Audio Esoterica (Australia)

Hegel
THE BACK STORY
Hegel is a Norwegian company which had a rather
strange beginning. ‘Way back in 1988, Bent Holter, a
young electrical engineering student studying at the
Technical University in Trondheim (NTNU) was paying his
way through his university degree by playing in a heavy
metal band called ‘The Hegel
Band’. As the band became
more successful and started
playing larger venues, it
needed more powerful
amplifiers, so Holter
decided to save the band
some money by building
them himself, using a new
amplifier topology based on
a circuit he’d developed for a
thesis in which he’d proved
that it was possible to
reduce distortion in an audio
amplifier without adversely affecting other performance
parameters — in particular frequency response and
damping factor. That circuit is now trademarked by Hegel
as ‘SoundEngine Technology’.
Rather than build ‘one-off’ amps, Holter decided
the circuit was so good it deserved to be built into
commercial products. Of course the new company
required a name, so Holter decided on using his band’s
name for both the name of the company and the brand
name of the amplifiers.
As for the ‘SoundEngine’ circuit itself, for which
Bent holds a patent (US6275104B1), it appears to be
a unique implementation of a technique called ‘feed-
forward’ that was first proposed and used by Harold S.
Black in 1923 when he was working at Western Electric,
after which Seidel and Beurrier worked on it for Bell
Laboratories in the late 60s, and of course none other
than John Vanderkooy and Stanley Lipshitz (University
of Waterloo) also applied themselves to improving it
in the early eighties. The version Bent patented uses
several series-connected amplifier stages with each one
having its own voltage and current gain function, as well
as its own local error correction. Distinctively, correction is
applied dynamically so that no correction at all is applied
under a threshold level, in which circumstance the gain
stages work as cascaded local feedback gain stages with
the specified voltage and current gain. Stages that are
error-corrected are able to apply different amounts of
voltage and current gain.
Bent’s patented circuit has multiple advantages,
including increased immunity to radio frequency
interference, higher tolerance to reactive speaker loads,
reduced levels of harmonic, intermodulation and transient
intermodulation distortions, stable phase across the audio
frequency range, and increased linearity at high voltage/
current levels, particularly at high frequencies.
081080
The rear panel of the Hegel H590 is nicely laid out, with high-
quality connectors used for all inputs and outputs. The layout has
obviously been thought-through, but looks a little weird if you’re
looking directly at the rear of the amplifier, because all the left-channel
inputs and outputs are on the ‘right’ side of it, and all the right-channel
inputs and outputs are to the ‘left’ side. As I said, this looks odd if you’re
looking directly at the back of the amplifier, but makes perfect sense if
you’re leaning over the amplifier from the front, because then the ‘left’
inputs and outputs are on your left, and the ‘right’ inputs and outputs
are on your right. Maybe it would have been less weird if Hegel had
gone the whole hog and printed the type on the rear panel upside
down as well as right-side up, as some other manufacturers do.
It is well worth making special note of the fact that at a time when
many manufacturers have so-called ‘balanced’ XLR inputs that are in
reality only unbalanced inputs with XLR connectors, Hegel’s balanced
inputs are not only true balanced inputs, but also use very high
precision discrete instrumentation amplifiers with high CMMR.
WEBSITE AND MANUAL
I feel the need to commend Hegel on its website, which is an object
lesson in what I think the website of a manufacturer of audio equip-
ment should look like. Each product gets its own page on which there’s
an excellent, easy-to-read description of the product’s capabilities, plus
a complete set of specifications, links to reviews, links to explanations
of the technologies used in the product, links to dealers, plus a link to a
dedicated support page that then contains links to the Owner’s Manual,
IR and IP codes, firmware upgrades, drivers and helpful guides on UPnP,
Tidal and more. There are no fancy sliders, overlays or dissolves, just a
fast, informative, and easy-to-navigate site. For example, if you’re con-
necting a computer to the Hegel H590 you won’t need a driver if you’re
using Windows 10 or Mac OS… or even Linux, but if you’re using an old
version of Windows you will need a driver, and this can be downloaded
from the support page.
And, as you’d expect from the professionalism of Hegel’s website,
the Owner’s Manual provided with the amplifier (also available online)
is also outstandingly good… very high-quality printing, well-written,
well laid out, and with useful and informative illustrations — even, on
page 9, a bit of light relief! The website and the manual certainly give
you confidence in the product.
IN USE & LISTENING SESSIONS
Your first quest will be to find the main power switch. Luckily, it’s a huge
rectangular push-button and although it’s underneath the amplifier,
Hegel has located it midway across the amplifier and very close to the
front panel, so it’s really easy to find and operate. I say this specifically
because some of the manufacturers that hide their power switches put
them in really inconvenient locations.
Once you’ve powered up the Hegel H590, the display briefly
flashes ‘Hegel’ before taking a few seconds to go through a ‘self-check’
routine that presumably makes sure you haven’t accidentally made a
misconnection. During this time, the output is muted. If the amplifier
passes the self-check it defaults to Volume 20, and the source last used.
The volume and source selection rotary controls operate almost
noiselessly, and rotate very smoothly, and both have a ‘soft’ feel that
came as a very pleasant surprise.
Hegel has designed its muting circuit correctly, so that if it’s
muted, the amplifier will automatically unmute itself and restore
normal operation if either the front panel volume
control is moved, or one or the other of volume
controls on the remote control is pressed. This is
an excellent safety feature, and prevents anyone
from turning up the volume whilst the muting
circuit is active. Hegel has also made sure that the
amplifier stays muted when you’re switching from
one source to another, which is very useful, and
very rarely implemented. Curiously, the ‘unmute’
action is not instantaneous, as I would have
expected, but it’s quick enough to be effective.
Speaking of switching from one source
to another, I did find it a bit tedious stepping
through inputs, because if you’re playing back
an analogue source via XLR1, for example, and
want to listen to a digital source via the coaxial
input, you need to press the remote IN+ button
six times. But in my experience this is only a
nuisance when I am reviewing equipment, in
which case I am switching inputs far more often
than I would normally. In real life, I tend to leave
my amplifier switched to one source or another
for very long periods of time.
The DAC inside the Hegel H590 is the AKM
AK4490, which has selectable filters of which
Hegel has implemented the minimum phase/
fast roll-off implementation. Using the digital
inputs is straight-forward — nothing required
other than to input PCM up to 32-bit/384kHz,
or DSD64/DSD128/DSD256 (via DoP). Using
Spotify is equally simple: just connect the H590
to your network, open the Spotify app on your
device (phone, tablet or laptop) using the same
local network, choose ‘Hegel H590’ from ‘Devices
Available’ and start listening. Using AirPlay is
similarly straightforward — once the H590 is
networked via the Ethernet socket on the rear,
it will automatically receive an IP address, after
which all AirPlay-compatible devices will show
the H590 in their list of ‘Speakers’. As already
noted, the Hegel H590 supports up to MQA 8×
(352.8kHz/384kHz) but only via its USB input.
Streaming music from a NAS drive, computer
or the internet requires a little more effort
because the H590 is a renderer and requires
that you download and install one of the many
free media servers that are available, such as
MinimServer, Asset uPnP, Kinsky or Twonky. I won’t
go into too much detail about this because if you
already know your way around media servers, I’d
be telling you how to suck eggs, and if you don’t,
I’d recommend you get your hi-fi dealer to install
and set up their preferred media server for you,
after which it can become your preferred media
server on whatever device you’re using.
One advantage of having its heatsinks inside
the chassis, rather than outside it, is that the
Hegel H590 comes up to its optimum operating
temperature very quickly, so there’s no need to
leave it switched on all the time; you can leave it
in its standby mode whenever you’re not using
it… saving money, and extending product life.
The Hegel H590 demonstrated its ability
to deliver enormous levels of power, and its
ability to control even the largest-coned, lowest-
impedance loudspeakers right from the outset,
while I was playing Sara Bareilles’s ‘The Blessed
Unrest’ from a few years back. Listening to Brave,
I turned the volume right up to glory in the
drumming, the bass lines and Bareilles’ sparse
piano chords. and no matter how far I went,
the Hegel H590 just responded instantly and
accurately. The abrupt conclusion to the song
made me realise how quiet the amplifier is, too;
it went from ear-shatteringly loud to total and
complete silence. It’s eerily satisfying when I hear
an amp do this… because not many can.
I admired the Hegel H590’s tonal
transparency first with Bareilles’ voice on her song
Hercules, where she demonstrates her vocal range,
and the Hegel demonstrates that no matter
where she is in it, it will reproduce it perfectly. I
followed on in track order not least to play my
favourite track on this album, Manhattan, which
THE REAR PANEL OF THE HEGEL
H590 IS NICELY LAID OUT, WITH
HIGH-QUALITY CONNECTORS USED
FOR ALL INPUTS AND OUTPUTS.
The Hegel H590
is an immensely
powerful, totally
musical amplifier
that will easily and
gracefully drive any
loudspeaker load.
HEGEL H 590 INTEGRATED NETWORK AMPLIFIERHEGEL H590 INTEGRATED NETWORK AMPLIFIER