Audio-gd products had
design and test based on the AP SYS-2722 (The top-drawer
professional equipment in world)
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 NFB-1AMP:
The C-2 is a single ended head amp and preamp (+/- 30V DC high
voltage power supply ), The NFB-1AMP is balanced head amp and
preamp (+/-15V DC power supply ). So They have same output power
specs that can drive most headphone very well.
If customer has headphones with
single ended connector (6.3MM), choice would be C-2 you will get
better performance than the NFB-1AMP.
If customer has the balance
connector headphone or can modify the headphone with balanced
connector, choice would the NFB-1AMP.
Class A design
built by discrete analog stages without any OPA or coupling caps
in the signal channels.
Non- feedback ACSS and output
stage designs just same as our top grade Master 9
Total applied 4 pcs exact matched 150W transistors in pure class
A output stage.
3000MW at 25 ohm Pure Class A
,drives most headphones working in pure class A , 8000mW at 40
ohm max output, no matter if you have low sensitivity headphones
+/- 35V DC high voltage power
supply built in, Class A PSU's for DC supply.
Uses most Hi-end grade parts
and exactly matched transistors, OCC wires.
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 sensitivity
headphones and speakers
10 DB and 19DB gain can drive the
high and low sensitivity headphones
5 groups input: RCA X4, ACSS X1
Preamp output : RCA / RCA / ACSS
Headphone amp output: 4pins XLR
X1 / 6.3MM X1
Detail of the Current Conveyor (ACSS) Technology
There are a lot different quality DACs. They had different design
and output impedance . To avoid negative effect on sound quality by
differences in DAC's output impedance, in the C-2, we have design a
pair single-ended class A FET buffers in the input . All the RCA
input signals go through these FET buffers, the output impedance
become very low, even if the source have high or low output
The FET buffers working in pure
class A , and it has a short signal journey. this way we can keep
the sound quality without colouration ,(dry and harsh) .
has 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 . The simplest and shortest signal journey brings
out the most neutral and least coloured 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 ears. Here it is a conflict of the
But the ACSS opens a new
field, it can offer a least colouration 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 pure
class A mode.
The C-2 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:
C-2 have in its design a pare diamond differential output stages,
every parts has been exactly matched before assemble so don't need
any adjustment .
The output stages have
two pairs of 150W transistors offer 3000MW at 25 ohm Class A ,drive
most headphones (work in pure class A ) 8000mW at 40 ohm max output,
no matter if you have low sensitivity headphones
The 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 linearity , so it provides a
very clean power supply.
The C-2 applies separate
linear PSUs for the display and control parts, to avoid the noise
through power line from affecting the amplifier.
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 sound stage distortion .
Even the high performance volume pot can still cause the loss of
details . Whatever quality volume pots, S/N will be adversely
But in the
C-2 , 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 as current signal and not
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 loose any detail. It want
degrade sound quality at any 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 C-2 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 more neutral sound .
In C-2 we applied a digital control relays based volume control.
.C-2 has total of two channels going through the DALE resistors
to control the volume to avoid channels imbalanced .This
achieves the best performance and sound quality.
C-2 have 100 steps volume
control, very smooth control for both high / low sensitivity
headphone and speakers. While users change the volume, the
combine relays break or close, it may have slight switch sound
on output but will disappear when you stop changing volume.
C-2 Supper two sets Exponential volume characteristic
design has no compromises , it's built fully with aluminium ,
the transformer interference can't travel through the aluminium
chassis and be transferred to the analog amps, and there are two
shielded boards to insulate the transformer and the power
Uses all Hi-end grade components, including DALE resistors, WIMA caps,
custom order NOVER (UK brand) caps.