception). One final advantage of our amps are their superior linear power supplies. They convert over 95% of the wall power into actual output power. Usual transistor amps manage only about a 25% conversion margin. From this follows that our amps drive speakers three times as power hungry as our raw specs would suggest."


The published power ratings for the RSA-717EX/V1EX are 50/100wpc into 8/4Ω and 60/120wpc for the RSA-M3EX/F3EX. Following SPEC's math one should consider them actual 150/300wpc and 180/360wpc ratings versus conventional class A and A/B amps. Surprising perhaps in the maker's descriptions about their lineup is specific voicing, sometimes even for specific speaker brands or music styles; better export than domestic versions; and implied superiority of linear over switching power supplies even though the model with the SMPS is called "perhaps better for certain music" over its equivalent with the linear supply. Either these lines are blurrier and more ambiguous than good/better/best ideologies would wish; or like any loving parent Yazaki-San felt hard-pressed to be too specific about classifying his offspring. On price tiers SPEC hadn't officially begun exporting all models but tentative projections anticipate €18.000/$24.000 for the RSA-F3EX i.e. twice our review model; and €7.2000|$9.500 for the RSA-V1EX.
ultra-fast soft recovery diodes of the F3EX