The project was born from the idea to always have
all my software (music) with me in any place. Obviously who knows to me
will never imagine that I am talking about a portable MP3 player
because I want the same sound quality as the original CD.
A test done with the EAC free software (Exact
Audio Copy from http://www.exactaudiocopy.de/
) demostrated that the PCM files (.wav) extracted with this
audio grabber could be better than original.
Given that situation, I decided to have a look in
the portable PC market for the storage solutions.
The current 2.5" technology for portable hard disks with USB 2.0 or
Fireware interfaces is available on the market up to a capacity of 80GB
with a reasonible price. These disks are smaller than their 3.5" mates,
with a noticeable plus: no need for a separate power supply, because
they get energy from the USB connector.
Wiithin a 80GB disk we can suppose to store a max of (80GB /
600MB) 133 CD. Such an amount is not enough for the 'normal'
audiophile, at least it is not enough for me! In my opinion a
significant amount of CDs is around 500 (BTW, strange but many people
involved in audio diy, or even interested in hi-fi / hi-end equipment
will spen alot of money in electronics, and not so much in music CDs ..)
In order to store more CDs I searched the Internet for a lossless audio
compressor, geting a relevant result:
Here the main feature description from the TTA website:
'TTA codec performs lossless compression on
multichannel 8,16 and 24 bit data of the Wav audio files. Being
"lossless" means that no data/quality is lost in the compression - when
uncompressed, the data will be identical to the original. The
compression ratios of TTA codec depend on the type of music file being
compressed, but the compression size will generally range between 30% -
70% of the original. '
Not bad, at this point I decided to perform a quick test to check
if I can 'rebuild' the original PCM file (.wav) with such a procedure:
The encoder is very easy to use because you need only to start in the
Windows command line the program ttaenc.exe with the following syntax:
ttaenc
-e [input file] -o [output file]
To open the Windows command line follows
these simple pictures.
Select Run in the main menu and
type cmd or command in the Run window.
The cd command following by the directory name will be use to enter the
target directory of your disk.
In order to speedup the process of storing all the TTA compressed files
in the hard drive, it is possible to integrate the TTA encoding in the
EAC software with the following setup:
Setting these option the EAC software will automatically compress any
extracted file with the TTA encoder, leaving in the target directory
just the compressed files.
With this solution is resolved any problem of reading errrors and
degrade of quality of the CD.
Offcourse the sound quality of normal PC audio interface is low and we
want a true Hi-End quality.
Exploring the commercial products of the external audio interfaces I
have found and tested all these choices:
Audiophile USB
is a compact audio and MIDI interface that builds on the success of our
popular Audiophile 2496—awarded Best Soundcard by Computer Music
magazine. AC-powered components allow Audiophile USB to deliver some of
the best fidelity, frequency response, dynamic range and noise specs
available in a USB interface. You also get digital I/O for pristine
transfers, as well as the ability to pass AC-3 and DTS surround sound
signals. MIDI I/O rounds out a great compact interface that’s easy to
take anywhere you want to take your music.
This interface give this features:
USB connectivity for audio and MIDI
2 pairs of analog line-level audio inputs (1/4" unbalanced or
RCA)
2 analog line-level audio outputs (RCA) with level control
S/PDIF in and out (coaxial)
Support AC3 for surround sound setups
MIDI in and out
Headphone output (1/4") with level control
The external power supply should promise an higher sound dynamic than
bus-powered circuitry
Small
enough to fit in your pocket, Transit brings hi-resolution 24-bit/96kHz
recording and playback to any USB-compatible computer. Digital I/O lets
you transfer pristine audio between your computer and other devices
such as MiniDisc and DAT. The digital output can deliver AC-3 and DTS
from your computer to an external decoder such as a surround receiver.
And the bus-powered design allows you play and record virtually
anywhere your laptop can go. Transit is your ticket to ride.
This interface give these features:
Mobile 24-bit/96kHz USB audio
1/8” stereo analog/optical digital input
1/8” stereo line/headphone output
TOSlink optical digital output allows AC3 and DTS pass-through
OPTOPlay is the unique, yet simplistic USB device for high
quality analog and digital output. Simply plug OPTOPlay into your PCI's
USB port and instantly listen to 24-bit 96kHz professional quality
audio.
OPTOPlay brings you to the amazing world of Dolby Headphone Technology,
a unique signal-processing system that enables your stereo headphones
to portray the sound of a five-speaker, surround-sound playback system.
With Dolby Headphone Technology, sounds that were designed to come from
all around you are actually heard that way and not out of each side of
the headphone.
OPTOPlay's compact design and high-fidelity headphone amp delivers the
ultimate portable audio solution with professional
This interface have these features:
Hear Crisp, Virtual Surround Sound via Dolby Headphone Technology
24-bit 96 kHz Professional Quality Audio
Clear Analog Stereo Output
Optical Digital Output for MiniDisc Recorders and Other Digital
Devices
The output stage use the MS6308
by MOSA ELECTRONICS
CORP (http://www.mosanalog.com.tw)
a Class AB Stereo Headphone Driver compatible
with the Philips, TDA1308T.
I have found on the Head-Fi forum (http://www.head-fi.org/) an easy
modification about this interface by doobooloo user
to skip the output stage and get the
signal directly from the DAC chip (click to enlarge).
This upgrade is a sure step to increase the sound quality but after
this modification is no more possible use the Optoplay to drive
directly headphone.
The DAC included in these products have not the same specifications of
the last generation reference chips like AK4393. AK4394, AK4395 or
AK4396 but in any case the quality is very good.
To drive my headphone Beyerdynamic DT 880 with an impedance of 300ohm
the best since to be the Optoplay probably because is the unique with a
true headphone amplifier.
But the Audiophile USB is the unique with enogth output voltage to
drive the my headphone.
The my idea is to use the Optoplay or the Transit excluding the output
stage and build a true hi-end tube amplifier.
CAR SOLUTION
The car solution to play the TTA files stored in the my
portable hard
disk is a PC with serial LCD display and simple keyboard.
I have develop a software in Visual C++ to navigate in the directory of
the PC with only few key (4 are necessary) and display the status in a
serial LCD display (4 rows x 20 columns).
The first selection is the
harddisk,
the second the directory and after
the album. An arrow indicate the
current position.
key 2 to go up
key 8 to go down
key 5 to enter in the direcoty or play
key 4 to go one level back
To debug the code I have implemented in the software also a simple
interface windows.
You can use any VIA Mini ITX
motherboard to create a car PC with any type of Windows version or you
could use my solution:
The Vortex86-6082 used is a very little board with a size of only 100 x 66 mm
including all the functions of a normal PC: vga, usb, serial,
mouse and keyboard ports, IDE controller and 128Mbyte of RAM.
Offcourse the cpu clock (166MHz) is a little low if compared to new
generation pc but for this use is enougth.
Tha my first idea was use a Linux with a opimized kernel but I have
found some problems using my USB Audio device.
With both the sound architecture: ALSA and OPENSOUND there was some strange
interruption of music also if the cpu load was load (about 30%) and
also using high nice or realtime kernal patches and set.
The 2.5"
80GB hard disk has been connected to the ide port with a simple 44 pins
flat cable to create a very compat object.
Leaving linux the alternative on low perrfomances boards is the Windows
CE and the new Winows XP Embedded.
The Windows CE is best
choice in this cases but have no USb audio support so Windows XP Embedded
has been the choice.
Windows XP Embedded is a componentized version of Windows XP
Professional that contains all of the features, functionality, and
familiarity of Windows XP Professional. Windows XP Embedded enables you
to rapidly develop reliable and full-featured connected devices. By
supporting standard hardware and software, Windows XP Embedded makes it
easier and less expensive for you to build a run-time image.
