Test LP 6/2015]
Accuphase Phono-preamp C-37

Plus Ten
With the C-37 Accuphase is presenting the next generation of their homemade phono preamps. Which gives rise to the question: what is yet tocome after the excellent C-27?

R

egarding signal sources the Japanese maker may well be regarded as a

specialist in digital technology out there – their current range offers no less than fivedifferent CD and SACD players –, but they never let the analog roots pass into
oblivion. And so, especially these days, an external high-class phono preamp is amust for the product portfolio.
For many years this job was taken care of by the C-27 with utmost sovereignty, andsince in the phono sector not every year will normally produce a technical revolution,
I was indeed a little surprised by the announcement of a successor. It didn’t seem tobe really necessary. The C-27 reveals no shortcomings that would have required
some touch-up.
The new model is called C-37. Preventively we’d like to add that this has nothing,absolutely nothing to do with a varnish of the same name, which has been usedsporadically to paint components for the purpose of sound improvement. For it comesfrom Austria and is hence as far away from the strict Japanese art of engineering asa phenomenon could possibly be.
Here’s the good news: the C-37 is even a bit lower priced than its precursor. Its list
price is 8,300 EUR, whereas the C-27 was finally priced at 9,500 EUR. This is a little
goody you won’t find often in that form.
Visually both devices don’t differ much at first sight. The controls and theirconfiguration remained the same, on the new one two pushbuttons are no longer
round, but angular shaped, and the input selector switch has slightly gained indiameter – nothing to write home about.
The rear side shows the same view: there are still three (RCA) inputs with separate
ground terminals, one unbalanced and one balanced output with switchable phasing.
Before this may sound a little too terse: an XLR output with switchable phasing?
Have you ever seen this in any other phono preamp in this big, fat world? Well, atleast I haven’t.
However: if nothing obvious is happening here, hopefully they just don’t want to sell
us old wine in new wineskins? Certainly not. The revolution took place in details andonly reveals itself upon unscrewing the device. As a matter of fact, the Accuphaseengineers completely overturned their proven design concept. The C-27 was
1characterized by totally independent gain stages for MM and MC signals from theinput to the output. While the rest of the world would design a phono stage of thebest possible quality for the MM signals, which are stronger by about the factor of ten,and then realize the extra decibels required for MCs by means of another upstream
gain stage that would be activated when needed, the Accuphase people did it just theother way round.
Thus far. Because in the C-37 we find the very same topology as it is also appliedelsewhere. So is this a totally incomprehensible step backward? Of course not. At
Accuphase such serious design changes never happen without a tangible reason.
And here it’s a simple one: with their topical configuration they succeeded in pushing
the already exemplarily low noise even a bit lower. This is certainly not important by
all means, yet sometimes it is: the C-37 amplifies by 70 decibels at the max andhence commends itself as a playing partner even for extremely low-output MCs; themarket holds indeed some exciting models in store which merely provide an output
voltage of an infinitesimal 90 microvolts.
Interestingly enough, perhaps the even bigger evolutionary step from the C-27 to theC-37 is not even mentioned by the manufacturer: the changeover from conventional
components to SMD technology. Almost all semiconductors used in the C-37 areaccommodated in tiny surface-mounted housings. Because it’s a fact that a radical
change is going on in electronics as far as these aspects are concerned:
for electronics pros classic in-hole components are about as up-to-date as vacuum
tubes. And exciting, trendy components are simply available as SMD versions today.
Of these ample use was made in the C-37. Like in the MC input stage with its circuit
layout of three power transistors connected in parallel per channel. Heavy-duty
semiconductors for eensy-weensy signals? This makes sense indeed, because acertain parameter (key word: low extrinsic base resistance) makes this type ofsemiconductor particularly suitable for highly noise-sensitive applications. Thefollowing MM gain stage bears again some structural resemblance with the one
already used in the C-27 and employs FET differential gain stages wired in parallel.
The equalization takes place actively and way back in the circuit, meaning thecorresponding network lies in the feedback loop of the final stage.
All the associated treasures are located neatly separated on two stacked circuitboards, one for each channel. Not just any circuit boards, but of extremely low-loss
teflon. Owing to SMD these boards could be made noticeably smaller than those of
the C-27, which is why the bigger part of the power supply also found sufficient spacein that part of the body. The pre-regulators sit in the next compartment further
towards the center, on the far left we see the exceedingly well dampened toroidaltransformers, one for each channel as customary.
The C-37 would not be a genuine Accuphase device if there wasn’t way more behindthe operating concept than meets the eye, too. A rotary switch allows to selectbetween the three inputs – sure thing. Not so self-evident is the fact that the device
will memorize all performed settings fully automatically and provide them again quite
naturally when the position is selected the next time. This goes even one step further,and here one will recognize again the almost fanatical propensity for perfection: whenswitching back and forth between MM and MC operation mode the device knows, ofcourse, which load impedance was chosen the last time. This is not of vital
importance, but it documents an attitude which I have deep respect for. Speaking of2

MM mode: here we have again three possible load impedances: 1, 47 and 100 kiloohms. Very laudable. For MCs one can choose between 3, 10, 30, 100, 300 and1000 ohms. Those who are proficient in mathematics will notice: a neatly graduatedlogarithmic scale. This is Accuphase perfection.
Did the C-37 step up to send the C-27 to retirement now? Not at all.
Both devices play in a league where ”better“ or ”worse “ occur in fields wherenuances reign. And in the absence of a C-27, I feel incapable of delivering verifiablestatements as to the sonic differences between the two, for the life of me. However,what I can tell you in my capacity as the owner of such a marvelous amplifier duo like
C-2420 and A-46 by the same manufacturer: these two have literally been waiting fora phono preamp from ”the family“. The C-37 snaps in so strikingly well into the overall
tonal result that the imaginary ”click“ will immediately make your hair stand on end.
Whatever I had been using before the C-2420 and no matter how good the resultsmay have been – only with the C-37 there’s consummate mellifluousness. Soundwise
this phono preamp is invisible to such a degree that the delicate, colorful and utterly
elegant Accuphase sound soars to full bloom. Character? Not a trace. What you hearis the downstream chain and the music you’ll put on. What else should a phono
preamp be able to deliver?
Holger Barske3