SD-CARD player

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omudenisip
Posts: 35
Joined: 05 Feb 2009, 15:45

SD-CARD player

Post by omudenisip »

o chestie faina.ce se presupune transportul perfect in cazul CD-urilor Audio 16/44
citirea facandu-se de pe card SDHC are multe avantaje fata de un transport CD-obisnuit :
-complet silentios neavand piese in miscare
-citirea e bit-perfect de fiecare data (se extrag track-urile din CD-urile audio cu EAC direct pe cardul SD)
-nu introduce jittere aditionale datorita clockului ultra low jitter
-pe langa iesiri ordinare Spdif are I2S direct pe placa fiind compatibil a-l lega de DAC -ul preferat...pretul e ft ft bun

http://cgi.ebay.com/QA-550-Hi-End-WAV-D ... 911.c0.m14" onclick="window.open(this.href);return false;

iar un proiect DIY facut de EC Design care ii prezinta toate avantajele,denumindu-l the ultimate source

"The advantage over CD players is the bit-perfect CD image, stored on a semiconductor memory card, that's able to reproduce exactly the same digital audio data, over and over again. Unlike CD players, the semiconductor memory is insensitive to shocks and vibrations, the card is also more robust compared to a CD that damages (scratches) easily. The SD-card player is absolutely silent (no moving parts).

The SD-card capacity also allows storage of multiple CDs or even an entire play-list. Due to the clock strategy and interface (I2S out), very low clock jitter and interference levels could be obtained. The interface / interlink related problems are eliminated.

The advantage over computer (PC) based digital audio sources is the absolute silent operation, low power consumption, very low interference levels, very low jitter, and The interface / interlink related problems are eliminated.
All conventional digital audio sources, interlinks and digital audio receivers add noise, interference, and jitter signatures to the sample timing signal. This is mainly periodic jitter (worst kind). This jitter is extremely difficult to attenuate, and unless the design is absolutely perfect, jitter always finds a "back door" and pollutes the entire DAC electronics like a virus. This interference spreads though wiring, components, PCB, and wireless (EM radiation). Slaving transport or sound card helps, but it won't prevent jitter from spreading among the DAC electronics as we still require the external data signal that also contains jitter.
The problem is even worse when using external DACs. Interlink, digital audio receiver interference, and jitter are added.
The easiest way of solving this problem is to create a clean digital audio source, and integrate it with the DAC chip using I2S. That's exactly what we did with the SD-player.

How will this compare to a CD player or computer? well, it would have far lower jitter and interference levels to start with, because a lot of potential jitter and interference sources are taken out of the equation. The jitter signature can be shaped much easier, obtaining mainly random jitter.
So when the digital audio sources are constructed optimally, the SD-player concept is most likely to provide best results. "

poza cu el finalizat : http://i32.tinypic.com/2ckkn6.jpg" onclick="window.open(this.href);return false;

(topic initial http://www.diyaudio.com/forums/showthread.php?t=140538" onclick="window.open(this.href);return false;)

Obelix
Posts: 1444
Joined: 19 Jan 2009, 13:01

Re: SD-CARD player

Post by Obelix »

PENTRU MINE ar deveni interesant cand ar sti sa "cante" si alte formate lossless (...si chiar MP3, de ce nu, e si ala bun, macar ca sa stii daca un CD merita cumparat...)

omudenisip
Posts: 35
Joined: 05 Feb 2009, 15:45

Re: SD-CARD player

Post by omudenisip »

in cazul de fata se doreste puritatea cat mai mare a formatului cd-audio 16/44 care sa fie transmisa DAC-ului in cel mai perfect mod posibil lipsita de orice fel de jitter pe cat posibil.
inclusiv introducerea spre citire a formatului FLAC necesita o putere mai mare de procesare din partea microprocesorului care genereaza implicit consum mai ridicat interferente mai mari si degradeaza semnalul I2S in consecinta...EC Designs a explicat mai pe indelete cum sta treaba

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momolo
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Posts: 14156
Joined: 02 Oct 2008, 10:11
Location: Bucuresti

Re: SD-CARD player

Post by momolo »

Ca idee si teorie este interesanta. Insa adevarul nu-l putem sti decat la proba practica. Sunt multe chestii care teoretic trebuie sa sune minunat si in realitate e vai de ele. Exista si cazul invers.

Vazand acest card reader m-am gandit la playerele multiformat ce umplu supermarketurile la ora actuala si nu costa mai mult de vreo 50 euro. Majoritatea au acum cititor de carduri si iesire SPDIF coaxiala si optica. Insa nu sunt sigur ca recunosc "formatul" .wav ?!, asta ar fi problema insa stiu ca exista unele care merg si cu FLAC.

Eu am un mediaplayer PopCorn care stie (probat) de FLAC si APE. Imi pare ca nu stie de wav insa FLAC, din ceea ce stiu eu, este defapt tot wav, adica la redare se desface in wav. Rog sa fiu corectat daca gresesc.

Mai e si problema calitatii extractiei unui CD audio in fisiere wav. Din cate stiu eu (si am experimentat) aici s-ar afla problema cea mai grea, calitatea extractiei.

Daca cineva isi cumpara o jucarie din aia mentionata mai sus, eu ma ofer sa pun la proba un DAC, cablu coax digital si o amplificare de buna calitate ca sa vedem ce iese. Pana nu incercam practic nu putem afla insa personal sunt foarte sceptic in privinta calitatii.

Mai e si problema FAT16/32 care nu accepta decat fisiere maxime de aprox 4 GB.

Dar ca idee e draguta chiar si pentru faptul ca nu mai ai zgomot de PC sau de HDD (deloc neglijabile).
"Tinereţea este o noţiune, biologia un adevăr. Ele împreună dau dimensiunea existenţei"(Geo Bogza)

omudenisip
Posts: 35
Joined: 05 Feb 2009, 15:45

Re: SD-CARD player

Post by omudenisip »

dar ai tu vreo melodie CD-audio sa depaseasca 4 GB?
chiar daca e un mixaj si e o singura melodie pe tot CD-ul nu poate depasi 700 MB si oricum inca sunt destul de scumpe cardurile SD de 16/32 GB - asa ca e suficient unul de 8 GB sa pastrezi pe el material de vreo 11-12 CD-uri.
EC Designs e un perfectionist care construieste aparate pe comanda (electronic custom designs) are si pagina net la adresa

http://www.ecdesigns.nl/dacs/di8m/di8m.html" onclick="window.open(this.href);return false;

daca urmaresti topicul sau Building the ultimate NOS DAC using TDA1541A,vei vedea ca omul e plin de idei noi inovatoare care le aplica la acest DAC antic si care-l sa "cante" cu adevarat comparativ cu oricare hi-end de azi

http://www.diyaudio.com/forums/showthre ... 2&page=302" onclick="window.open(this.href);return false;


"Most digital audio sources fail to provide bit-perfect playback by default. Computer-based digital audio sources often require extensive and repetitive tweaking (software updates). There are even some CD players / transports that fail to provide bit perfect playback (digital volume control). Interference present in the digital audio source will translate to jitter on the digital audio signals. So even a Toslink interface can transport digital audio source interference in the form of jitter / jitter spectrum. If the electronics in the DAC fail to completely block this jitter, it means source interference will still end up in the audio signal.

It would help a lot if the digital audio source would offer guaranteed bit-perfect playback and a cleaner digital signal (containing less interference / jitter) to start with. That way it's easier to achieve required low jitter / interference levels at the DAC.

Other problems relate to digital transmitter, interlink, and digital receiver. Usually SPDIF or USB are used to transport the digital audio data between source and DAC. Since these digital interfaces have known flaws, using them means making compromises.

In order to avoid these compromises in the first place, it's best to not use these digital audio interfaces at all (if possible), but this means integrating both digital audio source and DAC, using DAC chip digital interface like I2S for example.

So it would be beneficial to integrate both digital audio source and DAC while making sure the digital audio source provides cleanest possible signal (extreme low jitter / interference).


This resulted in designing a digital audio source from scratch, the lossless SD-player (semiconductor memory -based digital audio source).

The digital audio data is stored on a SD/HC memory card without compression using WAV format, this way the data remains transparent and exactly matches with the data on a CD. Interference produced during conversion (FLAC > WAV) that requires increased processing power is avoided. The data stored on the SD/HC card is output in the form of a I2S signal. The trick is to keep processor interference as low as possible, this was done using a low-power processor (nanowatt technology) that only consumes approx. 250mW under full load.

The clock signals were derived from a single ultra low jitter master clock that uses 3 selected / matched crystals. In order to maintain extreme low jitter levels, clock loads were reduced to only 2, and clock buffers weren't used as these would add extra jitter. One clock load is formed by the processor. The second is a high-speed flip-flop that synchronously reclocks the already low jitter BCK signal (I2S) from the processor. This method turned out to work better (lower jitter) than using a synchronous divider. The ultra low jitter clock then enters a dynamic jitter attenuator that further reduces the effects of jitter on sample timing.

I2S usually holds 64 bits/frame, 32 for L channel and 32 for R channel, but when using 16 bits for each channel only, 16 bits remain unused and have to be set to some value, usually zero. This then results in repetitive pulse bursts of 16 bits containing digital audio data and 16 bits containing zero. This will introduce interference (asymmetrical signal). In order to avoid this, the SD-player uses 32 bits/frame, 16 bits of L channel, immediately followed by 16 bits of R channel, creating a more symmetrical signal. Other advantage of this method is that bit clock could be lowered to absolute minimum value for 44.1/16 I2S namely 1.4112 MHz.

As stated before, the DAC is now integrated with the source and is directly connected through I2S, avoiding SPDIF/USB "issues".

Passive I/V conversion (resistor only) was used to completely avoid distortion produced by active devices.

In order to achieve lowest possible interference, very low noise power supplies had to be used. These consist of a battery power supply followed by low pass filters and voltage regulators. Noise levels then drop well below 205dB.


The SD-player is now completed and performs beyond expectation, in fact it performed so well that it revealed flaws in my audio set, forcing me to redesign volume control, power amplifiers and speakers before continuing. This took quite some time.

Volume control is a plain high quality potentiometer, relay contacts (depends on properties) will add subtle distortion, so the relay volume controls could no longer be used.

The MOSFET power amplifier failed to provide required resolution (low volume settings), so I designed a straight-forward, fully DC-coupled all-FET balanced bridge power amplifier. This amplifier has no global feedback, no constant current sources, no current mirrors nor DC-servo. The schematic is very simple (4 JFETs, 4 power MOSFETs, some resistors, few diodes, and a straight forward power supply (rectifier + smoothing caps). The amplifier accepts both balanced and single-ended input signals. Gain is rather high (bridge configuration) approx. 100x.

The 3-way speakers (omnidirectional, and based on the sonic resonator system) turned out to be limiting performance too. I now developed a new semi 2-way system that performs much better.

I attached a picture of the new prototype setup and new sonic resonator. It's a messy prototype setup for testing only.


So now I can finally continue with TDA1541A-based DAC development. needless to say that this DAC has to be driven by a SD-player using SD/HC memory cards.

The surrounding circuits for the TDA1541A were already discussed on this thread. I plan to use I2S attenuators, LED voltage regulators for +5V, -5V, and -15V, the latest DEM clock circuit (referenced to -15V using level translator). The decoupling caps (100nF) will be located underneath the chip for shortest possible connections.

I plan to use balanced output configuration, and since my power amplifier has relatively high gain, I could get away with true passive I/V conversion without any active components, producing say 300mVpp on each output. I plan to achieve this with the split I/V resistor circuit that includes a small bias current for manipulating TDA1541A output compliance, this way up to 550mVpp can be generated at the DAC outputs, maintaining low distortion. Combined I/V resistor value for each of the 4 outputs will need to be approx. 0.3 / 0.004 = 75 Ohms, so I could settle for 2 x 39 Ohms. This will also provide low output impedance.

The signal would then enter a quad volume potentiometer, and would be fed to the balanced inputs of the power amps. This way there is only one active circuit (power amplifier) between DAC output and speakers. Depending on DAC DC offset trimming I could get away with a fully DC-coupled system (no coupling caps at all). This would help to further reduce distortion.

So the ultimate NOS DAC project will probably result in a lossless SD-player with integrated, highly optimized TDA1541A-based DAC in dual mono configuration (requires 2 x TDA1541A/S1/S2).

About the interpolation (4x, 8x, 16x) used in earlier designs, this is no longer required when the digital audio source is virtually perfect (extreme low noise and jitter) and the connected audio equipment is able to handle the resulting unfiltered signal (audio spectrum plus reflected mirror images). Required brickwall filtering at approx. 20KHz will now be performed by the human auditory system. Just for clarity, I use no analogue filtering at all, except for the passive crossover filter in the speakers and the mechanical limitations of the speaker chassis."


http://i29.tinypic.com/107tkz6.jpg" onclick="window.open(this.href);return false;

http://i32.tinypic.com/ayvi1h.jpg" onclick="window.open(this.href);return false;

Obelix
Posts: 1444
Joined: 19 Jan 2009, 13:01

Re: SD-CARD player

Post by Obelix »

Pretul nu mi se pare imens, calitatea... nu poti decat sa speri... reiterez insa criticile formulate anterior: lipsa unor alte formate decat VAW.
Fara sa admit explicatii in stil Bill Gates ( "It is not a bug, it's a feature" ), adica in cazul de fata, "frectii" academice despre puritatea sunetului...
Daca trebuie sa stau la calculator 2 ore pentru 1 ora de auditii, nu vad "progresul", un CD Player cu 1541A se da la 50 de Euro...
Ma rog... parerea mea...

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