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Care tip de DAC e mai bun intr-un CD player ?
Last Updated: Sep 12 2014 14:33, Started by
Ion_de_la_Raion
, Aug 31 2014 23:20
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#1
Posted 31 August 2014 - 23:20
OK, sint convins ca multe inscrisuri de pe CD playere sint trambite de marketing, dar, din cate am citit, exista mai multe moduri de a implementa un DAC intr-un CD player. Daca ai de gand sa folosesti DAC-ul acestuia si sa nu scoti digital sunetul spre amplificator folosind DAC-ul acestuia, invariabil vei folosi una din tehnologiile existente. Dar care e mai buna ? Exista diferente in sunet ? Sint sesizabile cu urechea sau percepute doar de aparate ? Sint efect placebo sau mai mult sau mai putin suna toate la fel ? Stiu ca deschid cutia Pandorei si e mult subiectivism, dar ma intereseaza subiectul, fiind in cautarea unui player cu un DAC cat mai bun.
Pana acum am intalnit asa: - 20Bit Lambda Super Linear Converter (asta are aparatul meu curent, un Denon) - 1 Bit PWM/ACCUPULSE (intalnit in unele modele Onkyo) - M.A.S.H. Multi-stage Noise shaping (intalnit la Technics de ex.) Sint sigur ca sint si altele. Deci, care e treaba cu ele ? Care e mai bun, mai eficient, etc. Edited by Ion_de_la_Raion, 31 August 2014 - 23:21. |
#2
Posted 31 August 2014 - 23:36
DACul, in sine, este un circuit integrat produs de X si cu diverse caracteristici electronice. Pe langa caracteristici, care pot influenta calitatea sunetului, in Hi-Fi se mai pune accent pe tactarea DACului (calitatea semnalului de ceas catre el) si pe filtrele analogice folosite dupa el.
La ora actuala, unul dintre cele mai bune DACuri este WM8741 de la Wolfson, alaturi de ESS SABRE-2M cu ES9018. |
#3
Posted 01 September 2014 - 00:41
Posibil, dar eu nu am cerut un model, o firma anume, ci care tip de DAC, care tehnologie dintre cele existente e mai buna.
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#4
Posted 01 September 2014 - 08:32
Nu exista o regula prestabilita. Bine inteles ca exista chipset-uri mai performante si mai putin performante. DAC-ul(chipsetul in sine) ,paradoxal nu are o pondere covarsitoare in lantul audio. Conteaza emorm de mult felul in care este implementat acesta . Sunt cazuri in care exact acelasi chipset pus in contexturi diferite(CD playere diferite ,DAC dedicat de diferite firme,etc) sa dea un sunet foarte diferit la auditie. Parte de transport bit ,alimentari ,clock-ul si mai ales etajul analogic "de dupa" DAC ce da exact culoarea si caracterul sunetului comteaza mai mult in ecuatia finala.
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#5
Posted 01 September 2014 - 10:58
Ce e ciudat e ca producatorii nu se lauda niciodata cu etajul analogic din final, ci mereu cu titluri pompoase din zona digitala.
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#6
Posted 01 September 2014 - 11:16
#7
Posted 01 September 2014 - 13:02
Alea ce mai sint ?
Mai am unul: - 27Bit Accumulating Digital Filter-Four Times Oversampling (Philips CD-630). Chiar conteaza toate dracoveniile astea ? Stiu importanta partii analogice, dar vad ca producatorii tot chestii de DAC picteaza pe mastile aparatelor, nimic despre analog. In plus, la date toti dau banda de frecvente (nu stiu de ce se mai obosesc, pentru ca e aceeasi pentru toate aparatele), dinamica, raportul semnal/zgomot, distorsiunile de nelinearitate, separatia intre canale si variatiile wow and flutter (pe care insista sa le mentioneze ca sint sub capacitatile de masurare). Nici unul nu mentioneaza nimic de preamplificator (cu ce e construit), alimentarea, transportul, solutii constructive, etc. Toti scriu aceleasi lucruri, care sint oricum dincolo de capabilitatile de percepere ale omului de rand la toate playerele. Si cu toate astea sint playere de 200 euro si playere de 20.000 euro. Pana si la alea scumple tot aceleasi date sint trecute (nu ma refer la cele de zeci de mii, ci la preturi sensibile, sa zicem 2-3 mii de euro). Tot aceleasi date nesemnificative. |
#8
Posted 01 September 2014 - 13:17
Nu te mai uita la bazaconiile printate pe carcasele aparatelor. Vezi ce tip de DAC/ chip folosesc și informează-te despre cum este implementat chipul respectiv (filtrare, etaj analogic, alimentare ...)
Și specificațiile tehnice sunt cam degeaba (banda de frecvențe, dinamică, etc). Ion_de_la_Raion, on 01 septembrie 2014 - 13:02, said:
Alea ce mai sint ? FPGA = e un chip programabil, producătorul aparatului își programează filtrele și algoritmii de conversie - http://www.xilinx.co...ications/audio/ R2R - http://www.tek.com/b... |
#10
Posted 09 September 2014 - 20:16
uite aici o listă foarte bună cu ce chipuri și ce transporturi conțin foarte multe modele de DAC-uri și CD-playere:
http://www.dutchaudi...erter_list/#top |
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#11
Posted 09 September 2014 - 20:52
Asta nu ma ajuta. Sint modele, nu tehnologii implementate.
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#12
Posted 10 September 2014 - 08:26
Tehnologiile implementate au mare legătură cu modelul de chip conținut de CD-playerul sau DAC-ul respectiv. Mai degrabă m-aș uita la chipul din aparat decât la bla-blaul scris de producător pe carcasa aparatului
Uite, mai bine te uitai pe Wikipedia : Quote
DAC types The most common types of electronic DACs are: The pulse-width modulator, the simplest DAC type. A stable current or voltage is switched into a low-pass analog filter with a duration determined by the digital input code. This technique is often used for electric motor speed control, but has many other applications as well. Oversampling DACs or interpolating DACs such as the delta-sigma DAC, use a pulse density conversion technique. The oversampling technique allows for the use of a lower resolution DAC internally. A simple 1-bit DAC is often chosen because the oversampled result is inherently linear. The DAC is driven with a pulse-density modulated signal, created with the use of a low-pass filter, step nonlinearity (the actual 1-bit DAC), and negative feedback loop, in a technique called delta-sigma modulation. This results in an effective high-pass filter acting on the quantization (signal processing) noise, thus steering this noise out of the low frequencies of interest into the megahertz frequencies of little interest, which is called noise shaping. The quantization noise at these high frequencies is removed or greatly attenuated by use of an analog low-pass filter at the output (sometimes a simple RC low-pass circuit is sufficient). Most very high resolution DACs (greater than 16 bits) are of this type due to its high linearity and low cost. Higher oversampling rates can relax the specifications of the output low-pass filter and enable further suppression of quantization noise. Speeds of greater than 100 thousand samples per second (for example, 192 kHz) and resolutions of 24 bits are attainable with delta-sigma DACs. A short comparison with pulse-width modulation shows that a 1-bit DAC with a simple first-order integrator would have to run at 3 THz (which is physically unrealizable) to achieve 24 meaningful bits of resolution, requiring a higher-order low-pass filter in the noise-shaping loop. A single integrator is a low-pass filter with a frequency response inversely proportional to frequency and using one such integrator in the noise-shaping loop is a first order delta-sigma modulator. Multiple higher order topologies (such as MASH) are used to achieve higher degrees of noise-shaping with a stable topology. The binary-weighted DAC, which contains individual electrical components for each bit of the DAC connected to a summing point. These precise voltages or currents sum to the correct output value. This is one of the fastest conversion methods but suffers from poor accuracy because of the high precision required for each individual voltage or current. Such high-precision components are expensive, so this type of converter is usually limited to 8-bit resolution or less. Switched resistor DAC contains of a parallel resistor network. Individual resistors are enabled or bypassed in the network based on the digital input. Switched current source DAC, from which different current sources are selected based on the digital input. Switched capacitor DAC contains a parallel capacitor network. Individual capacitors are connected or disconnected with switches based on the input. The R-2R ladder DAC which is a binary-weighted DAC that uses a repeating cascaded structure of resistor values R and 2R. This improves the precision due to the relative ease of producing equal valued-matched resistors (or current sources). However, wide converters perform slowly due to increasingly large RC-constants for each added R-2R link. The Successive-Approximation or Cyclic DAC, which successively constructs the output during each cycle. Individual bits of the digital input are processed each cycle until the entire input is accounted for. The thermometer-coded DAC, which contains an equal resistor or current-source segment for each possible value of DAC output. An 8-bit thermometer DAC would have 255 segments, and a 16-bit thermometer DAC would have 65,535 segments. This is perhaps the fastest and highest precision DAC architecture but at the expense of high cost. Conversion speeds of >1 billion samples per second have been reached with this type of DAC. Hybrid DACs, which use a combination of the above techniques in a single converter. Most DAC integrated circuits are of this type due to the difficulty of getting low cost, high speed and high precision in one device. The segmented DAC, which combines the thermometer-coded principle for the most significant bits and the binary-weighted principle for the least significant bits. In this way, a compromise is obtained between precision (by the use of the thermometer-coded principle) and number of resistors or current sources (by the use of the binary-weighted principle). The full binary-weighted design means 0% segmentation, the full thermometer-coded design means 100% segmentation. Most DACs, shown earlier in this list, rely on a constant reference voltage to create their output value. Alternatively, a multiplying DAC takes a variable input voltage for their conversion. This puts additional design constraints on the bandwidth of the conversion circuit. |
#13
Posted 10 September 2014 - 11:18
E prea tehnic. Eram interesat de un rezumat pe intelesul tuturor despre avantajele si dezavantajele tehnologiilor folosite. Inainte de a deschide un topic caut pe google din principiu (de obicei ajung si pe la Wikipedia).
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#14
Posted 10 September 2014 - 13:32
E mișto. Întrebi în titlul topicului care tip de DAC e mai bun (de ex. ăla din Denon e delta-sigma, în Onkyo ai pulse-width modulator), apoi te dai lovit și te plângi că (citez)
Quote producatorii tot chestii de DAC picteaza pe mastile aparatelor, nimic despre analog sau că Quote producatorii nu se lauda niciodata cu etajul analogic din final, ci mereu cu titluri pompoase din zona digitala Ce vrei, de fapt, cu topicul ăsta ? |
#15
Posted 10 September 2014 - 14:23
Mai citeste odata ce am scris. Am fost explicit, nu pot decat sa-ti repet aceleasi lucruri. Uite, mai pe intelesul tau:
Care dintre tehnologiile de mai jos: - 20Bit Lambda Super Linear Converter - 1 Bit PWM/ACCUPULSE - M.A.S.H. Multi-stage Noise shaping - 27Bit Accumulating Digital Filter-Four Times Oversampling - AL24 Processing si altele existente (lista e deschisa), folosite in DAC-urile CD-playerelor, produce cea mai buna conversie din digital in analog, cat mai apropiata de realitate ? Acum ai priceput ? |
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#16
Posted 10 September 2014 - 16:35
"Cat mai aproape de realitate" e o chestiune extrem de subiectiva ce tine cont de set up-ul folosit , de urechile fiecaruia , de cultura in domeniul audio sau chiar de starea de moment( vorba cantecului: .."karma si feng shui-ul"...). Nu se poate defini si cuantifica asa ceva. De aceea nici nu se fac aprecieri e acest gen pe site-uri de specialitate sau de audiofilie. Tot la detalii tehnice sau la aprecieri gen " se aude cinelul mai natural" se ajunge.
Edited by edigee, 10 September 2014 - 16:35. |
#17
Posted 10 September 2014 - 16:44
Totusi, ma gandesc ca producatorii au incercat tot felul de idei in momentul cand au experimentat cu o solutie constructiva fata de celelalte.
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#18
Posted 10 September 2014 - 20:42
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