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Srajan Ebaen
Financial Interests: click here
27" iMac with 3.4GHz quad-core Intel Core i7, 16GB 1.333MHz RAM, 2TB hard disc, 256GB SSD drive, ADM Radeon HD 6970M with 2GB of GDDR5 memory, PureMusic 1.89g in hybrid memory play with pre-allocated RAM and AIFF files up to 24/192; Audirvana 1.4.6 in Integer mode 1, Metrum Hex, AURALic Vega, SOtM dX-USB HD with Super-clock upgrade & mBPS-d2
Preamp/Integrated: Nagra Jazz, Esoteric C-03, Bent Audio Tap-X, Crayon Audio CFA-1.2, Gato Audio DIA-250 [on review]
: First Watt SIT1, Goldmund/Job 225, AURALiC Merak [on loan]
Speakers: soundkaos Wave 40, Zu Submission, Boenicke Audio B10, German Physiks HRS-120, AudioSolutions Rhapsody 200
Cables: Complete loom of Zu Audio Event,
KingRex uCraft USB cable, Zu split USB cable, Van den Hul AES/EBU cable, Tombo Trøn S/PDIF cable
Artesania Audio Exotyeric for front end, Rajasthani hardwood rack for amps
Powerline conditioning: GigaWatt PF2
+ Vibex Two 1R on amps, Vibex Three 11R on front-end stack

Sundry accessories: Extensive use of Acoustic System Resonators, noise filters and phase inverters
Room size: 5m x 11.5m W x D, 2.6m ceiling with exposed wooden cross beams every 60cm, plaster over brick walls, suspended wood floor with Tatami-type throw rugs. The listening space opens into the second storey via a staircase and the kitchen/dining room are behind the main listening chair. The latter is thus positioned in the middle of this open floor plan without the usual nearby back wall.
Review component retail: €9.500/$12.000, €900/$1.200 for the optional RSR-3 remote control module

When a designer traces his audiophile lineage back some 38 years—to when Jean Hiraga first imported NOS tubes to Japan to promptly build himself a DA30-based SET with WE310A driver/274B rectifier followed by a vintage hornspeaker system based on Altec 414A woofers, Onken OS-500MT mid/high drivers and matching SC-500 wooden horns—you just know his sonic north. When such a designer worked at Teac on their open-reel recorders as mechanical engineer and subsequently for nearly two decades at Pioneer where he was involved with more tape decks—the Nakamichi dragon-slaying CT-95 was a highlight—and the world's first true universal player whilst continuously evolving/upgrading his original SET... then you also know that despite newfangled technologies a love of vintage tube sound remained alive throughout.

When Shirokazu Yazaki joined forces with International Rectifier engineer Tsutomu Banno to launch SPEC Corp. on February 6th 2010, he had a most contrarious notion. He meant to advance his beloved valve sound with the very latest in ultra-efficient super high-speed switching power Mosfets which Banno had helped develop during his IR tenure. Yazaki-San is adamant that class D circuits are particularly vulnerable to the quality of their power supply and low-pass filter. With him the former becomes a massively overbuilt linear affair, the latter an ultra-simple inductor/cap circuit albeit based on rare custom parts. "By the end of 2009 I had reached the conclusion that the best capacitor to use in such a filter was the vintage oil-filled type marked 'hermetic seal' from West Cap, part N° CPV09 0.47/600 made for the US military in 1967. It turned out that the original capacitor manufacturer had survived in Tucson, Arizona. In the early 90s they'd changed their name to Arizona Capacitors Inc and from West Cap taken over huge production facilities and endless engineering drawings. As their Japanese distributor since the summer of 2011 we've worked closely with Arizona Capacitors to sell their quality custom oil-filled capacitors in our domestic market. We were thus able to adopt their fantastic capacitors for all our amplifiers. If I were to isolate something very important about the true potential of D-class amplifiers, it's how they control the inevitable back electromotive force from the speakers. In D-class amplifier the current of the back EMF is directed back at the power supply, not the feedback loop of traditional transistor amps where it undermines their phase integrity with dynamic music signal."

"The ultimate performance of a class D amp also depends on just how accurately it implements its pulse-width modulation switching. Here International Rectifier's DirectFet output device with a high-voltage invariant IC driver of excellent time axis performance really establishes new parameters. Other well-known class D advances are almost triple the efficiency of conventional semiconductor amps; instant current delivery; bidirectional energy transfer to regenerate back-electromotive forces in the power supply; and excellent linearity."

In the SPEC book this makes class D a 3rd-generation proposition preceded by the 1st generation of tube amps which were natural and rich of tone but of limited bandwidth and incapable of driving modern low-efficiency speakers; and the 2nd generation of traditional transistor amps which had high power, certain disadvantages based on their implementation of negative feedback plus wasteful energy consumption. Done right they believe that class D can combine the very organic presentation of tube amps with the raw drive power of transistor amps to become a best-of-both-worlds hybrid.

The use of specific tone woods for SPEC's metal enclosure plinth reminds us. Yazaki-San's audio background began in mechanical engineering. Just like his deliberate exploitation of NOS-type capacitor sonics*, this indicates strategic voicing or circuit tuning.

* SPEC's mica capacitors are exotic as well. Their dielectric is a muscovite-type precious mineral with an extremely stable temperature coefficient and excellent dielectric voltage strength. Their MC-DA Series caps employ ruby mica of the highest quality produced near Giridih/india. They're built with laminated construction to minimize inductance so capacitance doesn't change until the MHz band. Silver-pasted electrodes are imprinted on both sides of the mica sheet. To avoid any magnetic material, the metal holder locking down the laminated dielectric is made of tin-plated brass plates. The capacitor body is finally sealed in epoxy resin to minimize internal self resonance when applied voltage energizes the inductor material and electrodes. SPEC's favored diodes meanwhile are of the very hi-tech SiC or silicone carbide type.

As such SPEC's approach to class D differs from Hypex/Ncore's Bruno Putzeys whose own blog contains comments like "...the fly in the ointment came as I slid our preamp proto (later baptized Makua) into a rack for one such demo. To understand my befuddlement you ought to know that said rack space had just been vacated by what I’d call a glorified variac but what was probably an 'autoformer-based passive preamplifier'. It had two big knobs, one for source (three positions) and one for gain (twenty-four 2dB steps). Rotating them took considerable force and both went alarmingly clunk as one did so. It was in other words esoteric. And its distributor had just asked me whether Makua had a remote control. Here’s the mistake I made not including one. When a product looks like it’s been designed in a basement decked out with Buddhist paraphernalia and the electrical circuitry—such as it may contain—is a highly intimate statement of one’s most personal artistic genius, nobody asks for a remote control. One doesn’t question High Art and demand that it be practical. But as soon as some degree of engineering is evident like the presence of an actual gain stage or the absence of distortion, the product becomes pedestrian and it’ll have to use the zebra crossing like anyone else."

The RSA-M3EX integrated combines the esoteric—tuned wood footers, tonewood plinth, vintage-style oil-filled caps—then crosses the zebra stripes with an optional costly remote executed differently once again as a wired wooden receiver box. That separation keeps this circuit and its potentially noisy display completely isolated from the main box. It also means that someone not into remote volume needn't pay for it.