Two-channel Digital Interpolation Filter and data in-phase processor
for digital audio.
208-pin PQFP package, Manufactured on 300-mm wafers using, 90-nm
low-k dielectric process. Devices offer advanced features for
high-performance digital signal processing (DSP) applications with
up to 250-MHz.
Data and Master-clock in-phase processing just without jitters.
Core power supply voltage: 1.2V.
I/O power supply voltage: 3.3V.
Programmable Functions: hardware control mode.
Two-channel 1-times / 2-times / 4-times / 8-times oversampling ,
supports Bypass mode (NOS mode.).
Three-stage linear-phase ( group delay distortion : Zero) FIR
¡V50dB / -90DB / -130DB.
Passband Ripple: within
Input Data Formats: I2S
Input Word Length: 16, 20, or 24 Bits
Output Word Length: 16, 20, or 24 Bits
Output Data Formats: MSB-First, Binary Two¡¦s
Sampling Frequency: 32kHz to 96kHz( In DAC Reference One/Two ,
because they Applied DIR9001 receiver chip, so only
Supports 24 Bits,
Supports 24 Bits, 96 kHz Sample Rate
Clock Autodivide Circuit Supports four Master-Clock Frequencies :
Built-in two groups high performance PLL , supports low jitter
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 2005, have evolved the technology to include all
audio signals in our systems from the digital source to the power
amplifier. Since 2006, ACSS comp5nts have become Audio-gd's most popular
The Reference-7.1 is a real fully
balanced discrete design. Applies the 8 Pieces Expensive high-end grade PCM1704UK which can support up to
24Bit/96KHz input . Similar to other PCM1704UK designs , we applied Non-feedback ACSS
analog stages. The
8 pcs PCM1704UK 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
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.
The output buffers are
Non-feedback. For low impedance, we applied the dual FET buffer output stage
which is quite less colored than most conventional circuits.
DAC Reference 7.1 has built in DSP-1
processor, which is a Two-channel Digital Interpolation Filter and
data in-phase processor for digital audio. This Device offers
advanced features for high-performance digital signal processing (DSP)
applications up to 250-MHz. Data and Master-clock in-phase
processing are without jitters. So DAC Reference 7 can offer a clear
and focused soundstage, apart from accurate and neutral reproduction
of the recorded disc/music.
Theoretically when using the DSP1, data
will be running parallel, achieving near zero jitter state, but
degrade on sound quality not only the jitter, there are some lot
reasons can effect the sound quality, so better source sound better.
But the DSP-1 can process the data better than typical digital
processor chip like PMD-100, DF1704 etc, through some experiment,
although we could perceive the sound quality difference between
differently priced and level of sources , final result shows that using entry level CD
transport or hypermarket grade DVD player, the improvement of sound
quality is huge compared to
PMD-100, DF1704 etc.
Reference-7.1 applies the excellent
8 pcs PCM1704UK
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.
total 21 PSU
groups are applied.
19 groups of high-quality class A parallel
connection PSU with dedicated DC supply double-stage PSU, which can
offer very clear DC power for the DAC,
a very black background and neutral sound characteristic. The
double-stage 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.