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ACSS:
The
NFB-20 applied real balanced fully
discrete amp without any OPAs (the OPAs in NFB-20 only for DC
serve) ,without any couple caps ,fully non- feedback . Applies the 2 Pieces high-end grade
WM8741 which can support up to
24Bit/192KHz input . Compare to other WM8741 designs , we applied Non-feedback ACSS
analog stages. The 2 pcs WM8741 feed to the ACSS analog
stages without any OPAs and couple caps so it can avoid sound coloration .
The ACSS is a non-feedback
technology made with fully discrete amplifiers. Most people know the
global
feedback design can offer better specs in test measurements, and
classic non-feedback can't do well in test measurements but can offer better
sound for the human's ears. Here is a conflict of the classic circuits.
But the ACSS opens a new field, it can offer a least coloration sound
which is more neutral with very low distortion and high linearity. So
it can retain the dynamics, detail and neutral sound but not sound
bright or harsh.
Output buffer:
The output buffers are Non-feedback. For low impedance, we
applied a diamond output stage which is quite less colored than most
conventional circuits.
The analog part is without couple caps to avoid coloration, and
power supply by four groups class A PSUs.
Applies ACSS technology, even though maybe you only connect to XLR
or RCA output, NFB-20 will always operate in ACSS technology,
and benefit from ACSS technology. Therefore, XLR and RCA output will
also definitely bring about improvement in sound quality. Even
through RCA output, the 2pcs WM8741 DA chips will perform fully.
Power supply:
NFB-20 applies the excellent
2 pcs
WM8741 with
excellent analog
output amps, but these are not the only keys of the best sound.
The power supply is most important. Even applying the best DA chip
and the best amp, if matched to a normal power supply, the total
sound may still be average or sound musical, but can't be neutral
and detailed. That is why it is easy to find hi-end grade gears
maybe without the best chips or amp stages, but with plenteous
dedicated DC supply circuits.
The
NFB-20 uses
11 groups of high-quality class A parallel
connection PSU , which can
offer very clear DC power for the DAC and amps,
producing
a very black background and neutral sound characteristic. The
class A PSU is very important for digital parts. Some designs
may have very low jitter in theory, but if the power is supplied by
a dirty or low-speed power supply, it will increase the jitter and
pollute the data, and degrade the sound quality obviously.
The class A parallel connection PSU has very high input
impedance to avoid pulse through the PSU from affecting the DAC and
low output impedance with very fast speed and high linearity, so it
is a very clean power supply. In my experience, its sound is better
than battery power supply, better human sound and neutral.
The NFB-20 uses three high performance transformers. More than
50,000uf audio grade NOVER capacitors are used to ensure ample and
smooth power feed. A total of 11 groups class A SPUs and 2 groups
linear PSUs are used to purify the power supply. To achieve high
S/N, the control circuit is powered with separate regulator.
Volume
control:
In
NFB-20
is applied a four channels digital control relays based volume
control to avoid channel imbalance and improve on sound quality .
The NFB-20 has 99 steps volume control rang allow users smooth
to control the volume level .
The volume control is also different from conventional
technology. Conventional volume control technology is
the volume control implement in the analog amp
input stage through a volume pot to reduce the signal . The
volume pots quality effect the sound quality direct , the low
quality volume pot cause lost the detail and channels imbalance
cause the soundstage distortion . Even the high
performance volume pot still cause the detail lose. Whatever
quality volume pots, must cause the S/N worst .
But in
the NFB-20 , we applied the I/V conversion volume control ,
the volume control just a
variable passive I/V conversion place at the ACSS amp output ,
where the output is the current signal, not the voltage signal. The
volume control is I/V conversion, and the volume depends on the
current (I) conversion to the voltage (V). (Like R-2R D/A chips
output passive I/V conversion)
It can keep the signal frequency band flat and
not lost any detail.
It can't degrade on sound
quality in every volume level . After the volume , there are four
groups
diamond non-feedback buffer output stages offer the
very low output impedance .
Mark Levinson also knows that current volume control has great
benefits, so in their Top End preamp NO.32 volume control, they use
many components to change the signal to current signal (I), then
implement the volume control
, and then change back
to voltage signal (V) again. But NFB-20 is simply a more complete
work in terms of the current signal, and technically, it is superior
to conventional technology.
The less conversion bring much neutral sound .
The volume
control quality is much important in the real balance gear . It must guarantee the
four channels signal control exact to achieve the performance of the
real balance gear . If the cool and hot of the balance signal
can't guarantee exact, the balance output will has large distortion
cause the sound quality and performance even much worst than a
single end gear waste the balance gear design and the cost.
In
NFB-20
is applied a four channels digital control relays based volume
control. .NFB-20 has total four channels through changing the
DALE resistors to control the volume for avoid channels
imbalanced ,achieve the best performance and sound quality of
the gear.
NFB-20 allow
users select between 99 steps exponential characteristic volume
control and 70 steps linear characteristic volume control,
whatever volume control allow users smooth to control the volume
level .
The
NFB-20 has memory of all control data even power off .
Shield:
NFB-20 has complete separation of left, right
amplifier channels, power supply, and transformer.
NFB-20 uses heavyweight all-aluminum alloy chassis to prevent the
eddy current of transformers from interfering on circuit board.
NFB-20 applies optical couple isolation for the MCU and the
control implementations to prevent the MCU affecting the audio parts.
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Summarize
