Accuphase A-70 User Manual

Hifi & records – 01/2015

Continuity

Test: power amp Accuphase A-70

Perfect technology-transfer: the A-70 profits strongly from the innovations, which

Accuphase developed with the Mono blocks from A-200.

The age of information doesn’t just cause enthusiasm but also in some places discomfort. Hence the
technical progress isn’t much different from the Euro. There is so much what was yesterday’s matter
of fact is suddenly called into question. But from the hard times, which people like to forget a bout,
was already the talk even before the Lehman-bankruptcy and the sovereign debt crisis. What remains
after all this is the vague feeling, that there is something wrong – when tectonic shifts cause the floor
under one’s feet to move, it is easy to lose footing.

Even the High Fidelity is currently being completely revised. Therefore, don’t we as well need
dependable light houses to show us the way? Institutions, that preserve the high end spirit instead of
exploit it, who don’t follow every trend , stand for something and have proven this on more than one
occasion. Those are admittedly rare, but there is one name that comes to mind: Accuphase.

That is less because of the tradition of the machines with the champagne colored fronts, but more
because of the continuity, which Accuphase demonstrates daily. This continuity is rooted in the
permanent strive for improvement, the imploring effort to offer the customer an even better equivalent.

In the colorful market nowadays such a mindset is anything but self-evident. Probably the social
education worker Mr. Gmeiner is right: ”Everything big in our world only happens, because someone
does more than he or she must.”

Accuphase has in the last years presented a complete line of reference-products, sinfully expensive,
but also absolutely fantastic. The end of the line is made of the class-A mono blocks A-200 (Magazine
2/2013), with which Accuphase has made again a decisive step forward. The nice thing about such for
us average mortals “unreachable” products is that they act indeed as technological-godfathers in
Yokohama and not only on paper: the A-200 monos delivered the exact blueprint for the revision of
the Stereo-poweramp A-65 to A-70.

Even their predecessors already counted to the Accuphase classics par excellence, which considerably
contributed to making the class-A-technique through perfect operating reliability completely socially
acceptable. The round dance was opened by the A-50 in the year of 1993. Since then Japan’s big class­A-Stereo-power amp has every five years been revised and refined. Not only in the technical
department but also the appearance has progressed. The A-65 and the new A-70 are instead almost
identical. Also the fundamental amplifying concept is the same: 10 pairs Mosfet-Endtransistors
(K3497 and J618) provide full capacity, on their side is a central organized, capsuled toroidal­transformer and two large Elkos with unchanged 82.000 Mikrofarad capacity each. The class-A
section lies still at 60 Watt at eight Ohm, from this current feedback Accuphase promises itself a
highly accurate phase.

New is with A-200 incorporated “Gain-Management” which means: Which section amplifies how
much, how does one distribute the work for the input and capacity amplifying levels? Accuphase used
to incorporate very classic comparable amplifying factors, 12 dB in the input, 16 dB in the output. But

the Japanese realized that it is sensible to relieve the output stage from the current amplification,
because the input amplifier is more suited to this cause. This input amplifier can now in the A-70
contribute 22 dB to the total amplification, the output section merely 6 dB. Accuphase wants to even
further diminish the noise floor of the already very quiet A-65. With the A-200 the Japanese have
tackled a topic, which was earlier called the Archille’s heel of their power amplifiers: the damping
factor.

Operating reliability is priority in Yokohama, which is why Accuphase always had a relay in the
speaker output. Just in case for all possible situations, or even the worst possible situation, the
accidental short-circuit through the careless owner. Such a relay is anything but ideal for the internal
resistance and when the coil of the Boucheron-link in the output makes its process dependent on the
frequency, then the damping factor is neither high nor linear. Therefore there are no more relays in the
A-70 protective circuit, but modern electric Mosfet switches. Furthermore, the producers looked out
for as large cross sections as possible in the signal path, for example with the thick flat-wire-spool.
With the now reached damping factor of 800 that is double that of the A-65, the topic should be once
and for all closed.

Just like its predecessors the A-70 belongs to the all-rounders of the power amp-line and the
equipment leaves no wishes unfulfilled. The input is switchable from symmetrical to asymmetrical and
one can even select the XLR-Pin-allocation via a slide switch. For the amplification there are four
levels to choose from max./ -3/ -6/ -12 dB. Three operating methods are possible: the normal stereo
input, >>Dual Mono<< for bi-amping and the performance-enhancing bridge input, which more or
less represents the exception. The large loudspeaker clamps for bi-wiring are available twice.

Typica l for Acc uphase are the perfectly made performance indications, with bars for the decibel and
numerical Watt display, which one can view on its own or both at once. One can even turn off all of
them, but the whole things is optically so very discreet that one has no desire to do so. The
measurement covers three switchable performance parts up to 10/100/1000 Watt and is highly precise;
the difference to our UPV-Analyzer in our lab (which costs double as the A-70) lies in the first
measurement range in the hundredth, in the second range at one to two one-tenth and even at full
capacity at about one Watt, meaning less than 0.5 percent.

For the test we received next to the A-70 also a preamp, C-3800 and the CD/SACD-Player DP-720,
the power supply PS-520 for source and preamp is already present in our studio. Similar to the A-65
Test (Magazine 4/2010) the loudspeaker partner was a Magico V2, the wiring was conducted via
Accuphase-cables and HMS Gran Finale Jubilee. We gave the set up ample time for warm up and play
practice, which can truly take a couple of days.

The Accuphase-trio then played constantly: very cult ivated, wonder fully balanced, in harmony with
itself. The control of the >>big Power Amp<< was apparent, which radiated sovereignty, had color,
without artificial beautification. The once slightly roundly-soft character of the A-50 has its followers,
I know, but I wouldn’t miss it for a second. And even without a direct comparison with an A-65, I
tentatively hypothesize that the A-70 objectively makes everything a touch better – that she has
without a doubt inherited from the A-200. Within the set up so that we could place the position of the
A-70 we even exchanged the power amps, herein I was especially curious about a comparison: how
my A-20V from the year 2000 would hold up. That the A-20V has a lower output, was something we
tried to our best to keep in mind and therefore selected a musical program which wouldn’t demand
more than two to three Watt – this was for both power amps truly a very easy exercise. Still the A-70
continued to show a little more stability, seemed more mature – this was supposed to be expected. But
that she also plays way more precise, especially in the high notes, and simultaneously appear less