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Integrated amplifier/power amplifier


Price (at the time of the test):
60 000 EUR (pair)

Contact: 6th Fl. Shin Kioi-Chobuilding
4-1 Kioi-Cho Chiyoda-Ku
Tokyo 102-0094 ǀ JAPAN


Provided for test by MUSON PROJECT

SPEC Corporation is a Japanese company founded by Mr. SHUZOU ISHIMI, in order to achieve one goal: to provide a tube sound with solid-state amplifiers. The RPA-MG1000 amplifier is its latest and the most expensive product. And it's a Class D one.

f we were to adopt an evolutionary theory of changes in audio, we would have to assume that we are moving from less advanced to more advanced designs, in fact – that these are getting better and better. However, as we all know, evolution in our world is not linear, often designers return to older solutions, sometimes redeveloping them, to achieve new, better results.

It is worth notice, however – that's my opinion at least - that in many respects a real progress has been made in recent years, in a faster and faster pace. Not in every respect, but still. I believe it is not only my opinion - I just finished reading Isaac Markowitz's Why Do Any of This At All in the Stereophile magazine, in which he concludes his observations about the evolution of his own audio system in this way:

When it comes to sound reproduction, it seems that we are light years ahead, compared to where we were 20 years ago. One almost feels that the best products simply pick and reject from music all that is not music – like an electric equivalent of Rodin who sees a marble block as a ready sculpture and all the rest just isn't art.

Isaac Markowitz, Why Do Any of This At All, „Stereophile” 2019, vol. 42 No. 2, p. 138

But its is just mine, sorry, our opinion, that you may agree with or not.

| SPEC and Class D

In this approach, I seem to be an ally of the SPEC - a Japanese specialist, known primarily for its amplifiers. We have already written about the company many times, also about the main engineer of SPEC - now retired - Mr. Shirokazu Yazaki (more in My private history of audio and in the Real-Sound Processor RSP-AZ9EX review).

This time, however, I am facing a special challenge - this is the company known so far for excellent, expensive amplifiers, has prepared an amplifier costing even more, the RPA-MG1000 – which is one of the most expensive amplifiers on the market. This 60,000 EUR device is nominally a power amplifier, but in fact is an integrated amplifier. We'll come back to that later.

The most important fact, apart from the price, is that the SPEC amplifiers operate in class D. In the company materials that I received in May 2013 during the High End Show, when I first met Mr. Shirokazu Yazaki and Mr. Banno Tsutomu - currently the company's chief engineer – I found a meaningful drawing presenting progress: from tube amplifiers, referred to as "the 1st generation", through classic solid-state amplifiers, or "the 2nd generation", up to new amplifiers in the class D, being the 3rd generation of amplifiers in general.

And it is not at all that Yazaki-san and Banno-san do not like tubes, in fact they are tube connoisseurs, they design wonderful amplifiers of this type. It is simply that they see the advantages of new technology. In order for them to be utilized and for this to make sense, one should approach the design in the right way and choose the right solutions. For them, the key to achieving top sound from semiconductors is the Class D operation.

If we put our prejudices for a moment aside - because there are plenty of poor sounding class D amplifiers - and focus on the basics, maybe it will be easier to understand what I'm going to write about in the “Sound” section.

| RPA-MG1000

I think that SPEC's crew have been fascinated by the simplicity of this type of circuits. But simplicity is something that can easily turn into crudeness. That is why so much attention has been devoted even to the tiniest details in the amplifiers of this company, including the latest monoblocks.


We/SPEC corp. established in Jan 2010 have developed various products with particular feeling for "REAL SOUND". 2019 is the year of SPEC brand recognition milestone in the 10th year, that is why we launched this model as a new flagship. We put an end to discussion about the class of amplifiers and finally we were able to launch the RPA-MG1000 which took for a year and a half for the development to offer "REAL SOUND" for a lot of music fans of all over the world.

People responsible for this design: Banno TSUTOMU-san (on the right) and Yasuhiro YAMAKAWA-san (on the left).

We use plenty of naturally derived resources which is not used any other amplifier manufacturers, and everyone can listen natural musicality without tired of listening. The features of D class amplifiers are high efficiency and low heat generation, high dynamic characteristics, strength against backward electromotive current.

To take advantage of these features, a wood base vibrating earth structure is adopted the AUSTRIAN SPRUCE and ITAYA MAPLE from Hokkaido of Japan and walnut wood. We also developed and adopted original capacitor “HIBIKI-ICHI” (joint development with Nichikon). Moreover, for sound quality parts, the RPA-MG-1000 has SOSS circuit technology (Spec Original Sound Snubber; more about „snubber” circuits HERE). The very large capacitor is produced from stacked Ruby Mica of State of Bihar in north India. This capacitor produces high quality and high transparency, purity. On the other hand, you can enjoy listening with SPEC original hermetic seal oil condenser if you like it better.

RPA-MG1000 flow chart.

We would like to listen to the music long time without listening exhausted, can be listen in a well-balanced even with a small volume and also wanted to deliver a realistic sound that makes you want to hear with a bigger sound. These reason why we launched this RPA-MG1000.

Attenuator | The RPA-MG1000 features two line inputs, XLR and RCA. It can operate like a classic power amplifier with an external preamplifier. One chooses this option with a small knob on the back panel and then it is possible to adjust input sensitivity. But these monoblocks were intended to operate as an integrated amplifier. In the company materials I mentioned, a lot of space was devoted to showing that it is better to send a high-amplitude signal to an amplifier and attenuate it just before the output than to send a low amplitude one.

Modulator | The heart of every class D amplifier is a circuit that converts an analog signal into a series of pulses that control the output transistors - these can either be fully "open" ("ON") or completely "closed" ("OFF"). Company materials leave no doubt about it: "The performance of a D-class amplifier depends on how manufacturer implements extremely precise PWM switching" (underlining - SPEC). Specially for this role, SPEC developed the IRS2052SM circuit together with the American company International Rectifier.

This circuit controls a pair - per channel - of tiny, extremely linear, MOS-FET transistors, which allowed to achieve an output of 300 W at 8 Ω and 600 W at 4 Ω. In their output there is a classic filter composed of hand-wound coils, carefully selected in terms of the sound they offer, as well as capacitors. However, SPEC has its own opinion on capacitors. This is an Class D amplifier, but fully analog.

Capacitors | Starting from the very first amplifier and the first filter, Mr. Shirokazu Yazaki bet on two types of capacitors - Arizona Capacitors oil capacitors, modeled on the model known from the 1960s, as well as newer mica capacitors. The latter belong to the MC-DA series and vary in their capacity. Their appearance, however, is similar - they are large, black cuboids. They are made of laminates, which is to reduce the inductance, and the material comes from India, it is the best mica of this type, called "ruby mica". The electrodes are made of sputtered silver.

The tested amplifier utilizes both types of capacitors. This is because SPEC gives the user an option to choose the sonic character. For the first time this option was introduced in the REQ-S1EX phono preamplifier from 2013, and with this model this choice was brought to extremes. On a separate PCB, after the output filter, there are two sets of capacitors and resistors. One of them is named "musicality" and the other "neutrality". It is not a tone equalizer, because it does not change the frequency response (bandwidth measurements are identical for both options), but a system that changes character of the sound. One chooses between the two modes using a small switch on the back panel.

Power supply | One of the features of almost all Class D amplifiers is a switched mode power supply. It allows manufacturers to reduce the weight and price of the device, and from the technical standpoint it allows to adjust its operation using the amplifier's circuit. Specialist Japanese companies, such as Soul Note and SPEC, decided to take a different approach – they use linear power supplies.

SPEC utilizes large R-core transformers - the RPA-MG1000 features a powerful transformer with an output of 800 W per channel. Two separate power supplies work with each of them - one for low-current circuits, this one is regulated, and the other one for output circuits. Both feature oil capacitors, the latter additionally two large electrolytic capacitors. It uses also high power rectifying bridges composed of high-speed Schottky diodes, which minimizes the noise generated during switching.

As I said, the tested amplifier has been divided into four units - two of them are amplifiers for the left and right channel, and other two are power supplies, again for each channel separately. Both parts are connected with quite short cables - separate ones for the high-current section and for the low-current, stabilized one.

Chassis | SPEC amplifiers look stunning. Their build is extremely sturdy. Their majestic appearance is a result of not only a tasteful design, but also technical goals. It is a fact, that Class D amplifiers generate a lot of high frequency noise and are extremely sensitive to vibrations.

SPEC amplifiers, including these under review, feature particularly robust chassis. In this case, it is built of thick, multilayer steel and aluminum sheets. In turn, the bottom and sides are made of wood, the same one that is used for the body of a violin. Each of the four units features three feet, made of various kinds of wood. The whole has been "tuned" - literally - in listening sessions. So it's no wonder that it's very important for sound quality what the amplifiers are placed on. The best option is wood, but used in the high quality racks.

The SPEC amplifier has been designed to work directly with the signal source as an integrated amplifier - and so it has been tested. It was placed on two shelves of Finite Elemente Master Reference Pagode Edition rack – the power supplies on the lower level, and the amplifiers on the top level. Since there was no space left for the Ayon Audio CD-35 HF Edition Player, I placed it on a temporary stand, consisting of a stand for the Sonus faber loudspeakers and the Acoustic Revive RAF-48H anti-vibration platform.

The amplifiers were powered using the Acoustic Revive Absolute-Power Cords, and were connected with speakers using Siltech Triple Crown cables; During a separate listening session I used Western Electric NOS speaker cables, which Mr. Yamazaki-san once sent me. The Player delivered signal to amplifiers using a balanced Siltech Triple Crown interconnect. However, I very good results were achieved also with the amazing Acrolink Mexcel 8N-A2080III Evo.

The SPEC amplifiers were compared to my reference system, i.e. Ayon Audio Spheris III preamplifier and Soulution 710 power amp. I also used my notes and memories from other tests of top amplifiers, such as: Kondo OnGaku, Phasemation MA-1000, AudioPax Maggiore l50 + m50 and Thöress Dual Function Preamplifier + 845 Mono.

SPEC in "High Fidelity”
  • AWARD: BEST PRODUCT 2017 | SPEC RSA-F33EX | integrated amplifier
  • REVIEW: SPEC RSA-F33EX | integrated amplifier
  • REVIEW: SPEC RSP-901EX Real-Sound Processor
  • EDITORIAL | Column: My private history of audio | SHIROKAZU YAZAKI
  • REVIEW: SPEC Designer Audio REQ-S1 EX | phonostage
  • REVIEW: SPEC RSA-V1 | integrated amplifier
  • REVIEW: SPEC RSP-101 | Real-Sound Processor

  • Recordings used for the test (a selec- tion)

    • Andrzej Kurylewicz Quintet, Go Right, Polskie Nagrania „Muza”/Warner Music Poland 4648809, „Polish Jazz | vol. 0”, Master CD-R (1963/2016);
    • Aquavoice, Silence, Zoharum ZOHAR 168-2, Master CD-R (2018);
    • Ariel Ramirez, Misa Criolla, José Carreras, Philips/Lasting Impression Music LIM K2HD 040, K2HD Mastering, „24 Gold Direct-from-Master Edition UDM”, CD-R (1964/2009).
    • Enya, 6 Tracks, WEA Records/Warner-Pioneer Corporation 20P2-2725, CD (1989)
    • J.S. Bach, Sonatas & Partitas vol. 1 BWV 1004-1006, wyk. Isabelle Faust, Harmonia Mundi HMC 902059, CD (2010)
    • Mario Suzuki, Masterpiece II: Touching Folklore Music, Master Music XRCD24-NT021, XRCD24 (2018)
    • Mayo Nakano Piano Trio, MIWAKU, Briphonic BRPN-7007GL, Extreme Hard Glass Master CD-R (2017);
    • Nat ‘King’ Cole, The Nat King Cole Love Songs, Master Tape Audio Lab AAD-245A, „Almost Analogue Digital”, Master CD-R (2015);
    • Rage Against The Machine, Rage Against The Machine, Epic/Audio Fidelity AFZ 244, „Limited Edition | No. 0115”, SACD/CD (1999/2016)
    • Renaissance, Scherezade, Warner Bros. Records/Audio Fidelity AFZ 183, „Limited Edition | No. 0281”, SACD/CD (1975/2014)
    • The Oscar Peterson Trio, We Get Request, Verve/Lasting Impression Music LIM K2HD 032, K2HD Mastering, „24 Gold Direct-from-Master Edition UDM”, Master CD-R (1964/2009)

    I have to admit to one thing that I "do" probably in all of my tests: I approach each device differently, I treat them differently. It may seem odd, because the basic task of the observer, the researcher - and this is (or should be) what reviewers and critics are - is an unbiased assessment, but in my case reality is different.

    The different treatment I've mentioned is in my case a different response to what I hear. In all other respects, all subsequent devices are the same for me – just "black boxes" that I must describe, interpret the description and finally evaluate them. Until the first track is played, all products, starting from - say - an amplifier for 1000 zlotys, ending with the top high-end product such as the reviewed SPEC monoblocks, they are all the same for me.

    However, when I hear the first beats, the first tracks, when a pile of music discs grows around me, I begin to interact with the device and from this moment on I treat it differently. I start to “talk” to it, just like I talk to people I meet. With some, I exchange kind greetings, with some others we joke casually, and with yet another group we only exchange information needed to do some work (action).

    A dialog | The tested SPEC RPA-MG1000 amplifier, just like the Kondo OnGaku, like the Ayon Audio CD-35 HF Edition, like the Siltech Triple Crown cables and some other audio products that I particularly value, is something (someone) completely different. There are some people who seem so interesting that we want to talk to them, dispute some issues, and often just listen to them. These are people whom we trust, whom we respect. Every now and then, such feedback between us and an audio device happens suddenly, during the meeting, I mean one that was not initially "set" by our expectations.

    That's what happened with me and the SPEC amplifier - although I knew it would be good, after all I know, respect and admire both the founder of the company, Mr. Yamazaki-san, as well as its chief engineer, Mr. Banno-san, and the whole team, though since I was also aware, that it were very expensive devices, I had concerns whether such pricing wasn't exaggerated, or whether it was style over substance.

    I will not even try to answer if these amplifiers should cost so much money, because I do not know. Luxury products, including art, are difficult to put a price to and what really counts is how well do they meet our needs and dreams. I will discuss the performance and its influence on me.

    Naturalness | With the reviewed amplifier I entered the dialog almost immediately, and after a while I mainly listened to it, only every now and then "asking" it some short questions. Because this is a remarkable device. It offers an incredibly refined. performance. And refinement means you can not hear everything right away and that you need to have the right preparation - through listening sessions and concerts - to appreciate it.

    It is an absolutely natural sound. Natural in such a beautiful way that I only once heard something similar in my room - with the mentioned OnGaku, an icon of tube amplifiers. There is such softness in this sound, such a space, that the listening position disappears, speakers disappear, system disappears - we do not have a feeling that we are dealing with mechanically reproduced music, and simply with music.

    And that's because the amplifier seems to be dancing to the music, if I may say so. Almost all the other amplifiers I know, except - literally - a few exceptions, sound clumsy in comparison. Even if they seem more "accurate", more "real". And it doesn't matter what music we listen to.

    Treble | All Master CD-R discs that I have and all I just had to listen to, even if only in short fragments, sounded amazing. Those of you with whom I had the pleasure to compare CDs and Master CD-Rs during the Audio Video Show know, that the latter sound in a more open, much more precise and resolving way, which in lesser quality systems leads to brightness, and with the best ones, creates an impression of warmth - but without smearing, without losing some of the details.

    The SPEC amplifier conveys this in a remarkable way. Metal cymbals, say, from Polish Jazz discs, sound wonderfully sonorous, while maintaining their weight and density. It was as if I listened to them from hi-res files in the JACEK GAWŁOWSKI mastering studio, as I remembered it. And there is this wonderful vividness, usually associated with vinyl. too. On the one hand, it goes even further in this direction, it's a kind of "simultaneous presence" of analogue master tapes, but with a twist, that is, with the softness that we get only with their vinyl copy.

    Bass | The amplifier sounds rather lightly and spatially – as I already said. It is the “lightness” of power that knows its capabilities and limitations. Because the bass here is perfectly saturated, beautifully controlled and powerful. I focused on it particularly when listening to the Master CD-R with Aquavoice recordings. I do not know if you remember, but TADEK ŁUCZEJKO, who's the man behind this name, said during the listening session of his material on my system that he did not even realize that there were so many sounds in those recording, that the bass was so well extended.

    And it goes unbelievably low and is just strong. SPEC handled it perfectly well, after all it is a high power amplifier with a powerful power supply. It was a similar class as with my Soulution 710 amplifier and I am saying it with the seriousness that this fact deserves - it's probably the first such case. The Swiss amplifier goes even a bit deeper down, you can't really complain about it. Also the control it provides is slightly better, but again, the difference is so small, that you can't even use it as Soulutions advantage. Generally, it's the same class. No tube amplifier is able to deliver such performance with large speakers.

    Vocals | However, the vocals were reproduced better than in my system consisting of the aforementioned power amplifier and the Ayon Audio Spheris III linear preamplifier. Even better, but not by much, they sounded with Kondo OnGaku. All three delivered similar fantastic quality midrange, but - let's be honest - my system would be in third place in this competition. It's all about the way the images are constructed - SPEC builds large phantom images, that are dense and deep. It does not cut them out of the rest of the presentation, it is a remarkable "sticky" sound so to speak, and it draws our attention to them through particular constructions of the soundstage, where the foreground is the most important of it.

    It was the case, for example, with an excellent copy of the Master CD-R straight from the analog tape of Nat "King" Cole, but "regular" CDs sounded similarly, like Enya's compilation prepared in Japan by Pioneer under the enigmatic title 6 Tracks. It was a real treat! The vocal was stable, in the middle, most important, but without zooming in on it. The whole soundstage was pushed back, far behind the speakers. Besides, not only behind loudspeakers - when I closed my eyes, the sound was even wider, and also came from their sides. But always what was in front of me played a key role.

    Spacing | Only the best, absolutely best amplifiers, usually tube ones, present sounds in space in such a natural way. Even more accurately, though not so softly, the Ancient Audio Silver Mono amplifiers are able to do it, in an equally soft, but with a bit less momentum it is presented by the Kondo OnGaku, and my system does it in a bit darker and somewhat less spectacular way. To study this respect of the presentation closer, I listened to the Bach's Sonatas & Partitas vol. 1 performed by Isabelle Faust.

    I reached for it first of all, because I like this CD very much, and secondly - I wanted to prepare for a concert that I'm going to soon. As part of the ICE Classic series, three concerts will take place this year at the ICE Krakow Congress Center. One of them - Sir Simon Rattle and the London Symphony Orchestra - is already behind us, and two - Isabelle Faust with Philippe Herreweghe and Orchester des Champs -Elysées (March 17th) and countertenor Philippe Jaroussky together with Ansemble Artaserse (3 July) – are still before us.

    Anyway, Bach's sonatas and partitas were released by Harmonia Mundi on a Red Book CD – that's the one I have. For years, however, I've been dreaming about the Japanese King Records release. It was released on a single-layer SACD, with both parts of this set. Unfortunately, it is very expensive - if it even appears on eBay, its price is never lower than $ 135 (plus shipment and taxes), and usually stays close to $ 200.

    For a moment, however, I was able to forget about it. With SPEC amplifiers and the Ayon Audio CD-35 HF Edition player this CD sounded phenomenal. A huge space I was close to, translucent to the sound of Stradivarius violin (the Sleeping Beauty violin from around 1704), which was at the same time far away, in perspective, but also at my fingertips. And that's how this amplifier sounds like with every musical material. And even some heavy tracks, generally requiring lots of power and slam, sounded with SPEC really well, better then with any tube amplifier.

    Dynamics | Finally, let me shortly talk about dynamics. The huge output of the amplifier would suggest an “avalanche of sound”. However, I have already discussed the bass, so we know that it is not a typical "power amp". The headroom it has is used to convey power, but the power of space, power to be convey quick changes, but within a larger whole. An attack of individual sounds seems slightly rounded, slightly polished and don't ever expect a hard, unambiguous attack.

    Therefore, it is not an amplifier without flaws, there is no such thing. I does not offer particular selectivity, because its sound reminds that of an analog tape, that does not offer clear layers of the stage, or particularly distinct imaging. These elements appear only on its copies – vinyl, SACD and CD (although SACD is most similar to the tape) releases. Anyway, if you are looking for an amplifier that will clearly outline each instrument - forget about SPEC. The device fantastically differentiates everything except that it does it in a smooth, fluid way. It is not a black and white, flat photo with high contrast, but rather a 3D pastel.


    The RPA-MG1000 amplifier is one of the few best amplifiers I've heard, regardless of price, design and brand. It is extremely characteristic. This is the sound of tube amplifiers - Kondo OnGaku, Phasemation MA-1000 and others. It sounds warm, dense, creates a huge space, but placed behind speakers. It delivers a powerful, large, refined foreground, but it does not push it in front of the speakers. The sound is intimate, but open and airy. Plus there is this beautiful bass! GOLD Fingerprint!

    Specifications (according to manufacturer)

    Nominal output: 300W/4Ω | 150W/8Ω
    Frequency range: 10 – 30 000Hz (+/- 1dB)
    THD: 0.02% (1kHz, 80% output)
    Power amp dimensions (W x H x D): 450 x 170 x 430 mm
    Power supply dimensions (W x H x D): 450 x 170 x 455 mm
    Power amp weight: 27 kg
    Power supply weight: 20 kg


    Reference system 2018

    1) Loudspeakers: HARBETH M40.1 |REVIEW|
    2) Line preamplifier: AYON AUDIO Spheris III Linestage |REVIEW|
    3) Super Audio CD Player: AYON AUDIO CD-35 HF Edition No. 01/50 |REVIEW|
    4) Stands (loudspeakers): ACOUSTIC REVIVE (custom) |ABOUT|
    5) Power amplifier: SOULUTION 710
    6) Loudspeaker filter: SPEC REAL-SOUND PROCESSOR RSP-AZ9EX (prototype) |REVIEW|
    7) Hi-Fi rack: FINITE ELEMENTE Pagode Edition |ABOUT|


    Analog interconnect SACD Player - Line preamplifier: SILTECH Triple Crown (1 m) |ABOUT|
    Analog interconnect Line preamplifier - Power amplifier: ACOUSTIC REVIVE RCA-1.0 Absolute-FM (1 m) |REVIEW|
    Speaker cable: SILTECH Triple Crown (2.5 m) |ABOUT|

    AC Power

    Power cable | Mains Power Distribution Block - SACD Player: SILTECH Triple Crown
    Power (2 m) |ARTICLE|
    Power cable | Mains Power Distribution Block - Line preamplifier - ACOUSTIC REVIVE
    Power Reference Triple-C (2 m) |REVIEW|
    Power cable | Mains Power Distribution Block - Power amplifier - ACROLINK Mexcel 7N-PC9500 |ARTICLE|
    Power cable | Power Receptacle - Mains Power Distribution Block: ACROLINK Mexcel 7N-PC9500 (2 m) |ARTICLE|
    Power Receptacle: Acoustic Revive RTP-4eu ULTIMATE |REVIEW|
    Anti-vibration platform under Acoustic Revive RTP-4eu ULTIMATE: Asura QUALITY RECOVERY SYSTEM Level 1 |REVIEW|
    Power Supply Conditioner: Acoustic Revive RPC-1 |REVIEW|
    Power Supply Conditioner: Acoustic Revive RAS-14 Triple-C |REVIEW|
    Passive filter EMI/RFI: VERICTUM Block |REVIEW|


    Speaker stands: ACOUSTIC REVIVE (custom)
    Hi-Fi rack: FINITE ELEMENTE Pagode Edition |ABOUT|
    Anti-vibration platforms: ACOUSTIC REVIVE RAF-48H |ARTICLE|

    • HARMONIX TU-666M "BeauTone" MILLION MAESTRO 20th Anniversary Edition |REVIEW|


    Phono preamplifier: Phono cartridges: Tonearm (12"): Reed 3P |REVIEW|

    Clamp: PATHE WINGS Titanium PW-Ti 770 | Limited Edition

    Record mats:


    Headphone amplifier: AYON AUDIO HA-3 |REVIEW|

    Headphones: Headphone Cables: Forza AudioWorks NOIR HYBRID HPC