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ES9018
based DAC
is the third edition design:
A lot of customers recommended ES9018 to me one year ago, during
this year I made a lot of practice, at Jul. 2009, I finished the
first edition and spend lot months to test and audition. At Mar.
2010 , The second edition finished. The regular edition finished at
Jul. 2010.
Click image to enlarge.
About ACSS:
ACSS (Audio-gd Current
Signal System) is Audio-gd's system for transmitting audio signals in
the current domain. This concept, first seen in 1966, we have used for
many years, and since 2006, have evolved the technology to include all
audio signals in our systems from the digital source to the power
amplifier. Since 2005, ACSS comp5nts have become Audio-gd's most popular
products.
About NFB?
NFB means Non-Feedback.
The NFB-10ES applies the
newest ESS high-end Sabre32 DA chip ES9018 which can support up to
32Bit/96KHz input . Similar to other ES9018 designs, Our NFB-10ES applies
Non-feedback ACSS output stage. The ES9018 feed to the ACSS output
stage without any OPAs so it can achieve very neutral sound quality.
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
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.
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 DAC is without couple
caps to avoid coloration.
Real fully balanced discrete
design.
Fully
Discrete ACSS headphone amp.
Click image to enlarge.
 
NFB-10ES applies the excellent DA chip ES9018 and excellent analog
output stages, 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-10ES
uses 7 groups of high-quality PSU
with dedicated DC
supply. Digital and analog voltages each have separately isolated
internal power regulations.
The
analog power supply is more important for sound reproduce, in NFB-10ES,
the +15V and -15V for the ACSS analog output stages are high speed
Discrete PSU. They can offer pure and quick power supply for driving
the headphone exactly. The high voltage power supply can drive most
headphone from 15 to 600 ohms as well.
Strong power supply.
Click image to enlarge.
About volume in ACSS circuits:
For a headphone amp, the
volume control is very important.
NFB-10ES use ACSS technology, which is very
different from conventional technology. In conventional technology the gain is fixed, like 3DB or 6DB.
But in ACSS
technology the gain changes with volume, and when you turn off the
volume, the gain is -80DB or -100DB (in conventional technology it
can't work lower than 0DB).
While you are listening in normal
volume, the gain may be around -50DB, or between -80 to +12DB.
The volume control is also
different from conventional technology. Conventional technology volume
control is placed in the input, and attenuates the signal.
But in ACSS, it is placed at the
ACSS modules 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 D/A
chips output I/V conversion)
As you can see, ACSS circuits have no
gain, as it is a completely different circuit.
The sound quality benefits from I/V
conversion volume control. 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 through the R-2R network to control the
volume, and then change back to voltage signal (V) again. But NFB-10ES is simply a more complete work in terms of the current signal,
and technically, it is superior to conventional technology.
About the A-D type relays based volume
control:
In NFB-10ES is
applied an exact A-D (analog to digital) type relays based volume
control. It has a built-in CPU to pick up the analog volume pot
position, through a ADC change to digital signal for the CPU count
and control two relays volume boards through changing the DALE
resistors to control the volume.
This A-D type relay-based
volume control has 32 steps, and with the High/Low gain switch is just
like a 64-stepe, wide-range volume pot which can suit most users
requests.
This A-D type relay-based
volume control can avoid channel imbalance and sound better than normal
volume pots.
For long long life, we apply a ALPS
27 volume as the analog position volume pot.
ALPS 27 analog position volume pot
Exact volume control
board
Click image to enlarge.
DALE resistors & WIMA caps Neutrik socket
Click image to enlarge.
The
NFB-10ES Functions:
Front
plate:
Power switch: Power ON/OFF
the NFB-10ES.
Balance Headphones socket: Output for balance headphones.
Gain switch: Select
gain between low gain (+0DB) and high gain
(+12DB).
Volume knob: Control
the volume level of the headphone and variable DAC output.
1/4' headphone socket : For single-ended headphones.
Preamp button: Select the NFB-10ES output between
dedicated DAC output or headphone
output ,the dedicated DAC output level can be chosen
between variable and fixed .
Selector switch: Select
source between BNC, coaxial and optical.
Rear:
BNC socket: For BNC coaxial input.
Opt socket: For optical input.
Coax socket: For coaxial input.
Gain switch: Select
gain between low gain (+0DB) and high gain
(+12DB).
Line out sockets: For dedicated DAC output. (The DAC output level can
be chosen between variable and fixed , see below).
How to set the NFB-10ES DAC output
as variable line level only?
The
NFB-10ES has dedicated DAC output for RCA ,XLR and ACSS. In default its
output level setting is at fixed. But owners can set
it to output variable line level (if your amp or active speakers
don't have volume control, we advise setting to variable output only).
See the photos, pull off the jumper to
set the DAC output to variable only.
Please note, the ACSS output is only available
at fixed level mode.
Setting the Fixed and variable
output
If we only use the RCA or 1/4' headphone output, is the NFB-10ES wasted or not
fully utilized?
The NFB-10ES is a real balanced output DAC and headphone amp, it has balanced (ACSS,
XLR and balanced headphone output), single-ended output (RCA and 1/4'
headphone output). There are 4 ACSS modules in the NFB-10ES
for balanced output, and all the ACSS modules have balanced input, so
even through single-ended output,
the ES9018 chips will perform fully.
Choice of
power cable appropriate for your country:
When you place the order
for NFB-10ES, please let us know the type of power cable you require.
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