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DSC1 v2.5 - The pure DSD converter
Nov 2017

INTRODUCTION

The high resolution PCM at 96-192KHz 24bit offer the possibility to have a good quality digital signal near to the analog exceeding the big limits of the CD payer.
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 to create differential outptus like this by Hazard.   
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 is based on the DSC1 that is an Open Hardware, "discrete" delta-sigma D/A-converter developped by Signalyst able to convert the DSD signal to analog without noise.
This DSD converter does not work with PCM signal so to play any audio track it is necesary convert in DSD on the fly during playing.
There are many opinion about the PCM to DSD conversion and I am convinced of validity, here some measurements about using different output.
 
Some here also some open discussions on this argument:

RESULT

In my sonic performance tests I always search to be sure of an objective result using many persons, more systems and different environment.
This mean that the result here is not my personal and it is not subjective like many other test published online.

All the tests performed have demonstrated the validity of this converter, it is much better than Sabre ES9018.
The details are of the highest level, there is no fatigue during listening and the scenic reconstruction is amazing.
The only disadvantages are the DSD conversion on the fly that forces us to use computers with adequate performance and the necessity for a passive volume regulation after the dac becasue only HQPlayer can attenuate the level on DSD tracks. 

 

HARDWARE

The DSC1 is an Open Hardware, "discrete" delta-sigma D/A-converter developped by Signalyst able to convert the DSD signal to analog without noise.
This method allow to create a very simple DAC without a DAC chip with sonic performance much better than hi-end DACs.
At this time probably there is no commercial product using this method to convert the digital signal to analog.
Obviously the project evolved in the differential version called DSC2 and this is available as the previous on some Chinese online store.


The 74AHCT595 are high-speed Si-gate CMOS devices used for the serial-to-parallel data conversion.
Here we have a new differential version designed by Pavel Pogodin with the output transformers to filter and to convert the output in un-balanced and balanced signal.
This new module use a modified mute circuit to eliminate any click in the transition from one track to another using the TS5A3167, two regulated power supply using the TPS7A4700 and a optimized signal path. 
In order to reduce output impedance to 250ohm the 4 x 32 resistors are here 8Kohm (Sumiko RG with tollerance 0.1%) instead of the original 15Kohm.
This module need a DC power supply in the range 7V to10V and it is not necessary to be stabilised but with LowESR capacitors.
The USB interface used is the Amanero with the normal firmware to support Native DSD.

The output trasformers has been selected by Pavel Pogodin after many test and also I have compared these with other models with much higher cost.
These have a turn ratio of 2:1+1, made with a permalloy core with a thickness of 0.16mm and a declared frequency response of 10Hz a 195 KHz-0.2dB.

Now Pavel Pogodin encouraged by my positive feedback is developping a new optimized module to produce in a little series.
So now I need to wait some weeks to test it and after will be possible buy this.

preview of 2.6

 

 

FIRMWARE

It is necessary set the Amanero module with the last firmware 1099c with DSD Native support.

1) Download the update_tools  oem tool 117  and Unzip in a folder, for example on Desktop.

2) ERASE THE FLASH




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 firmware 1099c after press Flash CPU.

6) Replug the USB cable and if it's all ok the audio driver needs to detect the device.

 

SOFTWARE

This hardware is compatible only with DSD signal so to play PCM tracks is necessary a software with the on the fly convertion.
Here follows some player with this feature in order of sound performances.

All these software need a good PC for the PCM to DSD convertion so use an Intel® Core™ i3 Processor with 2.5GHz min. and a 4Gb RAM min.

 

HQPlayer

This software have many algoritm and noise filters which allow many sound variations.
At this time only with HQPlayer is possible use the volume control for both PCM and DSD tracks and increase the volume of some dB.
Follows the screenshots to follow to enable the PCM to DSD convertion and keep the volume control always active.

Here the task manager on my  Intel i5-5300M CPU @ 2.30GHz.

 

 

Daphile

This software is an operating system based on a Linux kernel optimized to create a music server and it is configurable with a web interface.
It run on 32bit or 64bit x86 hardware so any normal PC is good but this must be dedicated to this use only.
The web interface is compatibe with Apple and Android Squeezer applications available on Play store.
Both wired and wireless are supported (if these are compatible) and it can even operate in a standalone mode where it provides a wireless access point for the control device.
The volume control will be disabled if you select on audio interface panel the PCM to DSD convertion.

Follows the guide for the installation and configuration of Daphile for high-quality conversion of PCM to DSD.

1. Download from x64 version with real-time kernel support. Or the latest beta version.
2. In the BIOS of the computer, be sure to disable all built-in audio devices. 
    So Daphile will work only with Amanero in UAC2 mode and it will not use the extra ALSA layer.
    http://www.modelpromo.nl/Audio-Dandy_streamer_Daphile.htm
3. It is desirable to disable Hyper-threading support for the CPU in BIOS.
4. Write the Daphile image on a USB flash drive with any available software like Win32DiskImage or Rufus.
5. Switch-on the target PC with USB flash drive inserted and select in the bias the boot from USB.
6. During the Daphile boot press F1 and select “wipe/prepare another storage device as a Daphile installation target.
    Attention because all old data on the specified disk will be destroyed!
    You can install the system also in the same USB flash drive used to start the installation.
7. All the settings will be set in the web interface http://daphile.local so use another PC or a Tablet to open this link.
8. Installing Daphile on the internal disk: Settings->System Firmware->New Installation.

 


9. After the reboot (Save & Restart), continue to configure like show below. 

 


 

The selection of track is very simple also using web interface.

This operating system need a good PC for the PCM to DSD convertion, follows the cpu consumption on my Dell Vostro 2520 with Intel i5-3210M CPU @ 2.50GHz.

Playing a PCM track with an output rate set to DSD128 only 50% used and no problems while listening.

daphile ~ # top
top - 17:44:00 up 2 min,  1 user,  load average: 2.18, 0.95, 0.36
Tasks: 181 total,   1 running, 180 sleeping,   0 stopped,   0 zombie
%Cpu(s): 32.2 us,  7.6 sy,  6.9 ni, 24.1 id, 28.5 wa,  0.0 hi,  0.8 si,  0.0 st
KiB Mem :  8045432 total,  6102984 free,   533272 used,  1409176 buff/cache
KiB Swap:        0 total,        0 free,        0 used.  7402776 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND                                     
 5509 user      10 -10   68616  10548   4760 S  50.8  0.1   1:01.98 sox    
 

Playing a PCM track with an output rate set to DSD256 the cpu is full (98.7% used) with many lock.

daphile ~ # top
t
op - 20:27:16 up 3 min,  1 user,  load average: 2.99, 1.29, 0.50
Tasks: 179 total,   3 running, 176 sleeping,   0 stopped,   0 zombie
%Cpu(s): 54.2 us,  1.7 sy,  4.3 ni,  0.3 id, 39.3 wa,  0.0 hi,  0.2 si,  0.0 st
KiB Mem :  8045432 total,  5982912 free,   534116 used,  1528404 buff/cache
KiB Swap:        0 total,        0 free,        0 used.  7401872 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND                                     
 6894 user      10 -10   64840   9328   4920 R  98.7  0.1   1:14.77 sox                                         

 

  

JRiver

The JRiver is a media player software for x64 computers with Windows (7,8,10), Mac and Linux.
This software is able to play any high resolution tracks like flac, dff, dsf and also SACD iso images.
The internal volume does not work on DSD tracks.
Follows the simple guide to select the PCM to DSD on the fly convertion.

Here the task manager on my  Intel i5-5300M CPU @ 2.30GHz.

 

JRiver + ASIO Proxy

The JRiver is a media player software for x64 computers with Windows (7,8,10), Mac and Linux.
This software is able to play any high resolution tracks like flac, dff, dsf and also SACD iso images.
The internal volume does not work on DSD tracks.
Follows the simple guide to select the PCM to DSD on the fly convertion with ASIO Proxy, use the SDM type A or D for the best quality.

If you will use the new ASIO Proxy release follows these setting.

Here the task manager on my  Intel i5-5300M CPU @ 2.30GHz.

 

Foobar2000 + ASIO Proxy

The Foobar2000 is an advanced freeware audio player for the Windows platform.
It is necessary download some components to add to the normal installation, these are auto install parts or .dll to insert in the components directory.

Use the SDM type A or D for the best quality.

 

If you will use the new ASIO Proxy release follows these setting.

 

AK4137

This is not a software but a chip with the function of digital sample rate converter.
The my idea is develop a new firmware to control the AK4137 and integrate a volume control with R2R Shunt Volume .

The AK4137EQ is a 2ch digital sampling rate converter (SRC).

I am waiting an assembled module from China for some first test.
If the performances of this chip in the conversion from PCM to DSD will be comparable to those of the listed software this would allow the use of less performing PCs and the use of spdif sources for this DSD converter. 

Here the USB Amanero module installed on the AK4137 module and this connected to DSC1 2.5.
Some click during the track switch but this system sound good also with spdif sources.

Guide to AK4137 module:

During initial phase keep pressed the button to enter in setup menu to select the USB interface model XMOS or Amanero.

   

 After the banner will be available 2 functions with the same button:
    - Short press to switch the input channel                  
    - Long press (more than 0.5 seconds) to change the fiter and output type

1. input RCA, AES, USB, OPT, BNC
2. PCM / DSD type of input received
3. PCM / DSD input frequency
4. filter SharRoll, SlowRoll, ShoSharp, ShorSlow
5. type of output I32, R32, R24, R20, R16, DSD
6. output frequency for DSD 2.82, 5.64 and 11.2MHz,

Power supply voltage: 5V, operating current of about 100MA  

Here some measurement using this module:

and here some frequency responce with different filters

 

MEAUSREMENTS

Here the distortion at 1KHz and 1.6Vrms output.

Here the distortion at 100Hz and 1.2Vrms output.

The distortion and noise of version 2.6

 

POWER SUPPLY

In order to have all the power supply necessary for this project I have buy a power supply module on Alixpress.

High Speed Low Noise Triple Independent Linear Regulator Power Supply only 14-17$.

In the order ask for 3.3V, 5V (AK4137 if necessary) amd 7.5V and add a good 9VAC 30VA transformers.