darTZeel NHB-108 One User manual

darTZeel NHB-108 model one
Owner's Manual

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darTZeel NHB-108 model one Owner's Manual Page 3 of 17
Table of contents
1. Introduction.......................................................................................................................5
2. Brief description................................................................................................................5
3. Who am I?.........................................................................................................................7
4. Connecting and setup........................................................................................................7
4.1. Location.......................................................................................................................7
4.2. Speaker impedance......................................................................................................7
4.3. Choice of the input......................................................................................................8
4.4. Powering ON...............................................................................................................8
5. Using the darTZeel ..........................................................................................................8
5.1 Power cycle.................................................................................................................8
5.2. darTZeel's Eyes..........................................................................................................9
5.3. User parameters...........................................................................................................9
6. Maintenance....................................................................................................................10
6.1. Fuse(s) replacement...................................................................................................10
6.2. DC voltage drift.........................................................................................................12
6.3. Cleaning and upkeep.................................................................................................12
7. Some advice and tips.......................................................................................................12
7.1. What not to do...........................................................................................................12
7.2. Troubleshooting ........................................................................................................13
7.2.1. Eyes Closed................................................................................................13
7.2.2. Amplifier ON, no sound.............................................................................13
7.2.3. Warped sound.............................................................................................13
7.2.4. Sensitive fuses............................................................................................ 13
7.2.5. Sound too quiet...........................................................................................13
7.2.6. Sound too loud ...........................................................................................14
7.2.7. Blinking Eyes.............................................................................................14
7.2.8. Melting Fuse(s) at power ON.....................................................................14
7.2.9. RAS............................................................................................................15
8. Version B.........................................................................................................................15
8.1. XLR floating inputs...................................................................................................15
8.2. DC output voltage drift .............................................................................................15
8.3. Version A versus B ...................................................................................................15
9. Conditions of warranty....................................................................................................16
9.1. Breakdowns or faulty parts .......................................................................................16
9.2. Conditions of use.......................................................................................................16
10. Assistance........................................................................................................................16
11. Technical data .................................................................................................................17

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darTZeel NHB-108 model one
Owner's Manual
1. Introduction
Congratulations for purchasing a darTZeel
NHB-108 model one.
Our machines are designed and hand
built for very long lasting use and musi-
cal pleasure.
The darTZeel NHB-108 model one is a
highly unusual power amplifier, and re-
quires special care. We strongly recom-
mend you read this manual in its en-
tirety, in order not to miss any reason
for enjoying your machine at its very
best!
When opening the crate, you certainly
noticed the two separate information
sheets. They are of primary importance
and you must read them without fail be-
fore continuing.
These documents are:
-The warning notice, printed in red.
-The “3-step-to-go” commissioning
leaflet, printed in blue.
While humor is truly part of our philoso-
phy, please keep in mind that all our
warnings must be taken into account, for
the sake of your own safety.
If you carefully follow all the instructions
herein, you will be rewarded by very
long, joyful listening sessions, for years
and years to come.
Please carefully keep all documentation
and packing material in a safe place, es-
pecially the crate, in case you have to
move house one day.
2. Brief description
The darTZeel NHB-108 model one is the
pinnacle of more than 16 years of re-
search & development, with the first goal
in mind being sound reproduction, noth-
ing but sound reproduction.
Every basic element of the darTZeel NHB-
108 model one was chosen for its high in-
trinsic sound qualities. No compromise
about the cost price was even contem-
plated.
The result is what you can see, touch
and hear… right now.
One of the secrets of the darTZeel NHB-
108 model one can be found in two words:
Passion and Love… The passion for
sound, of course, and love of music,
needless to say…
As for the rest, we just put in few
electronics, a wee bit of mechanics, and
an awful lot of working hours.
If you want to know more about the
technical side of the darTZeel NHB-108
model one, we invite you to read the sup-
plied Audiophile's technical manual, in
which you should find much of interest.
Also supplied is the Music lover's man-
ual, more oriented on the sound aspects
which guided us in the making of the
NHB-108 model one. It should be taken as
the ideal complement to the Audiophile's
technical manual.

darTZeel NHB-108 model one Owner's Manual Page 6 of 17
FRONT PANEL
1. Identification Plate
2. The Eyes
3. The Power Nose
REAR PANEL
4. XLR Inputs
5. 50ΩBNC Zeel Inputs
6. RCA Inputs
7. Speakers Terminals
8. IEC Power Socket
Zi. Input Impedance Selector
4
5 5
6 6
7 7
8
ZiZi
1
3
2

darTZeel NHB-108 model one Owner's Manual Page 7 of 17
3. Who am I?
Your darTZeel NHB-108 model one bears,
on its front panel, its Identification Plate
(1). On this 24k gold plated brass plate
are engraved your name, and the serial
number. Do not unscrew the plate since
it is the identity card of your machine!
The serial number can be read as fol-
lows:
TZ-XY1081.dcbZ
X = Century of making
Y = Batch number
dcb = Identity in the batch number
Z = Version (Aor B)
Example:
The sample bearing the serial number
TZ-UA1081.001A
Is the first machine of the first batch,
made in the 21st century, and of version
A. This numbering is thus valid until the
end of the 26th century.
Unless specially requested otherwise, we
deliver all darTZeel NHB-108 in version A.
This is the version offering the most pur-
ist design, thus the best sound reproduc-
tion available.
Version B, a bit more versatile, is more
fully described in chapter 8. "Version B".
Important! The rear panel has been
designed to cater for both versions A
and B.
It is vital to bear in mind all the fol-
lowing notes and remarks concern-
ing the use of your darTZeel NHB-108
model one.
Thank you.
4. Connecting and setup
4.1. Location
Before making the first connection, you
should think carefully about the location
where you are going to put your gear. If
you planned to fit your darTZeel NHB-108
model one into furniture, please bear in
mind that you must allow at least one
inch of free space all around the unit, for
proper cooling.
If you do not respect this, the darTZeel
NHB-108 model one may stop playing if it
becomes too hot.
The heat sinks shutdown point is at
around 70°C, and the power supply
starts up again when the temperature
has dropped to 55 °C.
Please also note that permanent exces-
sive temperature will reduce the life span
of your machine. Read the Audiophile's
technical manual if you want to learn
more about this topic.
Anyway, if possible, always leave enough
space around your darTZeel NHB-108
model one, allowing you to gain easy ac-
cess to it when making connections.
4.2. Speaker impedance
The darTZeel NHB-108 model one can drive
virtually any loudspeaker, provided its
nominal impedance is between 1 and 8
ohms. Above 8 ohms, maximum avail-
able power output will be slightly re-
duced, but without any sound quality
loss.
Nominal impedance can vary by ± 20%,
and can thus reach the following critical
minimum values:
6.4Ωin the case of 8Ωspeakers
3.2Ωin the case of 4Ωspeakers
1.6Ωin the case of 2Ωspeakers
0.8Ωin the case of 1Ωspeakers
If your loudspeakers are between 4Ω
and 8Ω, which is nearly always the case,

darTZeel NHB-108 model one Owner's Manual Page 8 of 17
you can directly hook them to the Speak-
er Terminals (7).
White terminal (upper) = Ground.
Red terminal (lower) = Live signal.
If your loudspeakers impedance is less
than this, or if you want to parallel 2
pairs of 4Ωspeakers, you must go to
chapter 5.3. "User parameters" before you
consider going further.
If you do not respect the above, you
may encounter some blown fuses when
playing music at loud levels.
CAUTION: You must connect your loud-
speakers to the Speaker Terminals (7) be-
fore powering ON the darTZeel NHB-108
model one!
4.3. Choice of the input
Only one input can be used at a time. All
inputs are paralleled, so you cannot se-
lect them separately.
If you do not own a darTZeel preamplifier
yet, we suggest you use either RCA (6)
or XLR (4) inputs, with the Input Imped-
ance Selector (Zi)switched on RCA Hi Z
(lower position, physically speaking).
The XLR inputs are not balanced on the
version A:
Pin 1 = Ground
Pin 2 = Hot leg
Pin 3 = Grounded through 13kΩresistor.
If you have already paid us the honor of
purchasing a darTZeel preamplifier, we
strongly recommend using the 50ΩBNC
Zeel Inputs (5), with the Input Impedance
Selector (Zi)switched on Zeel 50Ω(upper
position, physically speaking).
The Zeel input is definitely the one that
will bring you the purest sound ever
achievable. Read the Audiophile's techni-
cal manual if you want to know more
about this topic.
4.4. Powering ON
Please do not forget that the darTZeel
NHB-108 must have loudspeakers con-
nected before you power ON.
Your machine has already been factory
set in order to adapt to your mains sup-
ply, as confirmed by the sticker on the
glass cover. In case of doubt, please
contact us.
Connect the supplied power cable into
the IEC socket (8) and plug the other end
into the mains wall outlet.
You can then power ON the darTZeel
NHB-108 model one by pushing the Power
Nose (3) button.
If a source is already connected, you
should immediately hear the music.
When powering the amplifier OFF by
pressing the Power Nose (3) button, you
can still hear the music for 10 to 30 sec-
onds before the level goes down dra-
matically and stabilizes. This behavior is
perfectly normal, and it is not a failure at
all. If you need more details about this,
please refer to the Audiophile's technical
manual.
5. Using the darTZeel
5.1 Power cycle
The darTZeel NHB-108 model one has been
designed to deliver more than 90% of its
magical sound at cold start.
After 5 minutes, you are very close to
the best the machine can offer. The in-
creasing quality you may hear as time
goes by will be mostly the reflection of
your growing musical pleasure…
No need then to leave your machine
powered ON all the time, except of
course if you like paying bigger electric-
ity bills…
If your present preamplifier produces
some clicks and/or bumps when power-
ing on/off, we suggest you observe the
following sequence:
Powering ON: first the Preamp, then the
darTZeel NHB-108 model one.
Powering OFF: first the darTZeel NHB-108
model one, then the preamplifier.
If this procedure is not respected, you
may encounter some blown fuses due to
Crowbar triggering.

darTZeel NHB-108 model one Owner's Manual Page 9 of 17
If you still hear some thumping at pow-
ering OFF, you will have to wait around
10 seconds before switching the pream-
plifier OFF. This noise, however, will be
inconsequential and harmless.
5.2. darTZeel's Eyes
The 2 giant orange LEDs, called Eyes (2)
for obvious reasons, are fully featured
function indicators. Five different illumi-
nation states, for each individual chan-
nel, are described hereunder:
1) Eyes shut (light off). This is of course
the status when the darTZeel NHB-108
model one is either powered off or not
plugged in. If one Eye only is shut, it
means that there is a power fault or
a blown fuse in the channel in ques-
tion. In the latter case, please go to
chapter 6.1."Fuse(s) replacement".
2) Idle state. 45 to 55 seconds after pow-
ering ON, and with no input signal,
the Eyes go into this barely illumi-
nated state.
3) Signal presence. When an input signal,
corresponding to over 10 mW at 8Ω
is detected, the Eyes illuminate fully.
You are in "musical cruise mode".
When the input signal disappears for
more than 45 to 55 seconds, the
Eyes go back to idle state.
4) Clipping. When approaching maximum
output power, the corresponding Eye
flashes brightly for about half a sec-
ond, and then goes back to the "mu-
sical cruise mode".
5) Blinking. If an Eye blinks, it means
that absolute DC voltage greater than
0.6 volt is present at the correspond-
ing output. This indicates that your
machine could do with some recali-
bration, though it is still working per-
fectly, musically speaking.
If absolute DC voltage continues to
grow until reaching 2 volts or more,
the Crowbar circuitry will immediately
short circuit the corresponding power
supply, protecting your precious
loudspeakers.
5.3. User parameters
The darTZeel NHB-108 model one must be
correctly set, accordingly to the loud-
speakers' nominal impedance. Your ma-
chine is already factory set for speakers
having nominal impedance from 4Ωto
8Ω, as is usually the case.
If your loudspeakers' nominal impedance
is between 1Ωand 2Ω, or if you connect
two paralleled 4Ωspeakers, you must
adapt your darTZeel to that load. If you
want to know more about this special
mode, please read the Audiophile's tech-
nical manual.
The procedure for the adaptation of the
output impedance is described here-
under:
Power the machine OFF.
!!! UNPLUG THE AC CORD FROM THE
WALL, and please wait for 5 minutes !!!
Disconnect all links you may have in-
stalled by removing all cables from in-
puts (4), (5) or (6), and from Speakers
Terminals (7). Unscrew the single central
cover screw, and remove the smoked
glass using the supplied suction grips, as
shown in fig.1 Gently wet them in order
to get firm vacuum. Please be very care-
ful when removing the cover, since it is
real glass, not Plexiglastm.
Fig.1 Suction grips

darTZeel NHB-108 model one Owner's Manual Page 10 of 17
The speaker's impedance switch is lo-
cated at the upper left of the transformer
(upper right for the right channel),
Fig.2 Speaker's impedance switch
as shown in Fig.2
When the switch is pointing towards the
front plate, you are in Lo mode, suitable
for 1Ωand 2Ωspeakers. In this mode,
you can also parallel 2 or even 3 pairs of
4Ωspeakers.
By flicking the switch towards the rear
panel direction, you set the Hi, default
mode, for 4Ωand 8Ωspeakers. This is
the most often used configuration.
The darTZeel NHB-108 model one being a
true dual mono design, you can also use
it to biamplify hybrid loudspeakers (hav-
ing different technology and impedance
drivers, i.e. an 8Ωwoofer and a 2Ω
tweeter) by switching one channel to Hi
and the other one to Lo, respectively.
Please bear in mind that in this case, you
will need two darTZeel NHB-108, one for
each loudspeaker.
Once you have chosen your configura-
tion, you can carefully put the glass
cover back, and screw it on again as fol-
lows:
Freely hand screw until you feel the
thread-end resistance. Then use the
supplied screwdriver and turn an extra
1/8 turn approximately. The screw must
be sufficiently tightened to prevent the
possibility of the glass rotating around
the screw axis.
Then reconnect all the wires and cables,
paying special attention to the loud-
speaker cables. They must be hooked to
the Speaker Terminals (7) before powering
the amplifier ON.
Now just sit back and relax, and im-
merse yourself in pure musical pleasure!
6. Maintenance
6.1. Fuse(s) replacement
The following procedure concerns the left
channel. For the right channel, the pro-
cedure is the same but that the fuse is in
a mirror image configuration.
If one – or both – fuse(s) has/have
blown, first try to determine the cause.
The Crowbar circuit installed in the
darTZeel NHB-108 model one causes fuses
to melt when an abnormal situation is
detected.
For more information about this topic,
please refer to the Audiophile's technical
manual.
If a newly replaced fuse immediately
melts when you power on your darTZeel
NHB-108 model one, even though your
speakers are correctly connected to the
Speakers Terminals (7), unplug the AC
mains and contact us directly:
[email protected]
Hereunder is the procedure:
In order to change a fuse, power off your
darTZeel NHB-108 model one by pressing
the Power Nose (3) button.
!!! UNPLUG THE AC CORD FROM MAINS,
and wait for 5 minutes !!!
Remove all the input and output connec-
tions.
Remove the single central screw located
on the top smoked glass cover. Take the
two supplied suction grips, slightly wet
them in order to provide strong vacuum,
and firmly apply them on the cover
glass, as indicated in Fig.1
Please be careful when removing the top
cover, since it is of real glass, not Plexi-
glasTM.

darTZeel NHB-108 model one Owner's Manual Page 11 of 17
Put the amplifier on a carpeted surface,
and gently (but firmly, as it is a heavy,
30kg electronic creature) pivot it verti-
cally onto its front handles. Use a protec-
tive cloth as indicated in fig.3 in order to
avoid scratching the inside aluminum
parts
Fig.3 Soft cloth
while using the supplied long nosed pli-
ers (fig. 4),
Fig.4 Supplied tools
Gently turn the fuse holder, as shown in
fig.5, 180° counter clockwise,
Fig.5
and pull it off, as shown in fig. 6
Fig. 6
Then turn again 180° counter clockwise
and let the fuse fall onto the inner side of
the front panel, as shown in fig. 7
Fig. 7
Pick up the fuse with pliers and check
that the glass envelope is dark or black,
indicating a blown fuse. Remove it and
simply install a new fuse in the holder.
Once the new fuse is inserted, push back
the fuse holder and turn it 180° clock-
wise until you feel a slight click.
You’re back in business!
Fuse ratings are:
110-125vAC: 6.3 amps slow blow.
220-240vAC: 3.15 amps slow blow.
Never use improper fuse ratings.
Very great fire risk!
Now you can restore the amplifier back
to its horizontal position and put the
glass cover on, as described in chapter
5.3. "User parameters".

darTZeel NHB-108 model one Owner's Manual Page 12 of 17
Connect again all your cables, without
omitting the loudspeakers, and power
ON your darTZeel NHB-108 model one.
Now you are ready to enjoy some more
good music, compensating all that tiring
physical effort you have just put in…
Although the above procedure could
seem rather long and complicated, you
will see that it is a simpler task to per-
form than to explain.
Anyhow, if you carefully respect all ad-
vice and warnings, you should never en-
counter such problems of blown fuse(s).
6.2. DC voltage drift
Every single darTZeel NHB-108 model one
is lovingly checked, tested and listened
to for more than 4 weeks before leaving
our workshop.
Output DC voltage drift normally does
not need any further adjustment, pro-
vided you use your amplifier in a room
temperature ranging from 59°F to 95°F
(15°C to 35°C).
If one – or both – Eyes begins to blink,
even though your loudspeakers are
properly connected, a readjustment is
recommended.
This tuning procedure is described in the
Audiophile's technical manual.
6.3. Cleaning and upkeep
The darTZeel NHB-108 model one has not
only been designed for providing you
intense moments of musical pleasure; it
is also designed to withstand the rigors
of time, especially if you take proper
care.
This is undoubtedly one of the few, if not
the only, amplifier to be virtually dust-
proof. The whole case performs heat ex-
change, while the two lateral heat sinks
regulate and maintain the correct tem-
perature. This design avoids the need for
any vent slot.
The only visible traces you will see in the
long-term will be located on the inner
side of the smoked glass, and will be due
to some natural evaporation of some
plastic packaged components.
We suggest that you remove the cover
glass once a year, and use a soft cloth to
gently wipe the glass with an appropriate
cleaning solution. Your darTZeel NHB-108
model one will then keep its "like-new"
aspect for decades, and as time goes by,
the less you will need to perform this
operation.
As for the external parts of your equip-
ment, a soft cloth or even a dust brush
will be completely adequate.
In case of fingerprints, a gentle rub with
a cloth soaked in isopropyl alcohol will be
more appropriate.
Just bear in mind, however, that the
simplest things are, more often than not,
the most efficient.
We personally found that a spot of soap
on a wet soft cloth is the best method
most of the time. Try for yourself!
As you have certainly guessed, we con-
firm that it is strongly recommended to
never use acid to clean your gear. Acid is
very corrosive and could react with the
anodized coating. Furthermore, acid is
very corrosive for the skin, too…
If you follow these few elementary rules,
you will be assured of having a very nice
looking machine for decades to come.
7. Some advice and tips
7.1. What not to do
Our advice and recommendations have
been voluntary placed close to the end of
this owner's manual. This does not mean
that they are of only minor importance -
quite the contrary.
We just thought that the following points
are not directly involved in the everyday
use of your amplifier.
However, the completely new concept of
the darTZeel NHB-108 model one calls for
certain precautions.
These few but important warnings are
the following:
1) Never, ever attempt to short circuit
the Speaker Terminals (7).
Repetitive shorts could lead to per-
manent damage to the corresponding
output stage.

darTZeel NHB-108 model one Owner's Manual Page 13 of 17
The warranty will be partially or
totally void in the event of non-
compliance with the above !
2) Do not power ON the darTZeel NHB-
108 model one when no loudspeaker is
hooked to the Speaker Terminals (7).
In such a case the internal fuses
could be blown by the Crowbar cir-
cuit.
3) Before connecting or disconnecting
the audio cables to/from the RCA (6)
or XLR (4) inputs, always flip, when
possible, the Input Impedance Selector
(Zi)onto "Zeel 50Ω" position. You will
thus avoid any of the resulting para-
sitic click and bumps.
7.2. Troubleshooting
While setting up your darTZeel NHB-108
model one, it is possible that you may not
obtain the desired results.
Hereunder we list the most frequent
problems you are likely to encounter. If
the problem cannot be solved, please do
not hesitate to contact us directly at:
[email protected]
7.2.1. Eyes Closed
The eyes are closed – I beg your pardon,
extinguished - while the Power Nose (3)
button is ON. Please check that the AC
power cord is correctly connected at both
ends, and that the mains AC voltage is
present. Just test with a table lamp. If
AC is present, it means that both pri-
mary fuses have melted. Please go to
point 6.1. "Fuse(s) replacement".
One Eye only is not lit. This means that
you have to change the corresponding
channel fuse.
7.2.2. Amplifier ON, no sound
Please check first the Eyes' illumination
state, as described in point 5.2.
"darTZeel's Eyes".
A) Idle state. No signal is present at the
input of your darTZeel NHB-108 model
one. Be sure that the source (SACD,
CD, Tuner or whatever) is correctly
selected and connected to the
preamplifier feeding your machine.
Please also verify that the Input Im-
pedance Selector (Zi)of each channel is
at the lower position (Hi Z).
B) Signal presence. The input source is
correctly connected and routed, but
the loudspeakers are not hooked to
the Speakers Terminals (7)! We remind
you that this is totally forbidden.
Okay, no trouble for this time. You are
lucky enough that the Crowbar circuit
did not melt one fuse or two…
7.2.3. Warped sound
The Input Impedance Selector (Zi)of one
or both channels is in the upper position
(Zeel 50Ω).
Your present preamplifier not being a
darTZeel (this will change one day), its
outputs cannot drive 50Ωloads.
So please switch the Input Impedance Se-
lector (Zi)in Hi Z mode (lower position).
7.2.4. Sensitive fuses
Fuses have the bad tendency to melt
much too often. Why, then, not replace
them by a higher value rating?
Please never, ever do such a thing!
Improper fuse ratings could produce a
fire! Please carefully read the Audio-
phile's technical manual in order to bet-
ter know the Crowbar circuit.
Fuses can blow if the nominal impedance
of your speakers is less than 4Ωand
your darTZeel NHB-108 model one has not
been set up to drive such a load.
Please refer to chapter 5.3. "User parame-
ters ". Then again check your fuses if you
are in doubt, by taking a look at point
6.1. "Fuse(s) replacement". Be sure that
you are using fuses of correct rating.
7.2.5. Sound too quiet
A) darTZeel's Eyes are in the following,
quasi-permanent state:
Clipping.
Your speakers are particularly ineffi-
cient! Please choose loudspeakers of
more than 84 dB/w/m …

darTZeel NHB-108 model one Owner's Manual Page 14 of 17
Alternatively, maybe your room is too
big, and that even with your old 1200
watts per channel powerhouse amp,
there was only just enough volume?
In such a situation, please do not
hesitate to consult us. We will try to
help you find a solution.
B) The volume setting of your preampli-
fier is close to maximum.
This can occur if you use either a pas-
sive or a low gain preamplifier.
The darTZeel NHB-108 model one has a
gain of 26dB, which is slightly lower –
two times – than usual. If you think
that the preamp you are using is the
preamplifier you want to die with, we
can adjust, to a large extent, the gain
of the darTZeel NHB-108 model one, for
appropriate matching.
However, this is a delicate task and
must be done by a qualified person
with a well-equipped workshop.
7.2.6. Sound too loud
Please realize that the sound of a
darTZeel NHB-108 model one can never be
too loud!
More seriously, you could find yourself
always using the volume control of your
preamplifier in the first quarter of its full
range, while getting high sound levels.
We can also decrease the gain of your
amplifier to suit your high gain preampli-
fier. Please note however, that we sug-
gest you consult us before thinking of
such a modification.
7.2.7. Blinking Eyes
A) Eyes blink at cold power ON. If your
listening room is at a temperature be-
low 65°F (18°C), this could be consid-
ered as normal, provided that this be-
havior disappears in the following 3 to
5 minutes.
In a room at a temperature above
65°F (18°C), blinking eyes indicate
that your darTZeel NHB-108 model one
could do with some tuning. However,
if this behavior ceases after 3 to 5
minutes, and especially if you can put
up with it, no adjustment is manda-
tory.
B) Eyes blink after several hours, when
the machine is hot, or even very hot
If your room temperature is above
90°F (32°C), this can be considered
as normal behavior, and normally the
eyes should stop blinking as soon as
the ambient temperature return to
"human being" levels.
Please also check that your darTZeel
NHB-108 model one is properly venti-
lated, as indicated in chapter 4.1. "Lo-
cation" and that you are not using it
at quasi-permanent power clipping
levels with 4Ωloads.
If the ambient temperature is under
90°F (32°C) but the Eyes blink, your
machine needs some tuning.
To cut a long explanation short,
darTZeel's eyes should not blink in ambi-
ent temperature ranges from 65°F to
90°F (18°C to 32°C). If they do, the am-
plifier needs some adjustment.
In all cases it is important to know the
working environment in which you will
use your darTZeel NHB-108 model one.
If you live at the South Pole or on the
Equator, a slightly different setting could
be necessary….
Furthermore, in big ambient temperature
change conditions, we strongly recom-
mend using the version Bof the darTZeel
NHB-108 model one.
If you need to know more about this
topic, can you guess what? Yes, read the
Audiophile's technical manual.
7.2.8. Melting Fuse(s) at power ON
The darTZeel NHB-108 model one features
a Crowbar inhibiting circuit working at
power ON. During the first 20 millisec-
onds, no Crowbar operation will occur,
avoiding blown fuse(s) if bumps greater
than 2 volts are detected.
However, if you power your machine ON
again, immediately after having powered
it OFF, it is possible that it will eventually
trigger the Crowbar circuit, and lead to
melted fuse(s). In such a case, you will
have to change the blown fuse(s) as de-

darTZeel NHB-108 model one Owner's Manual Page 15 of 17
scribed in chapter 6.1. "Fuse(s) replace-
ment".
In order to avoid this situation, we rec-
ommend that you wait around 3 seconds
before powering you darTZeel NHB-108
model one ON again, when switched OFF.
7.2.9. RAS (Regular And Satisfactory)
In such a situation, we sadly deplore
having no real cure.
We suggest you display your most
charming smile, relax in your armchair,
and enjoy listening to your favorite
tunes.
Symptoms should disappear by them-
selves within a few days. If everything
continues OK, please invite some friends!
8. Version B
As we told you at the beginning of this
owner's manual, the darTZeel NHB-108
model one exists in 2 different versions
The version Bhas 2 added features
compared to version A, and these are:
XLR inputs are true floating balanced,
coupled via input transformers.
Output DC voltage drift is monitored and
zeroed by an analog, low phase shift cir-
cuit.
It is always possible to swap from ver-
sion Ato version Bat some later date.
This change uses exactly the same cir-
cuits and components, as if the machine
was directly purchased in version B.
Hence a modified version becomes a
fully-fledged version B, as shown by the
identification plate (1), newly engraved.
8.1. XLR floating inputs
Having in mind the wish to satisfy every
user, we specially developed true float-
ing balanced XLR inputs. Instead of us-
ing electronic circuitry having poor com-
mon mode rejection, the darTZeel NHB-
108 model one uses very high quality
transformers.
Thus, the Input Impedance Selector (Zi)
now has 3 positions instead of 2. This
third one, located at center position, is
needed to isolate the transformers from
the audio when XLR inputs are not used.
This selection is done by means of relays
of the highest quality available. The rear
panel labeling is thus in conformity with
the version B, which is the one that will
need the most of the interventions.
8.2. DC output voltage drift
To be fully independent from external
temperature changes, a new analog, real
time correction circuit has been added.
The darTZeel NHB-108 model one is now
able to work over a great temperature
range, without any significant DC voltage
drift.
This DC output voltage drift correction
circuit can be disabled if needed.
8.3. Version A versus B
Although the version Bis more versatile
in use and significantly more expensive
than the version A, there is no subjective
sound improvement.
The use of relays, however high their
quality may be, for switching the XLR
inputs, constitutes an extra stage in the
signal path.
In addition, the circuit used for correct-
ing the DC output voltage drift, despite
all the care we put into it during its de-
sign, cannot be kept entirely outside the
signal path. This is why you can cut it
out if so desired.
It is interesting to note, however, that
when using the 50ΩBNC Zeel Inputs (6) in
conjunction with DC drift correction dis-
abled, the version Bbehaves sonically
exactly like the version A, and that the
50Ωmode is the one which offers the
highest quality available.
If you want to know more about this
topic… please read the Audiophile's tech-
nical manual!

darTZeel NHB-108 model one Owner's Manual Page 16 of 17
9. Conditions of warranty
9.1. Breakdowns or faulty parts
The darTZeel NHB-108 model one is guar-
anteed for one full year, parts and labor,
against any breakdowns or component
failure, as is the tradition in Switzerland
for such equipment.
As we see it, any warranty longer than 1
year is the obvious sign of inferior qual-
ity and design, indicating that a failure
could arise anytime.
Any component will either fail within
days or will last "forever" (several dec-
ades in practice).
This is the reason why all machines are
broken in for more than 4 weeks in con-
tinuous use, before being lovingly
packed and sent to you.
We are still fully aware that no compo-
nent is always flawless, and that a prob-
lem could arise anytime after the war-
ranty period.
In such a case, we will carefully examine
every situation, 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 darTZeel NHB-108 model
one.
9.2. Conditions of use
darTZeel and Delétraz Engineering compa-
nies disclaim any responsibility in case of
damage or injury directly or indirectly
due to any misuse, incorrect manipula-
tion, or simply the non-observance of
red warnings, and/or advice formulated
in this manual, in the Audiophile's tech-
nical manual and in the Music lover
manual.
Any non-authorized intervention on or in
the darTZeel NHB-108 model one, or any
failure due to one of the situations de-
scribed above, or any similar situation,
will render the warranty void.
10. Assistance
If you need any commercial or technical
information about the darTZeel NHB-108
model one, or if you have any difficulties
or enquiries, please feel completely free
to contact us by email at
[email protected]
or by fax at +41-(0)22784.4394.
We also invite you to visit our web site at
www.dartzeel.com
We wish you countless hours of musical
delight with your darTZeel NHB-108 model
one and do hope that you will have no
further need to read this manual except
for the pleasure…
Musically yours,
Hervé Delétraz

darTZeel NHB-108 model one Owner's Manual Page 17 of 17
:
11. Technical data
darTZeel NHB-108 model one
Nominal output power : 100 watts RMS @ 8 (Hi) and 2 (Lo) ohms.
160 watts RMS @ 4 (Hi) and 1 (Lo) ohms.
Gain : 26 dB @ 8 ohms.
Input impedances : RCA: >100 kohms, 5 Hz to 200 kHz.
BNC: 50 ±1 ohm, 1 Hz to 1 MHz.
Version A: XLR: >100 kohms bet. Pin 1 and 2 (hot leg and ground).
13 kohms bet. Pin 1 and 3 (cold leg and ground).
Version B: XLR: 33 kohms bet. Pin 1 and 2.
33 kohms bet. Pin 1 and 3.
Output impedance : < 0.33 ohms, from 20 Hz to 20 kHz (measured under 8 ohms).
Frequency response : 1 Hz to 1 MHz, +0, -6 dB (depends on measurement method).
10 Hz to 100 kHz, +0, -0.5 dB (depends on measurement method).
20 Hz to 50 kHz, ±0.5 dB (Version B, XLR inputs).
Rise time : < 0.8 µs.
Slew rate : > 88 V/µs, peak-peak.
DC voltage output Version A: < ± 590 mV max.
drift Version B : < ± 10 mV max.
Total Harmonic
Distortion (THD) : < 1 % from 7 Hz to 77 kHz
Temporal Distortion : None, at any level and load, as specified above.
Crosstalk : < 90 dB from 20Hz to 20kHz.
Signal to noise ratio : > 105 dB (A) @ nominal power.
Consumption : 150 watts @ idle, 1000 watts @ maximum output power.
Size in mm : 440 x 335 x 170 (WxDxH). Total deep with handles: 415 mm.
Net weight : 30 kg.
darTZeel NHB-108 model one amplifiers are made to last forever by
Delétraz Engineering in Geneva, Switzerland.
Delétraz Engineering www.dartzeel.com
5, chemin des Halliers
CH-1234 Vessy / Genève [email protected]
Suisse