Audio-gd products had
design and test based on the AP SYS-2722 (The top-drawer
professional equipment in world)
Since 4th. April
2018, the model had upgrade the volume ports:
volume ports had built with Vishay or KOA resistors with dual
resistors parallel , tolerance low to 0.05% .
Different to the C-2 ( 11th Anniversary Edition ):
The C-2 is
a single ended headamp and preamp (+/- 30V DC high voltage
power supply ), The NFB-1AMP is balance headamp and preamp
(+/-15V DC power supply ). So They had same output power specs
can drive most headphone as well.
If customer like to keep your headphone with single ended
connector (6.3MM), choice the C-2 get better performance than
If customer had the balance connector headphone or can modify
the headphone with balance connector, choice the NFB-1AMP.
Fully balanced class A design built by discrete analog stages without any OPA or coupling caps in the signal channels.
Non- feedback ACSS analog output stage.
8000mW at 40 ohm output, 16DB gain can drive the low sensitivity headphone very well.
Class A PSU's for DC supply.
Uses most Hi-end grade parts and exactly matched transistors, OCC
Four-channel 100 steps digitally controlled relay-based volume
control avoids channel imbalance and improves sound quality .
Supper Exponential Volume Characteristic, easy match the
volume with very high headphone / speaker without change the
5 groups input:
RCA X2, XLR X2, ACSS X1
Preamp output :
XLR / RCA / ACSS
Headphone amp output: 4pins XLR
Static storage mode control software for avoid disturb sound
quality , the MCU output once control data and save in the
perform parts ,then stop output data until users next operation.
Detail of the Current Conveyor (ACSS) Technology
There are a lot different DACs in worth, they had different design
and output impedance . For avoid the sound quality effect by
different DAC's output impedance, in the NFB-1AMP, it had design two pair
single-ended class A FET buffers in the input . All the input
signals through these FET buffers, the output impedance had become
very low, even the source had high or low output impedance.
buffers working on pure class A state, and it is so short signal
journey , it can keep the sound quality without coloration ,dry and
NFB-1AMP had the same ACSS design with our top grade model Master 9 . It
is a pure class A design built by discrete analog stages without any OPA or coupling caps in the signal channels.
They seem complex , but in fact they are the most simple design
the world has ever had , their a lot components to process the power
supply. The simplest and shortest signal journey brings out the
most neutral and least colored sound.
The ACSS is a non-feedback
technology made with 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.
All signal gain is in current
area, all transistors
work in class A mode.
The NFB-1AMP has all components
exactly matched before installation.
Super low THD ¡]Test by AP
SYS-2722,0DBV output level) Flat
frequency response ¡]Test by AP SYS-2722)
Strong class A output stages:
The NFB-1AMP had design a pare diamond difference output stages, every
parts had exact matching before assemble so don't need any human
output stages had four pair 15W transistors ,they also working
under class A state . Drive most headphones can working
under pure class A state.
class A parallel connection PSU has very high input impedance to avoid
pulse through the PSU from affecting the preamp and low
output impedance with very fast speed and high linear, so it is a very
The NFB-1AMP applies seperate linear PSUs for the
display and control parts, avoid the disturbances through power line
from affecting the amplifier.
combine relays break or
close, it may had slightly switch sound on output and disappear
while stop change the volume.
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 .
the NFB-1AMP , 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
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-1AMP 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 .
is applied a digital control relays based volume
control. .NFB-1AMP 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
NFB-1AMP have 100
steps volume control, very smooth
control for both high / low sensitivity
headphone and speakers.
While users change the volume, the
NFB-1AMP Supper two sets Exponential volume characteristic
Static storage mode control software:
In most control softwares design,
the MCU will continuously output data to the perform parts , the
MCU had the very high speed, so the output data become high
frequency impulses disturb the audio signal circuits make the
sound worst .
had applied static storage mode
control software , the MCU output once control data and
save in the perform parts while just power on and users operate
,then stop output data until users next operation. This design
make the sound quality improve on the clear and transparency .
The NFB-1AMP design had not compromise , it's built by full aluminum
chassis, the transformer interference can't through the aluminum
chassis transfer to the analog amps, and there are two shield
boards for insulate the transformer and the power supplies.
Uses all Hi-end
components, including DALE resistors, WIMA caps, custom
order NOVER (UK brand) caps.