Spec RSA-V1 Integrated Amplifier REVIEW

July 20, 2012
10 mins read

$10,950 (Introductory price $9,700)

5 Stars

This obscure Japanese-made Class D amp is a velvet fist in a velvet glove

WHAT SOUND IS this? That’s the title of a song from the new Verlaines album Untimely Meditations, a rather strange track, yet one that I enjoy immensely. It’s also a question I found myself repeatedly asking about the Spec RSA-V1 integrated amplifier while trying to get to grips with its sonic characteristics.

This Japanese-made amp is something of an odd creation, conceived by a gentleman who spent a great deal of time working on single ended valve amplifiers using the mighty 300B valve. Sages tell us that sometimes a change is as good as a holiday, so out of left field, this guy designed a range of Class D amplifiers that sound nothing at all like you’d expect a Class D amplifier to sound. But more on that later.

Construction and Features

The RSA-V1 is a very good-looking piece of kit, with a restrained design aesthetic that speaks more of a grass roots company origin than a megacorporation. From a looks point of view, it could well have been built by any one of the many small UK-based audio companies, right down to those all too familiar Letraset style fonts on the front panel – but this approach is all part of the charm.

The satin silver chassis is nicely finished, and although the top and side panels are made with one piece of bent heavy gauge metal, the result is both solid and good looking. Internally, the various sections of the amp are isolated from each other with metal sheets. There’s a wooden bottom section that looks like a separate isolation platform but it’s very much attached to the amp, forming three footers. There’s more to this than meets the eye – the combination of wood and metal is a deliberate choice to reduce vibration. In fact, the wooden section is made up using multiple types of wood including solid oak from Hokkaido and Canadian sitka spruce. Even the three-point footer design is specifically made using harder solid wood to cut the transmission of external vibrations.

The Class D nature of the beast might lead one to expect a lightweight box mostly filled with air, a circuit board and a small switch-mode power supply. You’d be in for a shock, as I was when I collected the RSA-V1 from the local dealer, because the 15-kilogram weight indicates that there’s a substantial transformer in there, a shielded R-core unit to be precise. What the weight doesn’t tell you is that the designer uses reproduction NOS parts (copies of old oil capacitors recreated by Arizona Capacitors Inc, for example), ultra short signal paths and the highest specification PWM switching amplifier modules he could find – the same modules that are in the range topping Spec RSA-F1 amp.

The amplifier’s topology is interesting – according to the diagram below from the Spec website, it’s a dual-mono design, with the audio signal running into digital volume controls, then into the PWM controller and switching FETs before getting passed through a low pass filter consisting of a simple circuit made up of a toroidal coil, condenser and specifically ordered capacitors usually used in valve amps. The whole ensemble has been tweaked and fine-tuned by careful listening. Even the inbound power has been carefully attended to with selected high quality components in the power supply including newly developed ultrafast soft-recovery diodes and electrolytic capacitors specially designed for this amplifier.

This isn’t one of those 1000 watt into 4 Ohms Class D amps, rather it generates a reasonable 50 watts into 8 Ohms, which neatly doubles into 4 Ohms according to the manufacturer. So there’s enough power to drive most speakers easily unless they’re really inefficient power hungry hogs. There are four rhodium-plated line level inputs round back (three RCA and one balanced XLR) controlled by a chunky rotating knob on the front panel. The speaker binding posts are solid enough and there’s the obligatory IEC power socket, which promptly had my Nordost Shiva power cable plugged in, where it remained for the duration of the review.

The power switch is a very cool locking number that could easily be found on the instrument panel of a vintage aircraft. The big volume control is illuminated by a subtly glowing blue LED, which can be turned off. Beware the little switch that cuts out the LED: flick it up and it turns off the glow but a click down switches the RSA-V1 into its power amplifier mode, and if it’s getting a 2-volt signal from a CD player at that point, your speaker cones (and ears) may be less than impressed.

There’s no wireless remote control supplied but in an odd touch, there’s a socket round back that accepts a cable running to a huge, but lovingly crafted wooden receiver for the optional metal-bodied RSR-3 remote. There’s no phono stage, no DAC, no pre-amp outputs or sub outs and no headphone socket; this is a bare bones integrated amplifier sans frills, besides the audio quality that is, which as we’ll see, is quite something.

Sound Quality

So what sound is this? It doesn’t take long to recognise that there’s something very interesting happening here, but it does take a little longer to put the pieces of the puzzle together. Once I did I figured out exactly what I was hearing – this is a Naim power amp aspirated by a very good valve preamplifier, with only the best aspects of both making it through this uncommon but oh so blessed union.

There’s no English page on the Spec website for the RSA-V1 amplifier but there is one for the similar looking flagship RSA-F1 model. That page, along with some dogged persistence with Google Translate got me the gist of the manufacturer’s attitude to audio, which basically comes down to exactly what I heard, the “natural and beautiful tone of a tube amp, the driving force of the semiconductor amplifier”. I just didn’t expect it to be quite this good.

There’s the same foot-tapping immediacy and pace that one gets with Naim gear, so listening to the RSA-V1 without getting deeply involved is tough. In fact, forget tapping feet, it got me off my feet more than once. [You levitated? – Sarcastic Ed]. However, beyond the speed grip, and intensity, there’s barely a hint of solid-state character here. Instead, you get a midrange that can only be described as liquid in the sense that’s usually only seen in valve amps. It’s not overly warm, nor does it drown the music in cloying syrupy sweetness, but it is fluid, effortless and so suave as to defy the Class D or PWM origins of the signal.

I had the same Living Voice Avatar II floorstanding speakers that I used for the Shindo review (as seen here) and they proved an excellent match for the RSA-V1, and along with my Marantz SA-8260 SACD player and a cryogenically treated Slinkylinks cable loom and Nordost power cables, the sound was a beguiling combination of fire and silky smoothness that suited pretty much all kinds of music.

Cue up the mellow stylings of ‘House of Valparaíso’ from Calexico’s superb Carried to Dust album of 2008 and the sound is simply entrancing. The speed of the instruments in the intro is sharply noticeable, the percussion sounds like it’s coming from the hollow depths of an actual drum kit thanks to the abundance of textural information on offer, and the vocals come across like they’re being reproduced by some kind of magical smoothness generator powered by 21-year- old single malt Scotch. Instruments are nicely separated in the mix and the dynamic range is extended, with an easy sense of scale.

Switch to ‘Karmacoma’ from Massive Attack’s Protection and the RSA-V1 has the vocals placed dead centre and well behind the speakers with that commanding bass line throbbing out into the room. Here the Living Voice speakers deliver more bass weight and impact than they did with the Shindo pre/power combination in front of them but the bottom octave is still AWOL, as expected from the frequency extension figures. However, what is there is taut and locked down with no looseness. The overall quality of the bass is very good, and while I’ve seen feedback in other reviews stating that the bass seemed a little homogenised, I had minimal reservations, except perhaps that the midrange is so fabulous that it could well be seen to be making the bass seem less nuanced.

I worked through much of ZZ Top’s Six Pack compilation via the Spec and while this recording has been criticised as lacking in bass quality compared to the original releases, the RSA-V1/Living Voice pairing made it a lot of fun – I’d spin that big volume knob to about one o’clock and settle in for a long session with Gibbons, Hill and Beard, loving the big sound of tracks like ‘El Diablo’, where the bite and distortion of the guitars sound much like I’d imagine the guitar amps to sound in the first place. This is another track where the head-nodding and foot- tapping is mandatory if you’re alive; if there’s no movement, then you may have a rather serious problem.

Incidentally, with these 94dB sensitive speakers, one o’clock on the volume knob is all I ever needed (or wanted), even in a big room. The RSA-V1’s sound is so crisp and clean, with a low noise floor that it always sounds quieter than it actually is. It’s only when I wandered downstairs and heard just how loud the music upstairs was that I twigged how clear and easy the RSA-V1 is to listen to.

I occasionally thought that I was being taken for a ride by an evil conspiracy, that the silver-tongued and totally unfatiguing top end just had to come from valves, along with the midrange, but that’s not the case. This system is beautifully balanced right to the very top, especially with the help of that rather nice silk tweeter in the Avatar II’s. Cymbals rattle and crash off into the far end of the audible spectrum with nary a trace of harshness and zero roll off, just effortless extension. Allied to that midrange, it’s a pleasure that demands more and more listening time.

Wild Beasts’ ‘The Fun Powder Plot’ from the epic Two Dancers album was a track I had to hear through the RSA-V1. With my turntable out of action, I pressed the 320kbps download that came with the vinyl into service via my iPod Classic and Pro-Ject Dock Box Fi iPod dock. Result? Hell yes! My listening note is short and sweet: “Bloody marvelous!” The speed of the drumming here is magic, the falsetto vocals strong, sweet and packed with reams of detail and textural touches not heard on lesser systems. All in all, this is something close to brilliant, especially via this humble source. The terrible cliché of pace, rhythm and timing just has to be invoked here, because the amp emulates the original hero of that realm (Naim) but adds an entirely new level of refinement and enjoyment.

Detail levels are very high, courtesy of that low noise floor no doubt, but the RSA-V1 is just one of those amps that cuts a layer or two (perhaps three) of grime from the performance, sounding high res but not like typical hi-fi – the lovely valve-like sound elevates it beyond that. Soundstaging and imaging are unfailingly precise, with a real sense of depth behind the plane of the speakers and tight control of the placement of performers and instruments. Funnily enough, the soundstage height was somewhat taller than when I had the Shindo gear in place.

My only quibble with the RSA-V1 is that it needs a bit of a warm up before it can be heard at its most stunning, which is ironic as it runs as cool as any amplifier I’ve ever used – after hours of use, there’s no heat in the chassis at all, just a faint warmth around the power switch on the front panel. Still, it starts off sounding good but marginally lean, but after half an hour or so, the midrange warms up just a tad and the balance is perfect. No big deal, many amps display the same characteristic but it’s worth noting.


What then of the question I asked in the beginning of this review: “What sound is this?” Listening to the dissonant yet bizarrely enjoyable Verlaines track on this amplifier is an experience. I’m usually tempted to turn it down on other systems and especially on headphones because of the merciless rasp of the horns but here, it’s a roller-coaster excursion into alien territory at high volume, and it’s a great deal of fun. The harshness vanishes, but not because the RSA-V1 is plastering over the cracks, it’s just such a smooth yet insightful amp with something of a unique sound that seems to make me reach for more volume, not less.

It’s versatile too. I tried everything from Eminem to Tony Joe White, and Diana Krall to Nirvana on this system and never felt inclined to hit the skip button because the amp wasn’t doing justice to the music. Quite the opposite actually – CD goes in, CD plays to the end. If I had to make a call, I’d say that the quality of the midrange marginally flatters the kind of acoustic music I like more than it does hard rock or rap but not to a degree that would worry me, because the pace and speed keep the RSA-V1 honest with harder music.

I mentioned the thought of being taken for a ride, that there had to be valves under the hood. At times I wondered if I’d see a Naim power amp stashed in there too if I cracked the hood. This ongoing comparison to both Naim kit and to high-end valve gear is high praise – the Naim sound is one I like a lot but it can be a bit lean and dry at times, particularly with the wrong speakers in the loop. The Spec RSA-V1 gives the best of both worlds with none of the negatives, bar perhaps a lack of outright power, but then again, neither valve amps nor Naim amps are known for big power, except for a few high-end valve monsters. This sounds like a hybrid amp of note, despite not really being a hybrid at all.

You don’t get many of the bells and whistles that feature on a lot of modern integrated amplifiers but this is an addictive stereo component. The rarity of the brand, and the idiosyncratic construction and architecture make it a genuinely interesting proposition, but the superb sonics make it an entirely compelling piece of high-end hi-fi gear.

It does everything the designer intended it to do and it does it all well. It’s no modern efficient Class D wonder, pumping out enough iron fisted grunt to drive even a set of Apogee panel speakers within an inch of their lives; rather it’s a far more subtle offering, a velvet fist in a velvet glove if you like, but with real strength in its grip. This isn’t a criticism – matched to the right speakers, the RSA-V1 can more than hold its head up alongside its competitors at this lofty price point. It’s obscure, eccentric, scarce and totally worth a listen if you’ve got around ten gorillas to spend on a high-quality amplifier. It really deserves some matching equipment that’s at least as talented, so don’t be shy when you’re putting a system together around it. You won’t be sorry. ASHLEY KRAMER

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