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|16th November 2019, 08:03 PM||#1671|
Join Date: Sep 2009
Location: Catalonia - Europe Union
Last edited by merlin el mago; 16th November 2019 at 08:21 PM.
|17th November 2019, 01:25 AM||#1673|
Andrea and me have new design dac with input Ct7302,
Please see some . Thanks
STAR Pure DSD DAC
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.
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.
The core of this design is the CT7302PL with the following specifications:
SPDIF support up to 768 KHz/32bits mode
I2S support up to 768 KHz/32bits mode
DSD support 1x/2x/4x/8xmode
DoP support 1x/2x/4x mode,throughI2S
DoP support 1x/2x/4xmode, through SPDIF
PCM SRC / ASRC fully support 32 KHz~ 768 KHz.
PCM / DSD / DoP to PCM / DSD / DoP converter with SRC / ASRC
Crystal reference clock / MCLK / DoP / Mute status output
Auto detecting PCM / DoPformat.
Auto detecting I2S / DSD interface.
Volume control with fading in/out.(+18dB ~ -110dB step 1/32 dB)
SRC / ASRC 32 bits dynamicrange(192dB), THD+N (-174dB).
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.
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.
Alixpress type 2
This hardware is compatible with any PCM and DSD signal so to play music you can use any audio player.
Here follows some player in order of sound performances.
HQPlayer by Signalyst available for Windows, Mac OS and Linux, there is a Server and a Desktop version at a cost of 145,18 euro
Daphile Audiophile Music Server for x86 hardware, it is free but it need a dedicated hardware
JRiver Media Center available for Windows and Mac OS at a cost of $49.98
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).
Output at 0dB near to 1.5Vrms.
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.
The Best DAC is no DAC http://www.audiodesignguide.com/DSC2/index.html
Last edited by quanghao; 17th November 2019 at 01:52 AM.
|18th November 2019, 12:49 AM||#1675|
Join Date: Nov 2002
|18th November 2019, 06:29 AM||#1676|
Join Date: Aug 2015
This project is under testing.
Отладка и тестирование
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|23rd November 2019, 11:21 AM||#1677|
Join Date: Mar 2015
Last edited by Ipoci; 23rd November 2019 at 11:26 AM.
|23rd November 2019, 01:53 PM||#1679|
Join Date: Mar 2015
I don't have a comparison of the sound, with or without FiFo, I built it with FiFo from the beginning ... Dac is wonderful sounding, I don't have any desire to come back to any of the very expensive dacs I previously owned...
With Iancanada McDualXO I had the opportunity to "play" with clock crystals. The original units provided by McDualXO are just decents, Crystek crystals are definitely better ... more organic sound ... slighly "rounded", then I added a Pulsar clock ... and it's perfect, precise while remaining organic
In any case I've the suspect that DSC2.5.2 output stage, perfectly match the ingress stage of my amplifier, sound is so magic ...
|26th November 2019, 11:41 PM||#1680|
Join Date: Dec 2017
You have noted the quality of resistor matters for resistor network but have you compared boards using different resistor tolerances for the network?
We know the tolerance does not effect THD but filter response between register outputs, you could say it is less important but not sure if it could be deemed unimportant.
You believe its worth using precise resistors here?
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