Κώστας Φ.
Truth hurts. Here's a teddy bear.
- Μηνύματα
- 8.978
- Reaction score
- 895
Πριν λίγο καιρό, σε άλλο thread, θαυμάσαμε το Philips CDPro2M στο νέο player της Nagra.
Eίχα βάλει κάποιο link σε site που πουλάει το transport αυτό για DIY εφαρμογές αλλά με ένα σκέτο trasport CD player δεν φτιάχνεις.. Έχω την εντύπωση πως το θέμα DIY CD player δεν έχει "ψαχτεί" αρκετά απο τo DIY community οπότε οι περισσότεροι πάνε λίγο στα τυφλά. Χρειάζεται ψάξιμο και δοκιμές - οι οποίες κοστίζουν.
Αυτό θα σκέφτηκαν και στην TentLabs και αποφάσισαν να δώσουν ένα hi-end CDp βασισμένο στο trasport της Philips σε μορφή DIY kit. Ενδιαφέρουσα υλοποίηση που δείχνει ότι έχει αφιερωθεί χρόνος στο σχεδιασμό του, εύκολο στην συναρμολόγηση και με τιμή στα 2500 ευρώ (προ φόρων και μεταφορικών). Επίσης αναμένεται και έκδοση με USB port για να μη γκρινιάζει ο Κ.Κ.! :respect:
Για να δούμε τι έχουν να πουν οι reviewers του 6moons για το player αυτό...
Αξίζει, για αρχή, να μεταφέρω απο το 6moons μερικές τεχνικές λεπτομέρειες για τις επιλογές που έκαναν οι άνθρωποι της TentLabs (aka το αποτέλεσμα του "ψάξιματος" που λέγαμε παραπάνω και το οποίο έκαναν οι της TentLabs πριν απο εμάς για εμάς - or so they claim!):
"TentLab's goal with all products focused on CD reproduction is to rid them of 'digital sound'. This nasty habit of many playback systems is, Guido feels, predominantly caused by poor jitter handling. Guido knows first hand how jitter can be addressed and corrected when using appropriate measures. In the DIY CD player, he uses all of them. The player starts with the sturdy base of a quality drive. Many high-end manufacturers have arrived at the same choice of Philips CDpro2M. This is a top loader so a tricky drawer system was unnecessary. For the drive's servo and control logic, Guido uses two separate power supplies to avoid crosstalk between them and minimize jitter in the signal path.
Data from the drive is carried to the DAC via an I²S connection. Contrary to the routine protocol of S/PDIF, I²S is immune to data-dependent jitter effects and that, after all, is the goal at this stage. TentLabs then bypasses the standard clock incorporated in the CDpro drive. The clock used instead is the master clock located on the separate PCB of the DAC. To accept the external clock, Guido had to modify the drive, again to minimize jitter. To protect the drive from external mechanical influences, a rubber-sprung heavy metallic sub-chassis suspends it from the player's casing.
For the converter stage, Guido uses a pair of Texas Instruments PCM1704 multi-bit DACs while omitting any digital filtering. Filters tend to introduce jitter and he prefers to run the converters at 1/8th the normal clock speed instead. Both converters receive their power from analog supplies that are stabilized by four shunt regulators. Cross talk is avoided and the noise floor remains low.
TentLabs then uses proprietary interface logic to convert the 16-bit I²S data into a format that the PCM1704 is able to convert directly. Unique to this approach is how the data from the serial I²S stream -- both channels behind each other -- are split by stop-clock operation. This way only data for the channel active at that moment gets delivered to that channel. In traditional designs, what arrives at the 'active' converter is stereo rather than mono information. Do we need to mention that the incoming data signal is reclocked by the low jitter Tentlabs XO master clock prior to entering the DAC chips? The XO clock derives it power from a shunt supply.
In order to use the DIY CD player as just a spinner, a S/PDIF digital output is provided. This signal comes off the CD drive module but is re-clocked on the DAC board using the master clock. A buffer stage insures correct 75-ohm impedance and a digital transformer acts as galvanic decoupling device.
The output from the PCM1704 converters is current of course which needs to become voltage after which the voltage needs to be amplified and buffered. All this is performed by a tube-based I/V converter stage. That board carries a so-called transconductance (or current source amplifier) that outputs a current proportional to its input voltage with two active elements, a transistor and an E88CC tube. This amplifier works completely in the current domain to eliminate power supply noise. The circuit presents a sub 1-ohm impedance to the PCM1704 chips to insure low distortion. An Audio Note tantalum resistor converts current to voltage before being high-passed at 6dB/octave. Another tube, a 6x4 rectifier chosen for its musical properties, oversees the high voltage supply on the I/V board.
Inside the player, TentLabs also uses three large toroidal transformers. One is dedicated to the drive, one supplies the I/V converter board and the third the DAC board. These circuit boards use surface-mount devices and are based on Guido's know-how with EMI and signal integrity while working at Philips. They help to reduce noise in the digital to analog conversion, crosstalk and of course keep jitter at bay as far as possible. From the three power supplies clearly visible in the photos, two supply the drive, one the display."
Αρκετά με τα τεχνικά όμως... Τελικώς, αξίζει τον κόπο!?
"With a kit price of € 2,500 or roughly $3,375 without taxes and shipping, this CDP is a bargain. It can and will blow many far more expensive CDP out of the musical waters without much effort. Granted, you have to build the thing yourself or find a friend to help you. That will add a couple of hours of building joy or a little extra cost. In the end though, you wind up with a fantastically musical machine that, with the announced USB port, is even future proofed for the time when CDs will disappear in the same niche status vinyl is already said to be in now."
Περισσότερα μπορείτε να διαβάσετε στο 6moons.com και συγκεκριμένα εδώ.
