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STAR Pure DSD DAC
Oct 2019
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To order the DIY kit or the complete assembled dac contact: hqaudiodesign@gmail.com or quanghao168@yahoo.com.vn. 1 x Star Pure DSD DAC module 1 x Controller LCD module 1 x XLR and RCA output module 1 x Silver remote This not include Amanero USB module (you can buy directly) and this not include 6.5V 20VA transformer. Total 450$ + fast shipping about 100$ to 150$ The price for the complete set assembled in the chassie like photo is 1125$. |
INTRODUCTION
The high resolution PCM at 96-192KHz 24bit offer the
possibility to have a good quality digital signal
exceeding the big limits of the CD.
The
DSD
is very different from PCM, using a sampling frequency 64 times higher
than that of a standard Compact Disc, offers a frequency response of up to
100 kHz and a dynamic range of up to 120 dB across the entire audible
range.
The
DSD on paper should be better than hi-resolution pcm like the 192KHz 24bit because the two
conversions (from and to the analog) are more simple (see
this article from Korg website) but the
AES Convention Paper 6086 and
AES Convention
Paper 5395, seems to
contradict this.
The
DSD signal can be directly used to reconstruct the original analog signal
with a
simple RC filter
but with this method we get many digital noise also using a good digital and
analog filters so forget this method.
I have lost many time and money
to test these solution, using different USB to DSD interfaces, I2S
isolators and D-type flip-flop.
The little
Lampizator and
RT audiodesign companies has
succeeded to reduce the noise and produce a DSD DAC with this method but
with some limits.
This project here
exposed has another approach, it is based on the
DSC1 that is an Open Hardware, "discrete"
delta-sigma D/A-converter developped by
Signalyst,
the DSC1 is able to convert the DSD
signal to analog without noise and without a DAC chip.
The DSC converters does
not work with a PCM signal so it is necesary
convert the PCM to DSD on the fly during playing so it is necessary
to use computers with
adequate performance.
In this project we have used the CT7302PL single
chip dual channel audio digital to digital bridge with a sample rate
converter to convert PCM signals to DSD.
HARDWARE
The core of this design is the CT7302PL with the following specifications:
After the CT7302PL chip there is the
DSC in the differential
version designed by
Pavel Pogodin
with the output transformers to filter and to convert the output in
un-balanced and balanced signal.
The
74AHCT595 are high-speed Si-gate
CMOS devices used for the serial-to-parallel data conversion.
This module use a mute
circuit to eliminate any click in the transition from one track to
another using the TS5A3167 (SPDT)
single-pole double-throw analogswitch .
This module need a AC
power supply in the range 6.5V - 7V and it can power the Amanero USB
module with a dedicated 3.3V.
On Amanero module to exclude the USB
power supply and use an external 3.3V is necessary cut a
wire or remove on-board regulator.
The USB interface used
is the
Amanero with the normal
firmware to support Native DSD.
The Controller module included in the kit use
the 16F877 chip, a 20MHz Enhanced 8K Flash
Microcontrollers.
It drive a 4 x20 characters LCD and it is connected with the I2C bus to
the CT7302PL.
A separeted power transformer is used to manage
the standby function.
OUTPUT TRANSFORMERS
The output transformers
are necessary to mix the differential signals coming from the
74AHCT595 in phase and out phase.
These are also used to give
un-balanced and balanced output signal, the module integrate a relay to
switch the ground connection.
The models has been selected by
Pavel Pogodin
after many test and also I have compared these with other models with much
higher cost always preferring these.
These have
a turn ratio of 2:1+1, made with a permalloy core with a thickness of 0.16mm and
an inductance about 340H.
The declared frequency response is 10Hz - 195 KHz
at -0.2dB for the yellow and 20Hz - 80 KHz at -0.2dB for the black type
Yellow type has more "air" and black are probably
more balanced but it all depends very much on the record or even his mood.
REMOTE
In same case it is necessary increase the output level
so use in the setting menu the V+ and -V buttons to set +6dB. +12dB or +18dB, I
suggest a max of +6dB because otherwise the distortion can increase.
There is
also a function to set an amplification of +6dB for DSD tracks because some
player give a lower level for these.
All the settings can be saved in the
EEPROM so these will be set at the next power on (press mute button on Setting
menu).
AMANERO FIRMWARE
To get the max stability is necessary set the Amanero module with the last firmware 2006be10 with DSD Native support.
1) Download the update_tools oem tool 117 and Unzip in a folder, for example on Desktop.
3) When you replug the erased device, Windows can ask about a driver.
4) Be sure to be connected to internet.
5) Run ConfigOEM117.exe and select the CPLD
firmware
CPLD_for_1081_DSD_SWAPPED
and CPU
firmware
2006be11 after press Flash CPU.
6) Replug the USB cable and if it's all ok the audio driver needs to detect the
device.
On Windows system install the
driver ASIO 1062 and verify it in the device manager.
Set on ASIO panel the latency at 15msec stanting the Amanero ASIO program.
To reduce problem during playing in the control
panel open Sound and select as default audio device another interface.
You will select the ASIO
Amanero inside the player.
SOFTWARE
This hardware is compatible with any PCM and DSD signal so to play music you can use any audio player.
MEASUREMENTS
Output at 0dB near to 1.5Vrms.
REVIEWS
STAR DSC took first place in the contest organized by the forum Vnav.
Here is the result of a test in October 2019 with a friend of mine with a lot of experience in recording and playing audio.
Yesterday evening the first serious listening test
about the new dsc module with CT7302 vs
NAA (Network
Audio Adapter) DSC module.
The quality of the last DSC
with CT7302 is very high, the same details and the same sound stage of the
NAA DSC module.
The
NAA DSC module
with the
HQplayer filters
is a little bit more softer but it is not easy define if it is more or less near
to the real sound.
Using the CT7302 with
jRiver
the sound is very natural and analog.
PHOTOS
