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Hi-Resolution Systems
        
May 7 st , 2010

 
INTRODUCTION

After 20 years spent trying to get the best signal from a digital source, developing many DACs, I have decided to convert to analog sources.
The analog sources has many problems like the noise, the low dynamic and a very short life time of the disk.
After some test on high resolution audio tracks I have decided to start this project.
There are 2 main type of high resolution audio tracks:

To play the 96/192KHz 24bit audio files it is necessary a PC and a software like the freeware Foobar 2000 because Windows Media Player is not able to play files over 96KHz .
In  these my first tests has been used an EMU 0404 USB, the my last amplifier 813 SE and the loudspeakers  The Monitor 2.
I consider good and very near to an analog source only the 192KHz 24bit stored in any lossless audio format like the Flac.
If you have a good sound card you can make some simple test with the free tracks available on 2L website.
The second type of high resolution audio tracks are the DSD present in SACD.
Using a sampling frequency 64 times higher than that of a standard Compact Disc, Super Audio CD 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 tracks on paper should be better than 192KHz 24bit so I have decided to test both the technologies.
I have found a good explanation of the DSD on Korg web site, see here.
Follows a table to see the check the
amount of information present on each format.
A 40Gb hard disk can contain:

60hours@44.1kHz/16bit/2trk   CD
16hours@96kHz/24bit/2trk      High resolution
8hours@192kHz/24bit/2trk      Top high resolution
14hours@2.8MHz/1bit/2trk      SACD DSD normal
7hours@5.6Hz/1bit/2trk           Hi-end DSD

For the DSD section click here

For the EMU 0404 USB section click here
 

Hi-Resolution Systems 192KHz 24bit

The main choices are:

  1. no spdif line, direct USB
  2. no oversampling
  3. no digital filter
  4. no up sampler
  5. sync or asynchronous re-clock
  6. passive I/V converter
  7. single ended vacuum tube output stage without feedback
  8. all shunt regulators


USB to I2S module

If we want use the PC to store audio files and ear these with a hi-end DAC like my DAC End or DACEnd 2 is possible use an USB to SPDIF created with a single chip PCM2704.
This type of converter could be created using the Kit/2 by HagTech at only 49$ and no driver will be necessary.
This solution is valid only for low resolution files at 16bit 44KHz  (CD quality) but to play high resolution files at 192Hz 24bit it is necessary a custom driver and a dedicated USB interface.

Group buy

On the market I have found these 2 products for this use:
 

 

M2Tech hiFace

The
M2Tech hiFace interface has been conceived to obtain the highest quality digital audio signal using a PC or MAC.
hiFace input format is a data stream signal with sampling frequency/resolution up to 192kHz/24bits, available from a PC or MAC USB port.
Internal very low jitter oscillators and proprietary drivers allow for playing 192kHz/24bits audio files that feature the best signal quality.
cost about 150$
Musiland Monitor 01

The Musiland Monitor 01 is available in two versions: with spdif and toslink outputs or with an internal DAC so analog outputs.

To develop an extreme performances DAC with USB input the conversion of the digital signal in spdif is not necessary and it can add only problems.
cost about 70$

M2Tech M2TOEM-01 - USB-I2S ADAPTER only for OEM

  • Up to 192kHz sampling frequency

  • Up to 24 bits resolution

  • USB 2.0 device

  • Low jitter on-board oscillators

  • Kernel streaming and direct sound operation

  • Compatible with Windows XP, Vista and MacOS

  • Accepts all common high-quality files’ sampling frequencies: 44.1, 48, 88.2,96, 176.4 and 192kHz

  • LVCMOS I2S output

cost about 70$

Xmos - USB Audio 2.0 Reference Design
  • Event-driven XS1-L1 128TQFP device
  • USB 2.0 High Speed and Audio Class 2.0 compliant
  • 1Mbit SPI FLASH with optional secure boot
  • Digital audio interfaces including I2S and S/PDIF
  • Asynchronous mode providing low latency and bit perfect digital audio
  • Audio DSP algorithms
  • Supports Windows

cost about 150$

Xmos - XS1-L1 chip for USB Audio 2.0
  • USB 2.0 High Speed and Audio Class 2.0 compliant
  • Digital audio interfaces including I2S and S/PDIF
  • Asynchronous mode providing low latency
  • Audio DSP algorithms
  • Supports Windows

cost about 7-9$

Creative CA0189 only for OEM
  • Dual switched XDIF (S/PDIF or C/DIF) inputs which support up to 96 KHz. programmable 20 or 24-bit audio word, w/HW sample rate tracking support, and NRZ user bit decoding.

  • Quad XDIF (S/PDIF or C/DIF) outputs which support 44.1, 48, 96 and 192kHz, programmable 20 or 24-bit audio word

  • 6 I2S inputs which supports 48, 96 and 192kHz, 24-bit (two of these inputs are muxed with GPIOs)

  • 6 I2S outputs which support 48, 96, and 192kHz 24-bit (two of these outputs are muxed with GPIOs)

cost unknown

XtremeUSB  XD1014 - LQFP64
  • Total 2 input and 2 output audio channels with S/PDIF output
  • Mode A: 1 x I2S I/O + S/PDIF output / (Stereo 24bit/192kHz)
  • USB 2.0 Hi-Speed compliant & USB Audio Class 2.0 supported
  • 32 bit resolution audio format support & sampling rates up to 192KHz
  • XTC; external clock technology. "no jitter anymore"
  • S/PDIF TX & RX or AES/EBU and ADAT I/O supported
  • XtremeUSB32/64 Extreme Audio Driver for Windows XP, Vista, and Windows 7 
  • Compatible with native Mac OS X Core Audio Driver
  • 'Direct I/O' kernel level audio driver support for kernel level audio processing

cost unknown

XtremeUSB XD1014 EVB
Chess Lim of the XtremeUSB are developping an USB interface called XD1014 EVB.

It will be available for the shipment in two weeks and It will work at 192kHz 24bit.

It has Optical in out for SPDIF up to 96kHz but and it have 192kHz if we wire for coaxial.

It support driver for Windows XP, Vista and 7 for both 32bit 64bit and Mac is for Snow Leopard only.

XD1014 EVB has oscillator to generate the Master Clock

I have asked to have a dip connector to get the I2S signals.

The price is still to define by XtremeUSB . 

 

VIA Vinyl EnvyUSB 2.0 Audio Controller
  • USB 2.0 High-Speed (480 Mbps) Device Compliant
  • Up to 24-bit, 192kHz sample rate
  • 8 I2S Input
  • 8 I2S Output
  • 16/20/24-bit
  • 32 / 44.1 / 48 / 88.2 / 96 / 176.4 / 192 kHz
  • 2 Stereo SPDIF Output,

cost unknown

I

 

 

SHIFT REGISTER

Following the I2S specifications the transmission of the two channels (left and right) are sequential on a unique wire.
This mean that if we connect a DAC directly to the I2S bus one channel will play first of the other.
In the most of DAC, including the AudioNote with AD1865, this problem is not considered.
This delay is about 11.34Ás @ 44.1kHz, less at 192kHz, and it must be considered in high end realization also if the negative effect could  be ear only on headphone (reference Eric Juaneda, regal and vzs on DiyAudio).
To remove this delay it is necessary use a shift register like the one used by:



DIGITAL FILTER

none, after the experience on my DAC End and DACEnd 2 I have decided to follow also for this project the philosophy of Ryohei Kusunoki.

OVERSAMPLING

none, like previuos

UPSAMPLING

none, if the choice is to use no oversampling, also the up sampling created using a sample rate converter like the AD1896 must be avoided (reference of Marek on DiyAudio)

DAC

To get the best performances the choice is the PCM1704 considered by many DIY like the best.
Others DAC like the Crystal CS4397, the Wolson WM8740, Analog Device AD1955, Burr Brown  PCM1798 cannot be considered because have an internal digital filter and an active I/V converter.
 

VACUUM TUBE OUTPUT STAGE

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