[English Translation Test Accuphase A-250 / Hifi & records 04(Oct/Nov)/2018]

Tour de Force
Accuphase has meticulously refined their class-A mono blocks. What added value dothe new A-250s offer?

No, I can’t stop myself from pushing the central »Power« button though not even thecables are connected yet. Then comes that full-bodied »clicking« sound! Sure, this is
only a tiny, but nonetheless fascinating jigsaw piece of the demanding Accuphase
universe, where great emphasis is put on manual-technical precision. The value ofan Accuphase device can undoubtedly be grasped with the unaided eye. Conversely,
the manufacturing quality of many other components, which are labeled as »highend«, appears to be downright ridiculous. Of course, there’s a concept behind it,
because nothing will come from nothing. As Accuphase President Hideharu Itoexplains, other makers like to see their failure rates in the single-digit percentage
range, but he reverses that point of view: whenever an Accuphase customer has tocomplain about a failure of his gear, this is 100 per cent. Such is defined the ambition
to exercise ultimate precision in the production process, and each device isthoroughly tested in the Japanese city of Yokohama.
Likewise the German distributor PIA is well-reputed for leaving nothing to chance.
Therefore we didn’t only receive the new A-250 mono amps for a review, but once
again a complete Accuphase chain (DP-950 CD/SACD player, DC-950 D/A converter,C-3850 preamp). The »system idea« behind it has been cultivated for many years by
Accuphase and PIA, and so I may speak of a grown tradition here as well. The A-250
mono power amps are the evolution of the A-200 (see issue 2/2013), a class-A
design which had already been taken to the limit and the refinement of which has
now consistently been pursued. Developments at Accuphase take place similar to
the growing of a tree: little by little it keeps getting higher and higher. This refers
primarily to the technical, objectively measurable advances which, however, are only
implemented if the innovation is also reflected in the sound image. Continuity is thus
maintained and nothing well-established is abandoned.
The most important starting points for the previous Accuphase amplifier generations
were routinely the signal-to-noise ratios and also the damping factor. For the latter
the Japanese carefully examined everything that follows after the power transistors:
protection circuits, output relays, in fact every contact which could get in the way ofthe output section’s internal resistance. For the A-250 Accuphase gives a damping
factor value of 1,400, but only 1,000 is officially stated, just like with the A-200 which
had already set a new lab benchmark with its excellent signal-to-noise ratios.
Between ourselves, even Wilfried Kress had been wondering how Accuphase would
want to exceed these one more time, but after the measurements he confirmed that
the A-250 had seized the crown.

Regarding the output power, the A-250 is equal to its predecessor. Here and there
the basis is a mighty toroidal transformer, flanked by two filtering caps with 100,000
microfarads of capacitance each. The highest form of construction meticulousness,
which is aimed to transport the signal with as few losses as possible and to keep itaway from any interference, becomes apparent in fluorocarbon resin coated GFRP
printed boards with a low dielectric constant. For the input stage no less than fourcircuits are wired in parallel to form a dual »MCS+« (Multiple Circuit Summing) layout.
I hardly want to imagine with how much expenditure of time the design engineers at
the Accuphase research lab are meanwhile struggling for every decibel of S/N ratio.
As with its predecessor, 40 Mosfet transistors, which are wired in parallel anddevided into two units with their own heatsinks for heat removal, deliver the outputpower. The increased damping factor achieved in this output stage should be audible.
Upon leaving the A-250, the amplified signal sees one of the most solid connection
terminals I’ve ever witnessed and whose brass core is gold-plated against corrosion.
Due to the high tightening torque the use of spades suggests itself. Owners of biwiring cables will be happy with this dual layout.
The visually striking display elements were redesigned by Accuphase for the A-250.
The LEDs are now bigger and easier to read. The numerical power indicator nowoffers an »auto range« function where the decimal point automatically floats with therespective output power. What sets Accuphase apart from many competitors even inthis point is revealed in the lab: the power specs determined with our R&S UPV
analyzer differ from those displayed by the A-250 by less than one per cent. Hence at
10 watts into four ohms by less than one tenth of a watt! In practice one can evencheck the flawless function of loudspeakers with such a precision instrument.
The A-250 are optionally fed through RCA or – more recommendable – XLR cables.
Input switching is done on the front panel after the massive flap has opened at thetouch of a button (see fig. above left). Here you can set the gain factor in four steps
and also switch the meter functions of the power indicator.
But now the accurate A-250 bargraphs shall at last dance to the beat of the music. I
had asked HMS to send me the missing Suprema XLR cables, which I gave a lot of
break-in time. Although I hadn’t moved the KEF Reference 5 by one inch, the firstnotes from the Accuphase system already surprise me deeply. For the first minutesof Tchaikovski’s »Swan Lake« turn out to be a revelation. Owing to the A-250 monosat the end, the whole Accuphase chain exudes an enormous tranquility and stability.
However, such an – actually desirable – sovereignty also bears the risk to create a
distance between the music and the listener. Not so with the A-250s, au contraire;
here a »gentleness that veils the instruments« can be noticed which I respond to in
the most positive way and which hits me quite unexpectedly. Conversely one mightalso say that the sound image has no trace of cloudiness, there are no stressful
passages – heavenly conditions for natural instruments and voices, I can’t find anyother words to express it.
Who takes the time to listen completely through Beethoven’s »Missa Solemnis« willsense the wonderful energy of this music. However, only individual aspects willremain of it if the sound system mixes solo voices, choir and orchestra into a tonalsmoothie. What the Accuphase mono blocks deliver here is phenomenal. First of all
they reproduce the size of the recording room flawlessly; the timbres of theinstruments, the clarity of the choir and of the soloists sitting in front of it, they are soclose to a live experience that the emotions caused by the music are equal. It may
seem paradoxical, but this doesn’t sound like »amplified music« at all.
These positive qualities also benefit the music of saxophonist Kamasi Washington.
Intelligent jazz arrangements characterize his compositions that alternate with thegreatest of ease between simplicity and complexity. While the shiny golden chain
sends the listener onto a journey, an integrated amplifier we’ve brought in for acrosscheck tears the musical events apart almost beyond recognition. In the lattercase I even dare ask why I’m listening to this »noise« at all. On the other hand, with
the A-250s I’m living one exciting moment after the other.
Likewise, the rendition of Neil Diamond’s »Hot August Night III« also seems to be notof this world. Of course, it’s not only the sound quality of this live recording thatmatters, but the atmosphere and the realistic access to the vibes of this concert, andhere the mono blocks develop a magical attraction.
Now I really want to know what’s up and first swap the source followed by thepreamp. Both steps I perceive as a clear sonic downgrade. First the tonal
expressiveness and hues get lost, the sound is paler now and more anemic. With theC-3850 missing as well, not much of the sound image is left. Chastened I therefore
quickly return again to the complete Accuphase chain.
In an awe-inspiring manner the Accuphase quintet says goodbye with Beethoven’s
piano concerto no. 5. Christian Zacharias has taken his seat at the grand piano, he isaccompanied by the Dresdner Staatskapelle under the baton of Hans Vonk. From thevery beginning his fingers are flying over the keys of the grand piano which, pictured
in its true dimensions, stands in the middle of the stereo basis. With the joining of thestrings the picture becomes by no means smaller; instead the room behind thespeakers opens up, no, it tears open. And here, too, the A-250s prove to be mastersof a detailed reproduction which is not sober, but comes along with a gracefulness
that only benefits the work. Already now, while the final chord is fading, I miss thishighly cultivated reproduction.
Accuphase masters an essentially insurmountable hurdle: the new A-250 mono
blocks are both technically and soundwise a blockbuster. The extent of a cultivatedand at the same time precise reproduction by this class-A design is unprecedented.
Speaking of art with regard to the external and internal workmanship is a matter offact for the Japanese. With the A-250s Accuphase once more sets new standards.
Olaf Sturm