Review in AUDIO magazine (Germany), March 2006
Accuphase Integrated Amplifier E-550

Precision Jobby Joachim Pfeiffer

The biggest and dearest integrated amplifier by Accuphase tested exclusively
in AUDIO.
Not really a big surprise on the first sight. The new integrated flagship fromAccuphase, the E-550, comes just slightly higher and a tad less wider than its alreadylegendary predecessor E-530. The formerly rather matt side-cheeks are showing
high-gloss now, and - I'm sure you'll be pleased to read this - its retail price has comedown by an enjoyable margin! Well, the new model does not look really new and theold one not really old. So, what? Just a barely noticeable facelift?
You've done the wrong pools! This Accuphase-flagship operating in Class-A
mode boasts - to stay in the picture - of its new "engine" of which the key feature is
without doubt the highly elaborate volume control circuitry dubbed AAVA (Accuphase
Analogue Vari-gain Amplifier). This is something that to this date had been reserved
exclusively for the top-of-the-line and much more expensive preamplifiers from thesame maker. Now, what's behind and how can the user take benefit of all this?
In conventional amplifiers, i.e. in the E-530 also, potentiometers are taking
care of the volume control. Evidently, by turning the knob clockwise the music
becomes louder and likewise is attenuated if the knob is turned to the left. And nomatter how elaborate a potentiometer has been constructed and built there arenevertheless inherent weaknesses by principle. To wit: impedance is always
increasing when the output level is increased which in turn is causing a higher noisefloor. And even worse: channel imbalances as well as crosstalk between channels
may spoil the listening pleasure, in particular when the potentiometer is in a position
between 8 and 9 o'clock respectively beyond 11 o'clock and therefore in ranges
below and distinctly above the average room volume level.
AAVA - the electronic trick
Fighting this root of all evil has ever since been put on top of the agenda by
the Accuphase engineers: they simply made use of the best potentiometers on themarket and consciously refrained from employing digital regulators which are (rightlyso) said to rob the sound colour and resolution.
The analogue AAVA circuitry was designed to regulate the signal from soft toloud with absolutely no losses. The input signal first meets an array of 16 parallel
voltage/current converters which are transforming the signal voltage into differently
sized "current-figures" whereby from one to the next the transformation ratio is downsized by one half. The resulting current portions can be combined in any way, yet theswitching operation is controlled by a CPU according to the position of the volume
control knob. Altogether there are 216 or 65,365 combinations possible.

At first the voltage of the input signal is via AAVA converted into a signal
current whereupon gain is set by a turn of the volume knob. Finally, the combined
current is converted back into a signal voltage. This elaborate measure is to alter
neither frequency response nor impedance and therefore has also no influence on
the noise.
That AAVA makes sense indeed could be confirmed in the many listening
sessions in which the E-550 had to mount the boxing ring versus it predecessor.
Albeit not so clearly in the classic test configuration, in which both candidates could
play with their muscles after a painstaking level-up procedure. It was in fact during
the blind test when the newcomer could slightly distinguish itself from the E-530. In
particular with symphonic music and choir (Listening Test CD-5, Audio Reference)the E-550 sounded more dynamic. Subjectively, the listening panel perceived therendition to be "louder". The E-550 succeeded in shining a stronger light onto thelowest octaves and basses seemed a tad more precise.
As far as voices were concerned we had the impression that the E-530, which
had been working hard for about four years now, was more expressive andmelodious. Yet this lead over the E-550 certainly melted down after a few weeks
when the latter began to render tenors as well as sopranos more differentiated if not
more honest. As already the blind tests (a very nice procedure, but not to be carriedout under stress) made clear, the E-550 follows the flow of the music with more innerexcitement while timing and the silence between the notes are better rendered on thepoint.
Soft and loud: brilliant
This improvement however is not only due to AAVA. A look beneath themassive lid reveals heavily modified amplification stages as well as a completely newpower supply. And the sensation of turning the volume knob from soft to loud andback was quite an experience: even at the lowest level this E-550 was simply "there".
That is, it didn't need that notorious crank up to the right to get started. And likewise
brilliantly it mastered the volume levels beyond the range of conventional
potentiometers. Eventually, the E-550 was limited only by itself: as being a pure-bredClass-A amplifier it ran out of steam sometime or other. This happened earlier whenconnected to low-efficiency speaker and later or not at all when driving speakers with
an efficiency of 90db or above.
Overall, the E-550 turned out to be superior to its rival E-530 in all issues.
Objectively, there are really no acoustic dimensions between the two, yet from asubjective point of view, this can certainly be judged in a different way.

SUMMING UP
Have you not been wondering sometimes why second-hand audio components fromAccuphase are fetching higher prices than those from the competitors? Well, that's
certainly not (only) due to their rather conservative appearance, but also due to theirsound, the service behind and the incredible reliability. So, whoever is going to invest
in an Accuphase is unlikely throwing money out of the window. I guess this message
is doing us good in these times.