MicroSD Memory Card Transport Project

[Tolu]

Originally posted by EUVL
With all respect, I think you are making it more complicated than necessary. Other than the designs from Koon and ECDesign, there are many examples of SD Card Wave Players which all look very minimalistic, e.g.

http://www.omniboard.be/
(The Echo 2 will play WAV as well as MP3, I was told).

One thing in common -- they all use some versions of dsPIC33 family.
Maybe dsPIC33 is the right choice for the purpose ....


Patrick

This one uses VLSI chips, too! The main difference is the µC and playback is done through the in-built DAC of the VS10xx-chip and not with high-quality DAC like WM8741!

[Bunpei]

Originally posted by Tolu
This one uses VLSI chips, too! The main difference is the µC and playback is done through the in-built DAC of the VS10xx-chip and not with high-quality DAC like WM8741!

I was surprised with a good sound from native DAC of VS1053b when I listened to it for the first time. Clear and powerful.
It's true that external DAC chips does not give necessarily good results.

Though Patrick seems to concern the complexity in the chip, I think the precision of LRCLK pulse interval is very good. When I observed it using a 2GHz spectrum analyser, no remarkable phase noise nor characteristic spurious was found.

Bunpei

[Bunpei]

Originally posted by Bunpei

Now, we can output to generic DACs of S/PDIF input.

Recently an audiophile whose favorite music category is Classic, evaluated our VS1053b Proto Board version using S/PDIF and his high-class DAC and amplifier.
His comment is "This SD Memory Card transport sounds like a sound reproduced by analog equipment." The term, analog equipment, means a combination of LP record, LP record player, and pre-amplifier. He said his comment meant "It's a good sound, admirable."

Bunpei

[Bunpei]

Chiaki and Bunpei tried to connect their MicroSD transport to a Japanese Class-D Amplifier, RSDA-302U, a product of Rasteme Systems Co., Ltd by modifying the PCB of the amp.

The amplifier is so-called "full-digital" and uses STA 328 Class-D Amplifier chip, incorporating TI PCM2706 for USB input and Cirrus Logic CS5340 for analog line input. The amp employs I2S as its internal common audio signal path. We removed the CS5340 and a crystal for the ADC chip and connected I2S lines fo the MicroSD transport instead. Fs is 48kHz and data bit length is 16bit under this condition. MCLK is 12.288MHz.

On this amplifier product, a microcontroller, MSP430F133, sets necessary dynamic register values of STA 328 via I2C for enabling digitally implemented volume, treble, bass control functionality bulit in STA 328. As we could not hack the firmware of the MPU, an additional effort for changing BCLK signal frequency from 1.536MHz to 3.072MHz was necessary so as to maintain a compatibility with the original ADC chip. For this purpose, Chiaki added a CPLD.

Bunpei compared sounds of two different audio sources, USB and MicroSD transport and favored MicroSD transport more because it reproduces more details than USB. This result may be due to the effect of TCXO used in the MicroSD transport.

Bunpei

[Bunpei]

Originally posted by Bunpei

Chiaki and I are making a concept for the next step. My requirement is 24bit 192KHz I2S output.

Chiaki has almost completed making his new prototype board (in the left side of the following picture) for playing 24bit 192kHz WAV files. Though Bunpei has not listened to its output sounds yet, he expects a good result.


The new board has quite a different architecutre.


A. SD memory card slot is adapted instead of MicroSD memory card
B. SDHC memory card can be used
C. FAT32 readable ( in progress )
D. RIFF WAV files of 8/16/24/32 bit, mono/stereo, 32/44.1/48/88.2
96/176.4/192kHz are supported (however, no FLAC, MP3, WMA, AAC)
E. Both I2S and S/PDIF (RCA) output.
F. User interface with three button and one LED (no LCD display)

No VS1053b chip is incorporated in this version. For PCM to I2S conversion, FPGA Altera Cyclone III(EP3C25E144)[The biggest chip in the picture above] is employed.
A microcontroller is Silicon Laboratories C8051F361 (100MIPS 8051 architecture machine of 100MHz clock). It reads WAV PCM data from SDHC memory card.
For S/PDIF output, Cirrus Logic CS8406 is used with a pluse transformer, Newava Technologies S22083.

As soon as Bunpei confirms its sound, a new report will be posted here.

Bunpei

[Bunpei]

In terms of high-precision clocking, Chiaki implemented the following mechanisms in the design.

1. Two separate TCXOs, 22.5792MHz for 44.1kHz x n and 24.576MHz for 48kHz x n, are employed.
2. Two master clocks (MCLK for I2S) are from the TCXOs.
3. I2S relevant clocks, LRCLK and BCLK, are derived from the master clock by simple scalers formed in the FPGA.
4. PCM to I2S conversion is achieved in a dual clocked FIFO in the FPGA. I2S output side runs exactly synchronizing to the master clocks described above. It's independent to PCM input side clocking.
5. I2S signals are synchronized again at the last stage in the FPGA.
As a result, the intervals of I2S siginals are to be very independent to activities of the microcontroller side.

However, we have measured neither phase shift noise nor Allan Variance of I2S signals yet. Therefore, we have no objective evidence for a "low jitter" profile of this equipment so far.

Bunpei

[Bunpei]

Originally posted by Bunpei
As soon as Bunpei confirms its sound, a new report will be posted here.

Today, Bunpei received the 192kHz 24bit WAV file compatible, SDHC Memory Card Transport from Chiaki.
Chiaki is publishing his achievement on his web page (in Japanese).
http://www.chiaki.cc/Transport/sdtrans192.html
New pictures are available on his web page.
<Connected to WM8741 Evaluation board>

In this picture, S/PDIF is used, instead of I2S.

<Solder surface>

You can see 5 black power regulators and two TCXOs( two light purple rectangular components along the left margin).

Bunpei listened 192kHz 24bit sources obtained from
Hires 2L: http://www.2l.no/hires/index.html
and
Lin Records: http://www.linnrecords.com/catalogue...ate&order=desc
using Etymotic ER-4S earphones connected to WM8741 Evaluation board employing an I2S interfacing method.
His primary impression is "sounds are more smooth, fine and continuous than that of 48kHz 16bit down-sampled ones" and "less-digital taste".
Strings in orchestra are resolved well enough to enjoy them.

Chiaki is planning to design and release a new PCB board kit with necessary components. Please let us know your opinions.
bunpei<at>ta2<dot>so-net<dot>ne<dot>jp
(The improved version may have a simple LCD display.)

Bunpei thinks this kind of players including ecdesigns' one are much worth trying and listening.

Bunpei

[EUVL]

The prototype boiard is just immaculate !!




Patrick

[guglielmope]

When a kit of this reader will be available in your opinion?
It's a very interesting design.
Ciao
Guglielmo

[prinzinio]

Dear Bunpei,

have You tried to play wolfson board through USB?
Ive finally made my DAC, but Windows doesn't recognize any new hardware (tas1020b). When i plug in the usb cable i hear the specific sound in windows, but nothing apears, theres no new usb controler installed.

Does it need any drivers? Could You help me Bunpei?