darTZeel NHB-18NS mk2 preamplifier with built-in phono stage


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The darTZeel NHB-18NS is the logical partner to the now acclaimed NHB-108 model one power amplifier.
In keeping with the very same philosophy, darTZeel uses dedicated circuits reduced to their most basic form. Here again, there is no application of any overall negative feedback. The delicate, small audio signal amplified by the NHB-18NS only passes through 8 silicon junctions from input to output, including the 13dB full discrete gain stage. For the phono stage, we only add 3 junctions, for a maximum additional boost of 60 dB (73 dB in total).
The advantages of these new circuits, whose designs are patent pending, are in the same league as the NHB-108 power amplifier: an extreme, pure sound quality never achieved before.
Leading-edge audio electronics
At this level of performance, every detail is of prime importance.
The delicate, small signal delivered by the sources is amplified by discrete devices, or by means of matched transistors embedded in dedi-cated integrated circuits.No operational amplifier is used in the entire signal path. As for the NHB-108, all components used in the NHB-18NS preamplifier, with no exception whatsoever, are based on the finest products being produced by leading-edge industries at the present moment.
The first aim of the NHB-18NS is to provide sound reproduction quality Never Heard Before.
Instead of offering a preamplifier based on the same approach as that of our competitors, we at darTZeel chose to think differently, offering for the first time in the world what previously seemed impossible:
    * No contact or switches or relay of any kind for the selection of the sources. This revolutionary feature brings a new level of transparency. Instead of routing the signal through a selector box, each input has its own dedicated gain stage, which is enabled or disabled according to the user’s choice. The signal is then directly routed to the volume control module.
    * A whole new volume control module, which completely avoids the use of any potentiometer, stepped attenuator or analog switch array in the signal path. The sound signal is attenuated in a fully passive way, within a continuous range of close to 90 dB, in full analog mode, without the use of any VCA or other active component.
Both of these breakthroughs constitute a big step in the right direction: no harm to the signal. As mentioned above, this new design is patent pending. As soon as the patents are confirmed, darTZeel will be pleased to describe in detail how such signal treatment is possible.
The NHB-18NS is not only new in these aspects. We have also included all the features already implemented in our now famous NHB-108 model one, as follows:
    * Only small local negative feedback at the inputs.
    * One small, symmetrical, local negative feedback in the voltage gain stages.
    * Open loop, free of all negative feedback for the output stages.
In addition, the NHB-18NS features full modular possibilities, including future use of multi-amping by using darT to Zeel 50-ohm links. Some key features are (per channel):
    * 6 inputs, whether phono, RCA/BNC or balanced XLR. As standard, the NHB-18NS is delivered with 1 phono MM/MC input,1 full floating XLR input and 4 RCA/BNC 50 ohm Zeel inputs.
    * 1 XLR full floating output.
    * 3 BNC 50 ohm darT outputs, ready for tri-amping, with optional built-in passive filters.
    * 1 RCA output.
    * 1 RCA record output (fixed level).
Power supply
The darTZeel NHB-18NS is an authentic dual mono preamplifier, from input to output, with separate grounds for left and right channels.
Each channel is battery powered by its own battery bank, offering 10 to 12 hours of listening pleasure before a charge is needed.
A very sophisticated, regulated and dedicated supply for every input and output is provided, ensuring the lowest power supply impedance possible.
A smart automatic function is provided as standard, allowing full battery operation when listening, and charging mode being activated when the preamp is switched off. Hum is gone forever, and there is no need to worry about knowing if batteries need to be charged or not.
Technical Specification
Output voltage:              4 volts RMS for RCA and XLR outputs, 2 volts RMS@ 50 ohms (darT outputs)
Input impedance:           Line RCA > 30 kohms, from 5 Hz to 200 kHz
                                       Line XLR  > 15 kohms, from 20Hz to 40 kHz
                                       BNC 50 ± 1 ohms
Output impedance:         50 ohms for BNC, < 100 ohms for RCA, 600 ohms for XLR
Bandwidth:                    10 Hz to 100 kHz, +0, -0.5 dB.   1 Hz to 1 MHz, +0, -6 dB (XLR: 20 Hz-20 kHz ± 0.5 dB)
Rise time:                       < 0.8 µs
THD:                               < 1% from 7 Hz to 77 kHz
Temporal distortion:      None
Signal to Noise ratio:     Line > 90 dB (A) @ 2 volts RMS output.
                                      Phono MM: > 85 dB (A) @ 37 dB gain.  MC: > 70 dB (A) @ 60 dB gain.     
Power consumption:     7-70 watts depending on operating mode
Dimensions:                  18 (W) x 7 (H) x 14 (D) inches
Weight:                         58 lbs. total (preamplifier 51 lbs., power supply 7 lbs.