darTZeel Audio NHB-108 B version User Manual
Page 25
darTZeel NHB-108 model one
User Manual, version B 1.0 Page
25
of 35
No output DC voltage drift compensation when this
function is released – please refer to the first section
of this manual – offering a truly breathtaking
sound, from whispers to loud shouts.
Only a single, small, local symmetrical DC NFB,
leading to extremely wide bandwidth, included in
the very low frequencies, without addition of any
multi polar phase shift.
The use of a very compact printed circuit board
(PCB) reduces track lengths to the strict minimum.
Reliability.
The NHB-108 model one does not use any "ex-
otic" or "esoteric" component. Each element was
chosen for its intrinsic sound qualities, its long-term
availability, and for its long life. No compromise
was conceded as to the build quality of any part or
component. Some of them were tested for 15 years
in our lab before being selected.
T5.3.2. darTZeel schematics
For the most curious readers, we give hereunder the
functional diagram of the darTZeel NHB-108 model
one
.
Connoisseurs will appreciate how simple it is, so
different from the common belief of "bigger is bet-
ter".
For once, we give the description in French, which
is, after all, the very original text. A translation can
be provided on special request.
This schematic is multi patent protected
Description du circuit:
3 étages, en technologie discrète, se décomposent
ainsi :
1
er
étage, étage d’entrée. Cet étage, dépourvu de
toute contre réaction, amplifie en courant le signal
d’entrée, de telle sorte qu’il ne subisse aucune
charge susceptible de le déformer. La simplicité
apparente de ce premier étage (1 seul transistor
par polarité) permet des vitesses de commutation
très élevées, sans rotation de phase notable dans
le spectre audio.
2
ème
étage, étage d’amplification, amplifie en ten-
sion le signal à la valeur nominale requise. Cet
étage comporte 2 demi contre réactions locales,
implantées de manière symétrique. Cette contre
réaction symétrique s’effectue sur tout le spectre
de fréquence, y compris le courant continu, afin
d’apporter une réponse parfaite dans le grave.
La configuration de ce circuit permet une propaga-
tion de groupe homogène sur tout le spectre audio,
grâce à la faible valeur de la contre réaction.
3
ème
étage, étage final de sortie, dépourvu de toute
contre réaction. Cet étage amplifie en courant le
signal issu de l’étage précédent, permettant ainsi
d’alimenter un haut parleur. Le courant de repos
des transistors de sortie est ici défini par une ten-
sion de jonction base-émetteur, et non par un cou-
rant de polarisation. Ce système élimine le besoin
d’une régulation thermique. En effet, lorsque les
valeurs initiales ont été fixées, tout échauffement
des transistors de puissance entraîne également un
échauffement des transistors drivers. La tension
VBE chute aussi bien dans les drivers que dans les
éléments de puissance, garantissant un équilibre
thermique stable. Ce montage permet également
des bandes passantes très étendues, sans dépha-
sage important.
The above description is an extract of the original
patent text, and is condensed to cover other applica-
tions, even in the non-audio field. To be added in
the fly, the darTZeel NHB-18NS preamplifier
circuit is directly derived from the NHB-108
model one
schematics.
If you have any specific questions about this circuit,
please do not hesitate to contact us at
more-
T5.3.3. Component layout
In analog, especially in audio, the layout of compo-
nents is of paramount importance in the signature
they can print onto the musical signal. A trans-
former too close to input circuits, or a power supply
located too far from output devices, are just some
examples among others. These parameters are diffi-
cult to cope with, particularly when cost considera-
tions come into the picture.
The internal volume was exploited down to the last
cubic centimetre. Output power devices are located
less than 10 centimetres from the huge crescent-like
bus bars. All the energy coming from the capacitor
reservoir can then effortlessly flow to the output
bipolar transistors.
Also, the Power Nose – please read the Owner's
manual for more about the terminology we use –
does not directly switch the AC mains, but drives
static, semiconductor relays, by mean of a dedicated
circuit powered by its own power transformer. This
approach allows freedom from any electromagnetic
disturbance from AC, and also to soft start the am-
plifier. The switch is also subject to less wear, since
no spark can appear at its contacts, extending its
lifespan close to one million ON-OFF operations.