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Phono preamplifier
SPEC Corporation
Designer Audio REQ-S1 EX

Price (in Europe): 14 000 Euro

Manufacturer: SPEC Corporation

Contact: 6th Fl. Shin Kioi-Chobuilding ǀ 4-1 Kioi-Cho, Chiyoda-Ku Tokyo 102-0094 ǀ JAPAN
tel.:/fax: 03-6272-6011 | e-mail:

Manufacturer's website:

Country of origin: Japan

Product provided for testing by: MuSon Project

Text: Wojciech Pacuła | Photos: Wojciech Pacuła
Translation: Andrzej Dziadowiec

Published: 4. June 2013, No. 109

The whole story began over a year ago, when I was preparing materials for another, perhaps already seventh, annual "Japanese" issue of "High Fidelity" (all previous "High Fidelity" issues are available under the "Archive" tab). I asked for help Mr. Yoshi Hontai, of whom I had once written so there is no need to introduce him. Together with his son Elia, he made a few appointments for me with some completely unknown manufacturers from his home country, still full of secrets. This is how I came across products from Audio Replas, fo.Q, SAEC, Air Cable (Okutsu Denko Co.) and the first classic product from SPEC Corporation, the RSA-V1 amplifier (see HERE).
A few months after the review, I received a very nice letter from Mr. Shirokazu Yazaki, chief SPEC designer, in which he thanked me for accurate observations and shared his experiences. He also sent a brief report of a New Year's Eve meeting, during which together with his friends he auditioned his latest design – a tube amplifier of his own design, based on very exotic tubes from Western Electric that he made for his friend (see HERE.) Thus began our e-mail friendship. It is unusual to find a person separated from us by thousands of miles, from a completely different culture, with different professional experience, yet with whom we share a similar sensibility, similar tastes and views! After a while, an idea of a phono reference preamplifier began to crystallize:

I just written how was the New Year's party. I wish if you were there!!!
And one more information, we will release a new product, high quality phono-equalizer REQ-77S for our domestic market tomorrow. Please wait for the detail.

Let me show you some photos of our new product, REQ-77S. For European model, I would like to modify or improve the sound with more rich mid to low range from our domestic model. So the model number should be changed. Please look forward to hearing the sound of the phono-equalizer with very simple circuit and full of desirable parts.

We improved the sound of REQ-S1 compared to REQ-77S our domestic version because of the sensitive hearing of European people like you. I wish you could find and feel the performer's mind & soul with our S1. About our REQ-S1 I would like to make it clear that we adopted newest devices, ultra low noise and high gain operational amplifiers within very simple circuitry, but the circuit become more simple we are able to hear easily the differences of the passive parts, such as capacitor and resistor. And so we could find the best parts for our target. This fact is just same as our class-D amplifier and RSP-501EX. Put simply, the experiences of development, class-D amplifier and RSP-101, 301, 501EX led to REQ-S1.

Let me send you our brochure of REQ-S1EX. I suppose you could find another features of REQ-S1EX. About the power supply we adopted newest SIC (silicon carbide) diodes. These diodes, also used in RSA-M3EX at the same timing are free from switching noise and have the excellent sound character such as transparent mid to high end above all rich and powerful mid to low end.

Regards, Shirokazu Yazaki

The REQ-77S was launched for sale in Japan in March 2013, and its European version, the REQ-1S EX in April of this year. Our review unit comes with the serial number 0001, so we deal with the world premiere. It should be added that at Munich the manufacturer will show its new, mass loaded AP-5 turntable (we are the first to show its illustrations).

SPEC in “High Fidelity”
  • REVIEW: SPEC RSA-V1 – integrated amplifier, see HERE

    A selection of recordings used during auditions

    • Bill Evans, Selections from Live at Art D'Lugoff's Top Of The Gate, Resonance Records, HLT-8012, Limited Edition #270, blue vax 10” LP (2012).
    • Cannonball Adderley, Somethin’ Else, Blue Note/Analogue Productions, AP-81595, “The Blue Note Reissuses, 45 RPM Special Edition #2468”, 45 rpm, 180 g, 2 x LP (1958/2008).
    • Clifford Brown and Max Roach, Study In Brown, EmArcy/Universal Music Japan, UCJU-9072, 180 g LP (mono).
    • Depeche Mode, Delta Machine, Columbia, 460631, 180 g, 2 x LP (2013).
    • Eva Cassidy, Songbird, Blix Street Records/S&P Records, S&P-501, 180 g, LP (1998/2003).
    • Keith Jarrett, The Survivors’ Suite, ECM Records, ECM 1085, LP (1977).
    • OMD, Dazzle Ships, Virgin Records, 205 295-320, LP (1993).
    • Talk Talk, Spirit of Eden, Parlophone/EMI, PCSDX 105, 180 g LP + DVD 24/96 (1988/2012).
    • The Cure, Disintegration, Fiction Records, 532 456-3, 180 g, 2 x LP (1989/2010).
    • The Montgomery Brothers, Groove Yards, Riverside/Analogue Productions, AJAZ 9362, “Top 100 Fantasy 45 Series”, 45 rpm, 180 g, 2 x LP (1961/?).
    • Tingvall Trio, Skagerrak, Skip Records, SKL 9057-1, “Limited Edition”, 180 g, LP (2006).
    • Tommy Schneider & Friends, The Hidden Port, Kolibri Records, No. 12001, 180 g, LP (2012).
    • Wes Montgomery & Wynton Kelly Trio, Smokin’ At The Half Note, Verve/Universal Music K.K. [Japan], UCJU-9083, 180 g LP (1965/2007).
    • Yaz, Upstairs at Eric's, Warner Bros. Records/Mobile Fidelity, MOFI 1-020, "Silver Label", "Special Limited Edition No. 2044", 150 g LP (1982/2012).
    • Zakir Husain, Making Music, ECM 1349, LP (1987).

    Shirokazu Yazaki is a man who knows what he wants. He's an engineer, chief designer at SPEC Corporation and in his work he is guided by an ethos of logic he learnt (I assume) at college. However, unlike many of his colleagues, also in Europe, he is not its hostage. Or rather, he is guided by logic adapted to the conditions and the material he deals with. And that is MUSIC, which in turn requires thinking outside the box, going beyond the confines of academic knowledge, often quite dull, I must say, when it comes to coping with the things that are difficult to measure and that need to be worked out with the most sensitive instrument – human ear.
    In their pursuit of truth, a music truth or an internal logic of tracks played and listened to at home, the designers are doomed to working out compromises and making choices. This is how it was, it is and it will be – no inventions, technologies and techniques will change that. Mr. Yazaki knows this very well. I can hear it using his products, I can feel it listening with their help to music; I can hear and understand it. The reference sound for this Japanese designer are tube devices, including tubes from Western Electric – rather more exotic types, but also 300B. This is how he tunes his class D amplifiers and this is how he tuned the sound of the REQ-1S EX preamp.

    In absolute terms, if we were to distance ourselves for a while from the music and concentrate on the sound, its sound is quite warm, with limited selectivity. This is not a "tool" to analyze the recordings, various pressings or versions. Although it shows a lot of information, it does it "along the way"; all these elements are in the background. You can hear them, sometimes they even manifest themselves but they do not come to the foreground nor are even comparable to the main presentation.
    Example? - First that comes to mind: the preamp makes the recordings somewhat similar to each other by rounding the attack and deepening the sound. These two features give the impression of "warming". Yet there is no warmth, really, because it's hard to say that any part of the frequency range has been emphasized. The vocals and other instruments, operating in a similar range, are not brought forward or exposed. The mix is always even and the distance from the listener, the presentation of a given instrument depends primarily on the invention of sound and mastering engineers. Still, despite the fact that in comparison with an RCM Audio preamplifier the SPEC DOES sound warm and not very selective, all through the audition it was obvious that it has an inclination towards, a sort of "weak spot" for the records pressed from analog master tapes, not digital. Even if the latter were recorded in 24/96 or even 24/192 resolution. The difference between them was not clear at first, in that it was not about color, not even a resolution, at least not directly. Good productions of this type, i.e. from digital master tape, such as Making Music by Zakir Hussain from ECM, the new reissue of Spirit of Eden by Talk Talk, and The Doors box set, sound surprisingly convincing. They have a full sound and depth, with no trace of sharpening or brightening that may sometimes happen on an overly dry playback system.
    But it just takes listening to something analog from A to Z (actually, AAA), like the reissue of Groove Yard by The Montgomery Brothers and Somethin 'Else by Cannonball Adderley from Analogue Productions (45 rpm), or Study in Brown by Clifford Brown and Max Roach and Smokin 'At The Half Note Wes Montgomery, 200g vinyl Japanese pressings, to feel immediately what it is all about.
    We get a much deeper, smoother, slightly less muffled sound. The muffling I’m talking about doesn’t mean rolled-off, withdrawn treble. Such is SPEC’s nature and we get that with all records. It is something deeper. It is a feeling of "suppressing" the upper registers. I know this from auditioning speakers with poorly crossed over drivers or incorrect amount of damping material inside the cabinet. The vocal delivery of Mark Hollis, Talk Talk’s singer, warm, full, sensual, was shown in a slightly nasal way. Similarly sounded Alison Moyet's voice on the reissue of Upstairs At Eric's from Mobile Fidelity, and then the new, 180-gram vinyl version of Disintegration by The Cure. The same pattern repeated with each of these records: they sounded surprisingly nice, but the depth and the opening of the instruments were limited.
    However, this is not the only scheme governing that sound. It’s just that this one clearly shows the priorities of SPEC’s designers. Another indicator is the repertoire that is played.

    One of the axioms of the audio world, but the real audio world, not its part that only aspires to be "for real", is that the audio system should be universal. Audio equipment should sound equally well playing a large symphony orchestra and death metal Behemoth. There is truth in it. The same kind of truth as in the statement that audio equipment should not "interpret" the music and show exactly what was recorded on tape (disc, storage memory). In the real world, as such axioms relate more to the ideal world, the designer can choose between several equally attractive options. On one condition: it must lead to a better understanding of music, to its deeper experience.
    And so we connect music playback to the people – their preferences and beliefs. That applies both to the designing side – the engineer chooses the path he wants to follow, and to the listening side – the music lover must decide what he looks for in the listened-to music. Reviewing the REQ-1S EX, I had no trouble finding the answer: Yazaki-san is looking for the truth about music performance.
    To explain that, I must first say a few words about a debate on the superiority of one truth over the other, a debate as old as hi-fi itself. The question one needs to answer is of philosophical nature: should the designer attempt to bring the sound as close as possible to what we know from live performance, or should he rather be concerned with maximal accurate rendition of what has been recorded. Although it may seem otherwise, these are two completely different entities. In the first case, the recordings are somewhat uniformized as the character of audio equipment is "imposed" on them; in the second case we have a great differentiation of recordings, but also more problems carried over from the recording studio to our home. It would be best if the two could be reconciled, and actually in the absolutely top systems we have something of a "cease-fire" – both the one and the other remain in a delicate balance. In every other case, one of the sides needs to be chosen.
    The Japanese preamplifier joins the "live event" camp. It is best suited for albums relying on acoustic instruments, or electric ones recorded through miked-up guitar/organ amps. What we get then is a brilliant marriage of emotion and technique. The albums sound very smooth and coherent. The muffling of upper midrange, audible on recordings converted from digital sources, here is completely nonexistent. In absolute terms, the highs are rounded and the whole is rather warm. Yet we perceive it as advantages, not flaws. Although live instruments are more open and live soundstage is more expansive, the REQ-1S EX makes listening at home, guided by a different logic than live concert, richer, more "human" than "technical".


    Listening to music through the Japanese preamp is like having a bath in essential oils, resting on silk sheets, sipping caffè latte somewhere in sunny Italy, drinking a mug of Paulaner in a small beer bar in the center of Munich (I have practiced the latter for years ...). An excellent balance between individual components, a conscious choice regarding the sound, clear views on technical matters and, last but not least, a fantastic man behind all that makes listening to music with the REQ-S1 EX in the system like meeting an old friend – a bit of nostalgia, curiosity, but also a renewed sense of security.
    Sounds modeled by this preamplifier are never unpleasant. It’s an obvious departure from objective neutrality. Nevertheless, they never change the heart of the matter – the presentation of music, its value and naturalness. Thanks to that, all albums recorded and mixed in the analog domain, especially featuring acoustic instruments, come out great. Other sound a bit worse but never bad; their "worseness" is a technical problem of their producer and record label, not SPEC’s or ours. But maybe these discussion are purely academic anyway, arising from the needs of the review concentrated on showing differences. Listened to day after day, the preamp need for comparisons. Yes, it is possible to offer a better resolution sound. I’m just not sure if that’s really what everybody needs. I think most of us would simply like to sit down and forget about the world. If that’s true, let's do it with the REQ EX-S1.


    The Japanese preamp was compared against the RCM Audio Sensor Prelude IC preamplifier. It was fed signals from three different turntables: the Kuzma Stabi XL2 with the Benz Micro Switzerland RUBY Z cartridge, the Dr. Feickert Blackbird equipped with the Reed 3P tonearm and the Kansui and Zero cartridges from Miyajima Lab, as well as the Dr. Feickert Firebird with the Dynavector DV509 Mk2 arm and the Dynavector XV-1 cartridge.
    The preamplifiers were placed directly on the Acoustic Revive RAF-48F isolation platform, and the power supply unit on the RST-38. It was powered by the Acrolink Mexcel 7N-PC9300 power cord. The testing had a character of a comparison, with individual tracks and whole albums being auditioned. I devoted a separate session to auditioning the preamp with the Phasemation EPA-007 balanced headphone amplifier and the HiFiMAN HE-6 headphones, running in balanced mode.


    The full name of the reviewed preamplifier is the Designer Real-Sound Audio Phono Equalizer Amplifier REQ-S1 EX. The first part refers to a series of products, the second to a certain, developed technique and philosophy, the third to the type of equipment, and the fourth is the actual name.
    The unit is split into two enclosures – one houses the amplifying and equalizing circuit (PA-S1) and the other one the power supply (PU-S1). Both show a very meticulous build workmanship and are made of steel plates and a thick aluminum front. Underneath each enclosure is a screwed-on wooden plinth, forming a sort of anti-vibration platform, integrated with the device. Wood has been chosen intentionally; it has been prepared by Oak Village, a Japanese company specializing in wooden products, in keeping with the 1,300-year-old tradition of this country. The platform consists of four parts: a wooden plinth, made from smaller pieces glued together, and three shallow feet. Two feet are screwed on in the plinth’s cut-outs, the third one in the rear in a recess – they are simply differently mounted. It looks brilliant.


    On the unit’s front panel there are four nice, big toggle switches with small LEDs in their tips. The first switch selects the type of phono cartridge (or actually inputs) – MM or MC. The second one activates a subsonic filter, cutting off frequencies below 20 Hz (7950 µs). This is a modification of the RIAA curve from 1972, often referred to as EIC RIAA, introducing to the curve a fourth correction point. The associated LEDs are green. The third switch activates a cartridge degaussing system. When activated, it sends a small current through the cartridge coil to demagnetize it. It is essential to make sure that our cartridge can undergo this process. Finally, near the right edge there is a mute switch. The two latter switches have red LEDs.
    All connectors that we see on the rear panel come from Swiss Neutrik (although made in Liechtenstein). There are separate inputs for MM and MC cartridges, with two golden-plated cap grounding connectors between them. Both have the same ground potential and we can use either one. Apparently, the designers’ idea was to enable connecting two cartridges at the same time, or – even more likely – a MC cartridge and a step-up matching transformer. Next to the MM input we have an input capacity switch with two positions, 100 pF and 0 pF, and next to the MC input an input impedance switch to select between 20 Ω and 200 Ω. The output can be achieved in two ways – either from unbalanced RCA connectors or from balanced XLRs. The signal to them runs separately via quite long wires, which suggests a balanced topology of the amplifying circuit. As it turns out, this is not the case; the circuit is unbalanced and only the XLR output is balanced and driven by a separate IC. Near the left edge there is one more 7-pin XLR connector to power the unit from the external power supply. All XLR connectors are gold-plated and the RCA connectors are rhodium-plated.

    The electronic circuit is mounted on a large PCB and a smaller auxiliary board with relays and mute circuit. As mentioned by Mr. Yamazaki, the ultra-simple circuit is based on ICs. The designer believes that only these are capable of matching the advantages of tubes, which is a rather isolated view (although Mr. Friedrich Schäfer from ASR says something similar), but the results speak for themselves. The assumption is that the cartridge should “see” the lowest possible impedance. Hence, the MC input stage is based on op-amps using bipolar transistors, working well with low level, low impedance input signal. The MM input stage features FET input op-amps, optimal for high impedance cartridges. That is why we have separate sections for MM and MC cartridges.
    The input signal gets to the first gain stage based on one of the two op-amps. The MM input is handled by Burr Brown OPA627AM and the MC by Linear Technology LT1115. The latter, according to the manufacturer, is the lowest noise op-amp currently in production. Then, via beautiful oil coupling capacitors from Arizona Capacitors we get to the equalizing circuit. Up to this point the signal from the MM and the MC inputs is handled independently, with an active input selected by an Omron relay.
    Frequency compensation is based on a RC circuit. It features the most beautiful resistors I have ever seen in audio equipment, just like the accompanying capacitors, again from Arizona Cap. The latter are manufactured to SPEC specification and bear its logo. They are bypassed with Bennic mica capacitors. The most important seems to be their small tolerance. The final gain stage is built on two more op-amps: International Semiconductors LME49860 and Burr Brown DRV134. The latter is a balanced line driver and it drives the XLR output. The coupling wires to the output connectors are quite long. Let me add at this place that all internal wiring uses Belden cables. There are plenty of them and they are run in bundles. Attention to star grounding is evident throughout. And one more thing: each possible component is wrapped in vibration damping material. Also, the whole inside surface of the top panel is covered with a kind of vibration-dampening mat, doubling as RF noise shielding.


    The power supply looks just as good as the amplifying unit, featuring the same casing and a nice front panel with the anti-vibration platform to boot. The front sports only one switch but it is one to behold: a toggle switch with locking mechanism. It looks superb! The rear panel features an IEC mains socket, a fuse and a power-out connector – another multi-pin XLR from Neutrik. As visible from the inside, the IEC socket has an integrated simple noise filter.
    As it might have been expected and as I know from a SPEC amplifier, the power supply is extremely complex. It is mounted on a large circuit board in the form of two separate sections for the left and the right channels. They are powered by a large R-core transformer from Kitamura Kaiden. Next to it is a smaller transformer, powering relays and LEDs in the main unit. The power supply powering the main amplification circuit could easily drive a medium-sized amplifier: it features discrete SIC type Schottky rectifying diodes and two large filter capacitors per channel. They are followed by Elna Silmic II capacitors and voltage controllers ICs. There are more Elna capacitors in the output, bypassed by large oil capacitors from Arizona Capacitors and Mallory. The latter brand is currently owned by Cornell Dubilier, another American specialist whose capacitors are used in components from e.g. Manley. All used oil capacitors are high voltage types (400 and 600 V). Excellent job!


    - Turntable: AVID HIFI Acutus SP [Custom Version]
    - Cartridges: Miyajima Laboratory KANSUI, review HERE | Miyajima Laboratory SHILABE, review HERE | Miyajima Laboratory ZERO (mono) | Denon DL-103SA, review HERE
    - Phono stage: RCM Audio Sensor Prelude IC, review HERE
    - Compact Disc Player: Ancient Audio AIR V-edition, review HERE
    - Multiformat Player: Cambridge Audio Azur 752BD
    - Line Preamplifier: Polaris III [Custom Version] + AC Regenerator, regular version review (in Polish) HERE
    - Power amplifier: Soulution 710
    - Integrated Amplifier: Leben CS300XS Custom Version, review HERE
    - Stand mount Loudspeakers: Harbeth M40.1 Domestic, review HERE
    - Stands for Harbeths: Acoustic Revive Custom Series Loudspeaker Stands
    - Real-Sound Processor: SPEC RSP-101/GL
    - Integrated Amplifier/Headphone amplifier: Leben CS300XS Custom Version, review HERE
    - Headphones: HIFIMAN HE-6, review HERE | HIFIMAN HE-500, review HERE | HIFIMAN HE-300, review HERE | Sennheiser HD800 | AKG K701, review (in Polish) HERE | Ultrasone PROLine 2500, Beyerdynamic DT-990 Pro, version 600 - reviews (in Polish): HERE, HERE, HERE
    - Headphone Stands: Klutz Design CanCans (x 3), review (in Polish) HERE
    - Headphone Cables: Entreq Konstantin 2010/Sennheiser HD800/HIFIMAN HE-500, review HERE
    System I
    - Interconnects: Acrolink Mexcel 7N-DA6300, review HERE | preamplifier-power amplifier: Acrolink 8N-A2080III Evo, review HERE
    - Loudspeaker Cables: Tara Labs Omega Onyx, review (in Polish) HERE
    System II
    - Interconnects: Acoustic Revive RCA-1.0PA | XLR-1.0PA II
    - Loudspeaker Cables: Acoustic Revive SPC-PA
    System I
    - Power Cables: Acrolink Mexcel 7N-PC9300, all system, review HERE
    - Power Distributor: Acoustic Revive RTP-4eu Ultimate, review HERE
    - Power Line: fuse – power cable Oyaide Tunami Nigo (6m) – wall sockets 3 x Furutech FT-SWS (R)
    System II
    - Power Cables: Harmonix X-DC350M2R Improved-Version, review (in Polish) HERE | Oyaide GPX-R (x 4 ), review HERE
    - Power Distributor: Oyaide MTS-4e, review HERE
    - Portable Player: HIFIMAN HM-801
    - USB Cables: Acoustic Revive USB-1.0SP (1 m) | Acoustic Revive USB-5.0PL (5 m), review HERE
    - LAN Cables: Acoustic Revive LAN-1.0 PA (kable ) | RLI-1 (filtry), review HERE
    - Router: Liksys WAG320N
    - NAS: Synology DS410j/8 TB
    - Stolik: SolidBase IV Custom, read HERE/all system
    - Anti-vibration Platforms: Acoustic Revive RAF-48H, review HERE/digital sources | Pro Audio Bono [Custom Version]/headphone amplifier/integrated amplifier, review HERE | Acoustic Revive RST-38H/loudspeakers under review/stands for loudspeakers under review
    - Anti-vibration Feets: Franc Audio Accessories Ceramic Disc/ CD Player/Ayon Polaris II Power Supply /products under review, review HERE | Finite Elemente CeraPuc/ products under review, review HERE | Audio Replas OPT-30HG-SC/PL HR Quartz, review HERE
    - Anti-vibration accsories: Audio Replas CNS-7000SZ/power cable, review HERE
    - Quartz Isolators: Acoustic Revive RIQ-5010/CP-4
    - FM Radio: Tivoli Audio Model One