darTZeel NHB-458 User manual

NHB-458 Monoblock Amplifier
User Manual

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Table of contents
1. Preliminary notes _______________________________________________________ 5
2. Introduction ___________________________________________________________ 5
3. Brief description________________________________________________________ 5
4. Warranty______________________________________________________________ 6
5. Installation ____________________________________________________________ 6
5.1. Unpacking_______________________________________________________________________6
5.2. Location ________________________________________________________________________7
5.3. Connections______________________________________________________________________7
6. The NHB-458 in detail___________________________________________________ 8
6.1. Front panel ______________________________________________________________________8
6.2. Rear panel _______________________________________________________________________8
6.2.1 Fuse and voltage settings__________________________________________________________9
6.3. Remote control ___________________________________________________________________9
7. Activation key procedure ________________________________________________ 10
8. User parameters _______________________________________________________ 10
8.1. Main features____________________________________________________________________10
9. How to set everything___________________________________________________ 10
9.1. Power-on sequence _______________________________________________________________11
10. Full configuration and settings ___________________________________________ 11
11. Some advice and tips ___________________________________________________ 18
11.1. Cleaning and upkeep____________________________________________________________18
11.2. What not to do_________________________________________________________________18
12. Assistance ____________________________________________________________ 18
13. Technical data ________________________________________________________ 19

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darTZeel NHB-458 monoblock amplifiers
User Manual
1. Preliminary notes
The NHB-458 cannot be user switched from a
different voltage setting than the one set at factory.
This is an operation that only your authorized dealer
can perform. Any attempt in changing voltage
setting will void the warranty.
Be sure that your AC wall voltage corresponds with
NHB-458s’ factory settings.
Your NHB-458 pair comes with a USB activation
key to provide the required identification data to
your NHB-458‘s internal CPU.
Usually, both monoblocks come already activated to
your name. If it would not be the case, you could use
the provided USB keys in order to program en
eventually unlock them. In such a case please
contact your authorized dealer.
Please refer to chapter 7, “Activation key
procedure” (page 9), for how to obtain your USB
activation-key data file.
Please read this user manual in its entirety.
As it is the darTZeel rule, we did our best to avoid
making you fall asleep. We hope to be successful in
that regard…
While already being pretty impressive out of the
box, your NHB-458 will require about 170 hours of
playing time before it approaches its full potential.
2. Introduction
Congratulations on your purchase of a darTZeel
NHB-458 monoblock pair.
The darTZeel NHB-458 is the most advanced
analogue monoblock amplifier yet designed.
Grace, Delicacy and Power are the words which
describe these musical machines the best.
The NHB-458 is the culmination, in terms of power
amplification, of more than 30 years of true love and
dedication to music reproduction.
Not only NHB-458s do joyfully distillate the
slightest “pianissimi” with unbelievable realism,
they also transport you into the heart of the musical
event, effortlessly reproducing the loudest
“fortissimo” without any kind of limitation but your
hearing threshold of pain.
Designed for uncompromising musical and
emotional performance, the NHB-458 will
nevertheless give its best when paired with the
darTZeel NHB-18NS, the only preamplifier in the
world using true 50-ohm matched impedance links
as well as the unique and ultimate analog optical
“zero contact” volume control signal path.
With its fluorescent display, you will have an easy
and comprehensive access to the various operational
menus.
With its very conservative ratings, the NHB-458 is
comparable to a never ending energy reservoir.
Bench tested at half a kilowatt under 8 ohms in
continuous mode, it can deliver twice this power
when playing music, and even much more than this
when using 4-ohm speakers.
So, please be careful when you will start to tame
these beasts. A single vinyl crackle can peaks at
more than 300-400 watts because of the
unprecedented speed and dynamics available.
Otorhinolaryngology medical consultation is not
included in the purchase price, so allow for your
hearing some time to adapt.
3. Brief description
Your NHB-458s are the result of all the research
and development we have brought to the audio
industry over the past decades.
Our passion and love for music and its reproduction
have been embodied in the NHB-458s.
The challenging goals we set for ourselves were to
design and then build a power amplifier with no
sound either built quality compromises.
You are among the very few owning a very unique
design, and we at darTZeel are very proud to share
this experience with you.
The entirely newly-developed audio circuits will
drive any real-world load in a breeze, transforming
your loudspeakers into a new window open to the
music, anyhow they previously sounded so far.
With the NHB-458s’ more than 450 watts RMS into
8 ohms, and 750 watts RMS into 4 ohms, even low-

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sensitivity speakers will put out plenty of volume
during your most demanding – dynamically
speaking – listening sessions. When it comes to
music reproduction, power is not needed in a
sustained way; then enters the phenomenal dynamic
power reserve.
Thanks to the huge 750 joules of energy available
from the enormous capacitor reservoir, short but
repetitive peaks in excess of 1 kW – yes, more than
1,000 watts – are delivered in a very clean way, and
much faster than the time of an eye blink – here we
mean a standard, human eye…
From the technical point of view, there is no doubt
that the NHB-458 is a very special machine. Every
single part was carefully selected, from the first
resistor to the last power output transistor.
Adding to the beauty, in those “green” days, we are
proud to say the NHB-458 actually runs very cool,
saving on your electrical bill.
Needless to say those extraordinary performances
deserve an equivalent outstanding dressing. We use
our own aluminum alloy, made from custom made
extrusion forms, and then both finishing and
anodizing are performed by real artwork craftsmen.
When assembly time comes, our dedicated crew
lovely assembles every module day after day until
final completion; then our assembly chief engineer
carefully looks for irreproachable making before
bringing the NHB-458 onto the final 3-days bench
test.
This is why you waited so long in getting your
darTZeel NHB-458 monoblock power amplifiers.
Not that we like to make our esteemed customers
waiting for months but simply because love is also
lot of pain and efforts to cope with, needing time to
smooth everything down.
We are indeed very proud to say that our “Never
Heard Before” motto plenty takes place when one
talks about NHB-458monoblock power amplifiers.
As for the most important thing you can ask for, and
we obviously mean the music, you will simply find
them… Enthralling.
4. Warranty
Your NHB-458s are guaranteed for one full year (parts
and labor), against any breakdown or component
failure, as is the tradition in Switzerland for such
equipment.
As we view it, any electrical component with no
moving parts either will fail within days, or will last
virtually “forever.”
This is the reason all our machines are thoroughly
tested and broken in, before being lovingly packed
and sent on to you.
We are nonetheless aware that no component is
always flawless, and that a problem could arise after
the expiration of the warranty period.
In such a case, we will carefully examine all the
circumstances, with the aim of reducing the likely
repair costs to minimum levels.
You can always trust us for customer care, as you
already trusted us when purchasing your NHB-458s.
The warranty is valid in the original country of
purchase only.
The warranty is transferable to a single second-hand
user within the first year, but only in the original
country of purchase.
5. Installation
5.1. Unpacking
Your NHB-458s are delivered in an industrial
wooden crate. We understand this is the less
appealing part of the package; however it is the only
way we found to safely ship your 70 kg/each
emotional music reproducers.
Hopefully you will not have to bother unpacking the
darTZeel NHB-458 monoblock power amplifiers;
your authorized dealer will be very happy doing this
for you, taking a chance to admire them while
installing. A separate sheet is nevertheless provided
in order to explain how to proceed, in case you
would secretly want to install your machines by
yourself, during a dark, moonless night.
Please note that in case of future shipping, the
original crate must be used if you want to avoid any
possible damage.
Do no forget securing the power supply suspension
screws before shipping. Any shipping damage will
not be covered by the warranty if blocking screws
are not installed.
The wooden crates should contain:
•Two NHB-458 monoblocks amplifiers
•Two USB keys
•Eight golden plated screws
•Eight suspension securing screws
•Two AC power cables
•This user manual

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5.2. Location
There is one “Left” and one “Right” machine.
You can check this on rear panel, looking to the
RCA input: Left amplifier has its RCA outer ring
WHITE colored, and the Right amplifier has its
RCA outer ring RED colored.
Technically there is no difference between Left and
Right machines, but as you will connect them from a
stereo preamplifier which well has left and right
outputs, why not following the rule until the end, for
once…?
Left and Right identification is also displayed when
hitting the NAME key from the front panel. But as
this function is only available when you will power
your darTZeel NHB-458 monoblock amplifiers,
knowing this when locating them may help you.
Anyway if would have reversed them, you could
always claim to your friends that you chose L and R
as if you were on the stage.
Do NOT remove blocking suspension screws until
your machines will be definitively located. Moving
the NHB-458 will induce some power supply
oscillation; in case of mechanical shock, internal
anodized parts could be damaged.
Before making any connection, you should carefully
plan the location where you will install your gear.
Best place is just next to each loudspeaker. Doing so
will help to minimize speaker cable length; when
connecting your NHB-458s to a darTZeel NHB-18NS
preamplifier, we strongly recommend using our
darT to Zeel 50-ohm links which will not only
allow for ultimate performance level but also having
the preamplifier – and the rest of the installation –
located as far as needed, without any sound quality
loss.
We do NOT recommend installing the NHB-458s in
any furniture, unless you are healthy enough to play
with 70 kg at arm’s length.
Therefore, please be forewarned that the NHB-458
will stop playing if it becomes too hot. This is not a
situation which should ever occur under normal
listening operation, though.
Thermal protection will shut down your NHB-458s
at approximately 70°C (158°F). The power supply
will start up again when the operating temperature
will have dropped to 60°C (140°F).
It is also advisable, where possible, to leave enough
space around your NHB-458 to allow easy access
when making or changing connections.
5.3. Connections
Be sure that your AC wall voltage corresponds with
NHB-458s’ factory settings.
CAUTION!
Never, ever proceed to ANY connection /
disconnection before NHB-458s have been
powered off by at least 2 minutes!
Internal capacitor bank stores a lot of energy, and
any wrong manipulation and / or short could
possibly lead in a catastrophic failure by avalanche
breakdown.
Be sure that there is no short between speaker wires!
Warranty will be void if the above is not respected.
As internal supplies are ± 100 volts DC, we anyway
strongly recommend not playing with the rear panel
when the machine is ON. Those are lethal voltages,
so better not risking a shock – even if non-lethal in
most of cases – by playing with wires when the
NHB-458s are not switched OFF.
Apart from these – we hope so – scaring enough
indications, we want to reassure you in the way that
once your amplifiers will be properly connected, you
will have ones of the safest machines ever designed
in front of you.
Take your time when making all connections, check
them twice if needed. Here again, we think that
asking your authorized dealer for proceeding will be
a good idea.
Speaker binding posts are from CardasTM . We chose
this kind of binding posts because they allow for
very big spades, greatly help in avoiding – most of
cases – unwanted shorts, and they are the only ones
which can be well tightened up without being lose
over time. Thank you CardasTM!
When properly tightened, these connectors are
pretty reliable and well keep the pressure on spades.
Never use pliers to tighten, only do it by hand, the
provided external rubber is very helpful to just
tighten as firmly as needed without going mad.
In the case you would prefer banana plugs – which
also have our favor – ask your authorized dealer for
supplying a Spade-to-Banana adapter. We did not
chose 5-way/Banana binding posts for the NHB-458
because of quite high current and voltage involved.
As soon as the NHB-458 is plugged into the AC
wall outlet, its operation-status LED will turn red.
There is no master hardware (physical) on/off
switch. We hope you nevertheless will sleep well,
knowing that the NHB-458’s electrical-power
consumption in standby mode is less than 5 watts for
the pair.

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6. The NHB-458 in detail
6.1. Front panel
Hereunder functions are for direct keying.
Full key operational functions using the Menu Control
Panel are described in chapter 10.
1. Power Switch
When powered OFF (Stand By):
LStatus Led is RED.
When powered ON:
LStatus Led is AMBER.
2. Menu Key
This key gives access to all user parameters
described later in chapter 10
3. Upper Display Reading
When depressed twice and more, upper reading will
change from RMS, Peak, PeakHOLD, etc.
4. Lower Display Reading
When depressed twice and more, upper reading will
change from RMS, Peak, PeakHOLD, etc.
5. Name
When depressed twice, owner name with serial
number is displayed for about 10 seconds; another
hit will display the owner name continuously.
Depressing once again will display the darTZeel
logo continuously. A last pressing and the display
will resume to standard readings.
6. Display Illumination
When hit twice, AUTO DIM will be activated, meaning that after a predefined time, the display will shut off.
Depressing twice again and the AUTO DIM will be disabled.
The defined time after the display shuts off can be set via the Menu Control Panel; see chapter 10.
7. Menu Related Key
This key has no operational function when hit but only activates the direct key access display, as it is the case
for all other 3 to 6 keys.

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6.2. Rear panel
We think the rear panel labeling speaks for itself.
Nevertheless, we will try to keep you awake, by providing
some general information… .
Please note that only one input can be used at the
same time. All inputs are connected in parallel, so
connecting more than one input at a time will
dramatically reduce sound performance.
As you will see, 2 “Power on triggers” are provided.
They are intended for remotely power the amplifiers
ON when using a darTZeel NHB-18NS preamplifier.
These triggers are NOT standard 3.5mm audio jacks,
but signal oriented, professional Neutrik sockets.
Please ask your dealer if you want to use this feature.
As mentioned earlier, your darTZeel NHB-458
monoblocks amplifiers should already be programmed
for you, and activation would not be needed; Anyway,
you will note that we provide one USB port on the
lower left corner. This is the one into which you will
insert your USB key if further registering will be
required, or when a firmware update becomes available.
For whatever reason, if your machines would not have
been factory activated, please immediately ask your
dealer in order to obtain your registration key.
When you register your NHB-458, you will need to
insert your USB key into the rear panel’s USB port.
Please carefully read the chapter 7, “Activation key
procedure”, next page.
!!! YOUR MACHINE WILL OPERATE
FOR ONLY 15 MINUTES IF NOT PROPERLY
ACTIVATED !!!
6.2.1 Fuse and voltage settings
The voltage of your NHB-458s has been factory set.
Be sure that your AC wall voltage corresponds with
NHB-458s’ factory settings.
From 100 to 125 volts AC, the rear breaker is
indicated 16A.
From 200 to 250 volts AC, the rear breaker is
indicated 8A.
There is no any fuse to replace. The thermal breaker
is only intended to protect the machine and your
installation against catastrophic failure. No Fuse,
Better Sound!
Operating voltage cannot be user altered for
technical and obvious safety reasons – remember the
± 100 volts DC internal supplies and the huge
energy provided by the capacitor bank. No any
“switch” could handle those high current/voltage.
So, if you move to another country, you may have to
change the voltage setting. Please contact your dealer.
In this case, a new activation code will be required.
!!! Warning !!!
Any attempt to alter voltage setting will void the
warranty. Always ask your dealer for such an
eventual change.

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7. Activation key procedure
In case your darTZeel NHB-458 monoblock
amplifiers would not have been factory activated,
they will operate only for the 15 minutes following
each new powering on.
Please contact your dealer for remediate to this very
deploring situation in order to quickly activate your
machines.
Registration procedure:
We provide a USB activation key with each of your
NHB-458s. This keys are blank when you receive
them.
Ask your dealer to send you your activation-key data
files.
Please note that you will need both a “Left” and a
“Right” activation keys. You can know if which
machine is “Left” or “Right” by depressing the
“Name” key from the front panel, The serial number
ends either with an “L” or a “R”. Activation keys are
not interchangeable from Left to Right.
You will receive those by email in the form of a
zipped (data-compressed) folder containing a file
with a “dtz” name extension. If possible, use a PC
WindowsTM based computer when unzipping the
files; sometimes MACTM based computers could
corrupt the files and activation will not work.
How to proceed:
1. Unzip (decompress) the key-activation
software from the zip folder. Directly copy
the “dtz” file onto the USB key, using your
home computer. DO NOT ALTER THE
FILE NAME!
2. Insert the “loaded” USB key into the USB
port located in the rear panel of your
NHB-458.
3. From the front panel, sequentially press the
following: Menu ► Diag ► DTZ.
4. The file will be uploaded.
5. Remove the USB key.
At registration-inquiry time, please note that your
owner name cannot exceed 14 characters
maximum in length. So, please use “J.D. Smith”
instead of “Jonathan Donald Smith”… .
8. User parameters
The section starting at chapter 10 is the most
important part of this user manual.
Thanks to the intuitive menus, you will be able to
access all parameters directly from the front panel.
8.1. Main features
From the Menu Control Panel, you can, from other
things, adjust the following:
•Input ► RCA OR ZEEL OR XLR. Factory
setting is ZEEL. Remember you cannot
connect multiple inputs at the same time.
•Output gain ► 26dB or 32dB. Factory
setting is 32 dB.
•Power ON mode ► Music, Trigger, or
Manual (trigger OFF)
•Display intensity ► 25%, 50%, 75% or
100%. Factory setting is 25%. Please note
that using 100% all the time will reduce the
display span life.
9. How to set everything
The following pages show how to fully set up your
NHB-458s, by mean of schematic flow charts.
We reproduce most of display screens and explain
how to proceed, as if you were in front of your
machine.
Important note
In all Menu levels, depressing the “OK” key will
confirm the level you are in, and then you will be
able to alter settings. When not pressing “OK” first,
using arrows will make you navigate into another
Menu at same folder level.
Maybe trivial for your skill but nevertheless useful
to know… See chapter 10 for full explanations.