Detail of the Current Conveyor
and short signal path
The D-28 applies the newest ESS high-end Sabre32 D/Achip
. ES9038Pro can support up to 32Bit/768KHz input .
The ACSS circuit naturally works in current mode , it can
transfer the ES9038Pro current signal to the output and
implement the I/V conversion in current mode in one ACSS amp .
And this ACSS amp only have one current gain stage , the
ES9038Pro output signal only go through one stage which is very
short signal path .
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 quality .Here is a
conflict of the classic circuits.
But the ACSS design opens a new field, it can offer a least
coloration to the sound which is more neutral with very low
distortion and high linearity. So it can retain the dynamics, detail
and neutral without being bright or harsh.
The D-28 has 4 groups of
Zero distortion diamond rhombus output
stage for the balance output . Every part has been
tactfully design , can achieve zero distortion
state without any adjust .
The output stages have built
in 4 pairs of 15W transistors to offer strong drive capability
The D-28 has the large pure
class A output power (1500mW at 100 ohm, max 9500mW at 25 ohm) , drive most headphones
to listen music not to exceed the pure
class A area.
The balance drive mode kills the noise and
distortion ,improves the sound stage, background and the
The D28 built in amps can be an
excellent decent headphone amps and preamps .
The D-28 uses a
R-core transformer and total of 10 groups of PSU to power supplies
for all digital and analog circuits.
There are 7 groups PSU combined
double stages PSU , power supplies to the digital parts separately .
The ES9038Pro built in DA parts
had very sensitivity to the power noise and ripple . The D-28 had designed two
groups transistor serve PSU to power supply the Left and Right
parts separately ,compare to the ultra PSU chips, the serve PSU can
improve over 15DB on THD and dynamic, boost the ES9038Pro to work
performance . The Left and Right DA parts power supply separately
almost can avoid the channel crossing, makes the sound stage more
deeper and wider .
The D-28 analog
amps power supply by 2 groups high speed linear discrete transistor PSU .
That is a bit complex design than the normal PSU chips but they can
make the sound quality has better dynamic and
detail but still sound like analog that is worth to apply .
The I/V conversion volume control without sound degradation:
D-28 applies the I/V conversion volume control,
the volume control is just a variable passive I/V conversion being
placed at the ACSS amplifier output, where the output is in current
mode and not voltage mode . I/V conversion changes the volume level
from the current (I) signal to the voltage (V) signal. (Like R-2R
D/A chips output passive I/V conversion) It can keep the signal
frequency band flat while not losing any detail. It does not degrade
the sound quality at any volume level. In front of the volume
control, there are four groups of zero distortion diamond
output stages that offer very low and flat distortion output.
The D-28 applies four channels could be digitally
controlled within 100 steps relay-based volume
control built by tolerance 0.05% resistors for avoid channel imbalance
The D-28 has built in Multi-ply shield boards, to separate the
transformer, power supply, digital parts and analog parts to avoid
the different parts interfering with each other. Even the power input
IEC socket is wrapped in a copper shield .