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This review first appeared in the May 2013 issue of hi-end hifi magazine High Fidelity of Poland. You can also read it in its original Polish version here. We publish its English translation in a mutual syndication arrangement with publisher Wojciech Pacula. As is customary for our own articles, the writer's signature at review's end shows an e-mail address should you have questions or wish to send feedback. All images contained in this review are the property of High Fidelity or SPEC Corp. - Ed

Reviewer: Wojciech Pacula
CD player: Ancient Audio Lektor Air V-edition
Phono preamplifier: RCM Audio Sensor Prelude IC
Cartridges: Miyajima Laboratory Shilabe & Kansui
Preamplifier: Ayon Audio Polaris III Signature with Regenerator power supply
Power amplifier: Soulution 710
Integrated amplifier/headphone amplifier: Leben CS300 XS Custom
Loudspeakers: Harbeth M40.1 Domestic + Acoustic Revive custom speaker stand
Headphones: Sennheiser HD800, AKG K701, Beyerdynamic DT-990 Pro 600Ω vintage, HifiMan HE6
Interconnects: CD/preamp Acrolink Mexcel 7N-DA6300, preamp/power amp Acrolink 8N-A2080III Evo
Speaker cable: Tara Labs Omega Onyx
Power cables (all equipment): Acrolink Mexcel 7N-PC9300
Power strip: Acoustic Revive RTP-4eu Ultimate
Stand: Base IV custom under all components
Resonance control: Finite Elemente Ceraball under CD player, Audio Revive RAF-48 platform under CD player and preamplifier, Pro Audio Bono PAB SE platform under Leben CS300 XS
Review component retail in Poland: €14.000


This story began over a year ago when I prepared materials for our seventh annual Japanese issue of HighFidelity. I asked Mr. Yoshi Hontani for help whom I wrote of in the past. Together with his son Elia he made a few appointments for me with manufacturers from his home country which were completely unknown to me and thus full of secrets. This is how I first came across Audio Replas, fo.Q, SAEC, Air Cable (Okutsu Denko Co.) and the signature product from SPEC Corp., their RSA-V1 amplifier reviewed here. A few months after that review I received a very nice letter from Mr. Shirokazu Yazaki, chief SPEC designer, thanking me for my accurate observations and sharing his experiences. He also sent me a brief report of a New Year's Eve meeting during which he and others had auditioned his latest design, a tube amplifier based on very exotic Western Electric tubes he crafted for a friend. Thus began our e-mail friendship. It's unusual to find a person separated from us by thousands of miles, by a completely different culture and by a very different professional background yet with whom we clearly share similar sensibilities, tastes and views. After a while the idea of a phono reference preamplifier began to crystallize. But first some background on the company and its boss. This is how Yoshi Hontani first introduced Mr.Yazaki to me:

"Mr.Yazaki of SPEC is a very interesting engineer. He loves the sound of 300B single-ended amplifiers and has been continuously upgrading his own 300B SET across 38 long years whilst aiming for the ultimate sound. To solve the only disadvantage of his 300B SE amp—insufficient power to drive today's low-efficiency speakers—he finally decided to replace his 300B output tubes with the newest highest-grade PWM switching devices supported by a linear power supply and West Cap-type vintage oil caps. This means that whilst the output tubes were replaced by switching transistors, the basic theory remains that of a valve amp. Although the ultimate target sound should be the same, the sound of these amplifiers is different at this stage. It means that neither tube nor solid-state amps are perfect but there currently seems no solution for further improvements. Some Japanese audio journalists commented already that these latest SPEC amplifiers could be the future of audio amplifier design." - Yoshi Hontani

Here is how Mr.Yazaki sketched out his own background: "My own committed audio hobby started in 1971 when I had just graduated from university and joined TEAC as a mechanical engineer. At the time they were one of the most famous tape recorder makers in the world. I'd been interested in audio products already, especially the dynamic motion of open-reel tape transports. But I suppose at the bottom of it I was basically just another music lover fond of instrumental and vocal Jazz.


"As a tube amplifier fan I became terribly excited when fine European tubes first started to arrive in Japan by the early 1970 thanks to Jean Hiraga. He started a business importing mainly vintage British tubes to Kobe in Japan. I was so stimulated by DIY articles on how to make your own tube amplifiers with vintage European glass from specialized monthly magazines like MJ or Radio Engineering. I'd never before actually heard the sound of such a tube amplifiers. I'd only read about them to imagine both beautiful sonics and exotic cosmetics. But finally I could experience them and became deeply impressed by the superb and very real sound of single-ended direct-heated triode power amplifiers coupled to high-efficiency Altec A-5 hornspeakers at the Tokyo Audio Fair of 1971. This experience became the impetus which would actually spur on and shape my own audio career.


"I decided to start with a single power-triode amp and then collect a horn speaker system. First I started to build up the very simple GEC DA30 non-feedback SET (PX25A or CV1178 British power triode; these days a DA30 is so rare that I suppose it’s only found in a museum even in England) following a June 1972 article by Mr. Anzai in MJ magazine. This circuit I completed in early 1973. The amp was composed of a Western Electric 310A driver tube, a Telefunken GZ34 or Western Electric 274B rectifier and a GEC DA30 power triode. The reason I selected the DA30 over the famous Western Electric 300B was that its HF response was superior in this non-feedback circuit.


"So my SE amplifier was composed of a US-made driver tube and a British power triode. It might have been a rare case but I never regretted my selection because of Mr. Anzai's excellent circuit design. Now already 40 years have passed but each time I hear the sound of a DA30 driven by a WE310A, I enjoy the natural rich midrange and glorious tonal qualities of vintage UK valves and the powerful lower upper bass/lower midrange of the special US tube. Curiously enough 40 years after experimenting with this very primitive valve amplifier I was led to a new generation of high-tech class D components.


"About the hornspeaker system, at the end of 1973 I first got a pair of used vintage Altec 414A woofers in good condition. It’s a 12-inch woofer but compared to the noted 15-inch 416A has more speed across its range. I thought it might prove better for home use. Now I had to decide between Altec, JBL and Onken drivers for the horn. I finally decided on the latter for its exceptionally flat response and the organic natural tonal character of the wooden horn with its amazing Japanese craftsmanship. I ordered the mid-high Onken OS-NEW500MT driver and matching SC-500WOOD wood horn in December of 1973 but didn't receive them until early 1975. It took much time to make these drivers due to the craftsmanship Mr. Koizumi insists on to deliver perfection to his customers. In 1997 I added the OS-5000T Esprit tweeter and the structure of my high efficiency hornspeaker system was complete.


"I should also say something about my Marantz 7 preamp. In 1979 Marantz Japan released the kit form of the Marantz 7 as the Marantz 7K. I had adored the Marantz 7 because of its legendary musicality and beautifully balanced design. So I built up the kit but with better parts. I learned so much about how we can get fine musical tone from building that kit. Of course I made continuous improvements to my Marantz 7 up to the present. That means this Marantz 7 really was a good professor for me on audio technology.
"I don’t have sufficient time to describe my professional career over the last 40 years in detail. I would simply like to mention a few memorable products which I either developed on my own or as manager or general manager of an engineering department. I worked with TEAC as mechanical engineer for about 4 years designing open-reel tape recorders. Here I think I learned everything important about tape-transport technology. I drew countless plans for mechanical parts for their TEAC A-7300, a high-performance 2-track 38cm/sec semiprofessional tape recorder. After these 4 years I moved on to Pioneer where for the next 17 years I was team leader or manager of the engineering department for mainly their cassette recorders. At this time I was already an expert in designing high-performance dual-capstan mechanisms. My interest and task was how to reduce their wow & flutter. Each year through the '80s my team developed many models such as the CT-A1, CT-A9, CT-91 and CT-93. By 1992 we released the ultimate cassette deck named Pioneer CT-95 or T-1100S for the Japanese market. Combined with my reference master mechanism, the newly developed Dolby S system, a precise automatic tape tuning system and many other improvements, the CT-95 won the highest ratings from various German hifi magazines. They felt that the CT-95 surpassed even the famous Nakamichi Dragon. This was my secret medal and private delight.