Complete review in LP magazine (Germany), Issue 06/2011

Accuphase MC Phono Cartridge AC-5 and Stereo Phono Amplifier C-27

Bubbly Moodby Holger Barske
If this is not a good reason for celebration: the Japanese manufacturer
Accuphase, whom we already considered a bit lost for the analogue cause, hasreturned with an impressive plea for vinyl. And the brand-new MC pick-up is avery particular comeback.
When we speak about pick-ups, it’s not really so that the AC-5 is the firstmighty deed of the engineers from Yokohama. Accuphase has built one dubbed AC-1
already in 1979 which was later followed by the AC-2 and AC-3. As is known, theAsians are not very fond of the number “4”. Hence, the AC-5 is at least a logic stepwith respect to nomenclature. Not so long ago such a product would have been
regarded a veritable sensation, in particular if one is aware that over the years
Accuphase has fully set its priorities on digital sources. Well, there were and arededicated phono boards to be optionally employed in various pre- and integrated
amplifiers from this maker, yet the focus was apparently somewhere else: Accuphase
was and still is one of the most fervent advocates of SACD. However, as theacquisition of foreign high-quality CD/SACD drive mechanisms became more andmore problematic, Accuphase eventually decided to have them developed and built
in-house. These proprietary drives were then to be employed in various integrated
SACD/CD players and a drive/converter combination which to this date haveaccomplished an excellent reputation all over the world.
Yet Accuphase wouldn’t be the enterprise it is, namely one driven by music
enthusiasts, had it lost sight of the analogue profession. Not so long ago, Accuphaselaunched the phono amplifier C-27 which has already received quite a favourable
acceptance in the market. It goes without saying that the next logical step was tocomplement this amp with a new pick-up cartridge and therefore it made sense to us
having both reviewed in one go.
The AC-5 is a moving-coil pick-up in the classic sense. The distinctive features
however begin already with the choice of materials for making the body: Pewter is analloy consisting of tin, antimony and copper and it is said to have excellent damping
properties. The mounting plate has been furnished with an additional layer of rhodium
and the main body with a layer of gold. In view of the rather heavy “buildingmaterials” I was actually a bit astonished to see the moderate weight of merely
11.5 grams. Still, this figure puts the AC-5 into the average “weight range” of what
one is to get these days.
Another characteristic is the boron cantilever. Well, other makers are also
employing boron at this point, however quite commonly the crystalline variety thereof.
The cantilever used by Accuphase is made of solid amorphous boron. Apart from theextremely high inherent propagation velocity, amorphous boron also offers a1

considerably enhanced rigidity as opposed to crystalline boron. The renowned
Japanese specialist Namiki supplies the diamond stylus with “Microridge” cut of
which the tiny bottom radius takes care of its precise tracking deep in the grooves.
The wedge-shaped design of the stylus also guarantees a rather long service life. Asto the arrangement of the coils inside, the goal was to design the best possible
symmetry in order have identical signal currents - and thus sonic balance - generated
by the coils for the left and right channel. For the coils Accuphase decided to go forvery pure, oxygen-free, long-crystal copper wire with merely 0.003 mm in diameter.
Despite of the low internal impedance of 4.5 ohm, a fairly high output voltage of
0.24 mV (at 1 kHz, 5 cm/sec) could be achieved.
A glance at the damping array is also quite interesting. It consists of synthetic
rubber in a circular arrangement whereby the ring is radially divided into eight equally
sized segments. According to Accuphase this construction is to ensure a quick
response to vibration velocity changes and to neutralise elastic deformation stressbetween the channels. As to the material of the magnets we learn that noble
Samarium has been employed, however a variety with an inherently very high Curie
temperature of 700 to 800 °C. This is said to have excellent thermal characteristics
also at normal, i.e. room temperatures. So, let’s recall our school classes in physics:the Curie temperature of a magnetic material is the one above which the material is
to lose its magnetism.
Owing to the body’s clear shape and straight edges the AC-5 is easy to mount.
Its weight and compliance of 12-15 mm/N suggest the use of medium-heavy pick-up
arms which however are common standard these days. But this is actually not reallyan issue to worry about because MC cartridges are generally rather forgiving in thisrespect. Personally, I would have appreciated a colour-coding of the output pins
because I usually fail to remember their correct polarity. Nevertheless, the supplied
instructions will in any case assist you to connect them properly.
As far as I know the C-27 is the first “real” external phono amplifier fromAccuphase. In the past, there was indeed an MC pre-preamplifier from this makerwhich however was still to require an MM phono-equaliser input stage to make it acomplete phono amplification section. Now, the C-27 is embracing all this in one
cabinet, like quite a few other such devices being offered today.
In the best of Accuphase tradition the C-27 is an absolute feast for the eyes. It’s builtwith artisan perfection that hardly any other manufacturer can keep up with. I think
there really is no alternative to the champagne-coloured front and the deeply grained,
polished wooden side panels. It goes without saying that a component fromAccuphase must look exactly like that because otherwise it would be an unjustifiable
clashing with the style.
The C-27 comes equipped with unbalanced RCA inputs whereas the outputs
are configured with both RCA and XLR connectors. The latter are provided with afacility to switch absolute phase, respectively polarity – worthy of praise! Up to three
pick-up cartridges may be connected and a smart memory inside for each input is tostore and recall the pre-set parameters. These are numerous indeed, namely MM orMC operation, two gain stages and various input impedances: 1, 47 and 100 kilohm
for MMs, respectively 3, 10, 30, 100, 300 and 1000 ohm for MCs. The input capacityfor MM pick-ups is evidently fixed, however I have found no information as to its
value. What eventually remains is a switchable subsonic filter with a slope of -12 dB2per octave and which comes into effect below 10 Hz. Pre-setting of all parameters isdone the classic way, namely by means of rotary switches and pushbuttons. As far as
I’m concerned, it’s very nice to see that it was feasible to get access to the memory
functions also via traditional operating elements. To fumble around with arrow keys
through a menu has thus become dispensable. For this reason the C-27 also doesn’t
need the respective monitor but resorts to a dark glass display on the front panel
behind which LEDs are indicating the effective operating status.
The inside of the amp is dominated by plenty of power stage and not quite asmuch phono amplification – at least with respect to the surface area. Two
encapsulated and absolutely silent toroidal power transformers, which have been
positioned with due respect to the signal amplification, are taking care of the electricenergy for this Beauty. In the centre we see the board for voltage supply andregulation in a dual-channel layout and equipped with beefy filtering capacitors. Theright section holds the actual amplification/equalisation board. A closer look however
reveals that there are in fact two circuit boards arranged one above the other, and forwhich the material Teflon® (® of DuPont/USA) seemed to be just good enough.
The apparently enormous circuit complexity can be explained quite simply:
Accuphase has provided two fully independent amplification/equalisation circuitries
each for MC and MM pick-up cartridges. Usually, there is either just one amplification
stage of which the gain can be varied within a fairly wide range or a dedicated MM
amplification/equalisation circuitry to which an MC gain stage can be switched. But
completely separate stages? Well, to my knowledge no one else is offering this.
By all means, on closer examination the separation does make sense. MMcartridges need only low amplification. Usually, they’ve got a high internal resistivity
respectively impedance and they like to be combined with an amplifier stage that is inoptimal harmony with such a source and furthermore is generating noise as low aspossible. By comparison, MC cartridges not only deliver much lower voltages but
generally have also very low internal impedance. All this requires a completelydifferent approach with respect to the optimal circuitry for each pick-up principle. And
if one prefers to get by with a minimum of amplification stages then things can only
be done the way Accuphase is demonstrating here.
It is interesting to see that the circuitry of the MM section is slightly moreelaborate than the MC counterpart. While on the latter eight differential amplifiers
arranged in parallel-symmetrical configuration are responsible for the input
amplification, the MM board has got six of them, however with an additional buffer
stage consisting of FETs in – as Accuphase has dubbed it – 3-parallel configuration.
A wise decision as FETs can be considered the best solution for high-impedanceaudio sources, owing to their low-noise properties. Equalisation on both boards isdone via the negative feedback loop of the gain stage, which is likewise composed ofsingle transistors. Chips, i.e. integrated circuits, are allowed to take overcircumferential functions only. And then we spot a large number of relays of which thetask is to switch the various operating modes. In view of all this I think it’s superfluous
to mention that layout and construction of the circuitry inside the C-27 is once again afeast for the eyes of every electronics buff.
For the listening test I had the AC-5 initially loaded with an input impedance of
100 ohm whilst gain was set to “high”. Actually, that’s already all you need because
right from the beginning this Accuphase combination is beguiling you with a strikingly3smooth and silky rendition. It can well be argued if the AC-5 loaded with 300 ohm is atad more airy in the upper frequency range, yet I personally prefer its more stringent
and tighter pace at 100 ohm. The C-27 is an extremely transparent amplifierequaliser without any sonic “fingerprint” of its own. For this reason it has got theabsolutely perfect qualification for the AC-5. And, yes, the AC-5 is a wonderful moving
coil cartridge which in no case wants to run the risk of sounding like a typical MC
pick-up. It may perhaps do without the last bit of thundering dynamics in favour of an
integral and complete performance. I would also speak of a perfect sonic balance if
there wasn’t that remarkably “analogue” midrange. In this respect I would evenventure to say that as far as the rendition of male and female voices is concerned
there is hardly anything around to beat it because it gives singing voices an extra
boost of liveliness, expression and authenticity.
No question that an adequate companion is needed in order to fully achievethis. The C-27 however does recommend itself with distinction for exactly thispurpose. Up to now I have yet to detect dynamic or tonal shortcomings from thisamplifier as it is meticulously passing on what is delivered from the pick-up cartridgeat the input. No matter if this is displayed by the dynamic fireworks from Clearaudio’s
Goldfinger, the snap and vehemence from the MFSL-Miyabi or ultimately thestunning midrange of the AC-5.
Certainly, the Accuphase AC-5 will also satisfy you when it can play in combination
with other fine external phono amplifiers. However, if you are really interested in theAC-5 and do not audition it in combination with the C-27, you’d be subject to adefinite sin of omission.

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