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DAC 8 High End D/A-Converter
Over the last few years we have exploited our long experience and profound knowledge of digital signal processing in the development of fully-featured disc and multi-source players. However, the DAC 8 is another device designed to operate purely as a converter, and achieves its fantastic performance through the use of the very finest technologies and uncompromising design. After protracted reflection we decided to go far beyond the aim of just building a sound card for the high-quality transfer of computer music, and our DAC 8 can accomplish so much more. In fundamental form it contains everything required to convert any form of digital source into analogue signals to the very highest standards. It is a complete high-end device of the most elevated quality, from the case right through to the mains power supplies.
The case is of all-aluminium construction: the base plate and top cover are machined from solid aluminium plates 6 mm thick, and we make the side and front panels from aluminium profiles which are extruded using special complex tools. The heavy case rests on vibration-damped absorber feet.
The seriousness of our claim that the DAC 8 is one of the world’s finest high-end converters can be judged by the fact that we employ two separate, sophisticated mains power supplies for the analogue and digital sections. A volume control is another unusual feature in a DAC, but it makes good sense if the user wishes to install active loudspeakers, or employ the DAC 8 as a pre-amplifier in conjunction with external power amplifiers. The volume control is of highly refined design, and exploits analogue control elements down to low volumes, as they avoid any loss of dynamic quality even at low listening levels. Two gold-contact relays are provided to by-pass the volume control, i.e. it can be removed entirely from the signal path when not required. A high-quality headphone output is also present.
The array of sockets on the back panel reflects the impressive facilities offered by the DAC 8: it features two high-quality analogue outputs, 1 x symmetrical (XLR) and 1 x asymmetrical (RCA), whose output resistance is very low at just 22 Ohms. This means that it is possible to drive active speakers for professional use, or with very long cables, without loss of quality. A slide-switch is used to determine whether the volume control is active or not. The CTRL socket below the mains socket is intended for updates and for external control of the DAC 8. Eight digital inputs are available: 4 x SP/DIF, 1 x optical (TOS-Link), 1 x BNC, 1 x AES/EBU, 1 x USB. All inputs support data rates of 32 kHz to 192 kHz at 16 ... 24-bit (TOS-Link 96/24). The USB input supports USB Audio Class 1 (USB Full Speed) at up to 96/24 and USB Audio Class 2 (USB High Speed) at a maximum of 192/24. For USB Audio Class 2 it is possible to select either synchronous or asynchronous transmission; a special driver is required for this.
One of the biggest problems in converting different digital sources is jitter (fluctuations in the transmission rate, or “clock”). The more pronounced the jitter, the worse the sound quality. That’s why T+A has invested tremendous effort right from the outset in developing measures to eliminate jitter, and for the DAC 8 we have taken a unique new approach. Jitter arises in the source device - especially in computers - and in the transfer of data between source and converter. For top-quality reproduction the jitter must be eleminated before the DAC converts the digital data into analogue signals. The jitter problem is a huge one, especially when computers are involved, as these machines were never designed with high audio quality in mind. Our investigations have shown that the “jitterbugs” used by many high-quality DACs to reduce jitter are not sufficient on their own, so we have developed a unique and even more sophisticated system for clock generation: in the first stage the received data are processed and decoded. At this early stage a raw clock is derived from the received data stream, and a PLL circuit is used in an initial cleaning stage to remove coarse jitter from the source device and the transfer path. This clock is now analysed very closely by the DAC 8’s micro-processor: if it fulfils certain minimum criteria in terms of frequency and stability, the DAC 8’s D/A converters are switched to an extremely accurate master-clock generated internally in the DAC 8, with extremely low phase noise. This clock is completely de-coupled from the source device, and therefore eliminates all trace of jitter interference from the source and the transfer. For the purpose of generating the local master-clock the DAC 8 is equipped with two separate quartz oscillators which are extremely accurately matched - one for the clock families 44.1 / 88.2 / 176.4 kHz and one for 48 / 96 / 192 kHz. This sophistication ensures that perfect converter clocks are available for all clock frequencies from 44.1 kHz upwards. If the incoming signal does not fulfil the requirements for switching to the local clock oscillators, a second PLL stage (2nd jitterbug) is employed instead of the quartz oscillators. The greatly improves the result from the first jitterbug stage, and reduces the residual jitter remaining after the first stage by a factor of 4.
The core of the DAC 8 is the converter. As in our high-end players this device also employs the superior quadruple arrangement with eight 32-bit converters from Burr-Brown in a double symmetrical circuit. This circuit provides perfect compensation for non-linearities, and the residual background noise - which is excellent in any case with the 32-bit converters we employ - is reduced by approximately a further 6 dB. The result is a dynamic performance which is hardly capable of improvement, with a perfect “black level”, extreme linearity and freedom from distortion, even in critical passages and the most minute musical details. Oversampling is carried out by a modern 56-bit signal processor, for which T+A has developed algorithms specific to our equipment, offering perfect timing characteristics. They are based on Bezier polynomials: Bezier interpolation and Bezier / IIR combination. A standard FIR filter and a short FIR filter are also provided. These options make it possible to select the optimum sound quality to suit the individual piece of music. The DAC 8 can even invert the absolute phase of the audio signal at the digital level, and thereby correct material recorded with incorrect absolute phase.
Ten long years ago we developed a means of galvanically separating the converter from the analogue section for use in our high-end players: this provides complete galvanic isolation of the digital section from the analogue section using magnetic “i-couplers” made by Analog Devices. The result is to prevent any interference from the source devices finding its way into the analogue section. Computers, in particular, generate enormous levels of interference which would ruin the superior sound qualities of the audiophile output stage without this measure. The “State of the Art” analogue stages are of fully discrete and symmetrical construction, and do not employ OP-AMPs. Their linearity is not a function of “hard” negative feedback, as is typical of OP-AMPS, but rather od the quality of the circuit design and the components employed, which are selected and matched to very fine tolerances. A further unique feature of the DAC 8 is its switchable analogue bandwidth, which has already proved so effective in our high-end players. The limit frequency of the DAC 8’s analogue reconstruction filter can be switched between 60 kHz and 120 kHz; the “ultra-wide” 120 kHz setting is the key to perfect frequency response and phase characteristics when used with power amplifiers with a broad-band output - such as those in the T+A range, naturally. The phase linearity and signal fidelity of the “ultra-wide” circuit also has a perceptible effect in the audible range, and allows an open sound image with phenomenally clear positioning and ultra-lively dynamics.
Specifications
D/A converter:32-Bit, 384 kHz Sigma Delta, 8-times oversampling, double-mono-quadruple
Analogue filter:3rd order phase linear Besselfilter, switchable 60 kHz or 120 kHz
Frequency response:2 Hz - 20 / 22 kHz (44.1 / 48.0 kSps)
2 Hz - 40 kHz (88.2 / 96.0 kSps)
2 Hz - 80 kHz (176.4 / 192.0 kSps)
Total harmonic distortion:< 0,001 %
Signal noise (A):116 dB
Channel separation:110 dB
Analogue outputs:coaxial (Cinch)2,5 Veff / 22 Ohm fixed. 0 ... 2,5 Veff variable
Symetrical (XLR):5,0 Veff / 22 Ohm fixed. 0 ... 5,0 Veff variable
Digital output:1 x coax, IEC 60958 (CDDA/LPCM)
Digital inputs: SP/DIF (16 - 24 Bit):4 x co-ax, 1 x BNC, 1 x AES/EBU up to 192/24, 1 x TOS-Link up to 96/24
1 x USB with USB Audio Class 1 (USB full Speed) up to 96/24, adaptive mode and USB Audio Class 2 (USB high Speed) up to 192/24 asynchronous mode*
Accessories:F8 remote control handset included, asynchronous drivers for Windows XP, Windows 7 and MAC OS
Mains connection:Wide-band mains section, 100 - 240 V, 50 - 60 Hz
Dimensions (H x B x T):9,5 x 27 x 27 cm
Weight:6 kg
Ausführungen:Case black aluminium 42, cover silver aluminium 43
* Driver for Windows XP, Windows 7 and MAC OS free of charge on T+A website for download. A suitable media player is necessary.
以下中文解说: 转自My-Hiend.com
T+A开发与制造最高品质的数位与类比装置上已经有超过二十年以上的经验。我们很早以前就已经决定要致力于数位信号处理，因为我们知道要将数位音乐以自然纯粹的方式重现，关键就在于将数位数据转换成类比数据的品质。我们在九零年代中导入了PreDA 3000 AC：这是一台性能绝佳、独一无二的前置放大器/DAC。我们的高端碟片播放机在那时也是无可匹敌的领导者，究其主要原因就是它们具有精密的D/A 转换器，而且经由出色的类比输出平台产生的自然音色也一直都是重要的特色。
在过去的几年当中，我们利用丰富的数位信号处理经验与知识来开发全功能碟片与多源播放机。然而，DAC 8 是另外一个纯粹设计来当做转换器操作的装置，并且透过使用最好的技术与强势设计达成其绝佳的表现。在延长的反射后，我们决定不再只将目标局限于建立电脑音乐高音质转换音效卡上，而且我们的DAC 8 可以有更大的成就。它的基本格式包含了将任何型式的数位源流转换成最高标准类比信号所需的所有条件。这是一台全面高端装置，从外壳到主电源供应都是最高级的。
铝合金外壳：底板与上盖是由6 mm 厚的实心铝合金板加工制成，侧板与前面板是使用特殊复合工具挤压成型的铝合金外形。厚重的外壳安装在避震缓冲脚上。从我们在类比与数位部件采用了两套独立、精密的主电源供应器，就可以判定我们为什么会认真的宣称DAC 8 是世界上最高端的转换器之一了。
DAC 上另外一个与众不同的特点就是音量控制，如果用户希望安装主动音箱或是将DAC 8 当作前置放大器来外接功率放大器，这个特点就很有用处。这个音量控制设计非常精细，并且在低音上使用类比控制元件，因为即使在低聆听水平也可以避免动态质量的损失。两个金触点继电器用来旁通音量控制，也就是说如果不需要使用的话，可以将它们从信号路径完全移除。此装置还配备了一个高级耳机输出。
背板上的插槽也是DAC 8 引人注目的设施：包括两个高级类比输出、一个对称输出(XLR)以及一个不对称输出(RCA)，它的输出阻抗非常的低，只有22 Ohms。这意味着可以在专业使用中用它来驱动主动式喇叭，或是使用非常长的线材也不会降低音质。使用滑动开关来决定是否启动音量控制。电源下方的CTRL 插槽是用来更新以及外部控制DAC 8 用的。具有八个数位输入：4 x SP/DIF、1 x 光学(TOS-Link)、1 x BNC、1 x AES/EBU、1 x USB。所有输入都支援16…24 位元(TOS-Link 96/24) 32kHz 到192 kHz 的数据传输率。USB 输入最高支援到96/24 的USB Audio Class 1 (USB 全速)以及最大192/24 的USB Audio Class 2 (USB 高速)。USB Audio Class 2 可以选择同步传输或是异步传输；这需要一个特殊驱动程式才能达成。
在转换不同数位源流上所遭遇的最大的问题之一就是时基误差(传输速率的时基误差，或是“时脉”)。时基误差愈显著音质就愈差。所以T+A 一开始就投注大量的心力来开发消除时基误差的方法，而在DAC 8 上我们就采用了一个独特的新方法。时基误差是产生于音源装置 – 特别是在电脑上–以及音源与转换器之间的数据传输。为了呈现顶级的重现，必须在DAC 将数位数据转换成类比讯号之前就将时基误差消除。时基误差是一个大问题，尤其是牵涉到电脑时，因为这些机器在设计时从来不将高音质列入考虑。我们发现许多高级DAC 用来减少时基误差的“时基误差干扰器”效果并不好，所以我们开发了一个独特而且更加精密的系统来产生时脉：在第一阶段将接收到的数据处理与解码。在这最初的阶段，从接受到的数据流中会产生一个原始时脉，而且在初始清除阶段使用了PLL回路来移除从音源装置与传输路径产生的原生时基误差。现在这个时脉由DAC 8 的微处理器进行非常精密的分析：如果在频率与稳定度上符合了某些最低标准，DAC 8 的D/A 转换器就会切换到由DAC 8 所产生的精准主时脉，而且相位杂讯极低。这个时脉从音源装置就完全解耦，所以能够将从音源与传输产生的时基误差干扰痕迹完全消除。为了能够产生局部的主时脉，DAC 8 配备了两个精准搭配的独立石英震荡器 - 其中一个的时脉是44.1 / 88.2 / 176.4 kHz，另一个是48 / 96 / 192 kHz。这样的精巧化确保完美的转换器时脉适用于44.1 kHz 以上的所有时脉频率。若是进来的信号无法满足切换到局部时脉震荡器的要求，就会采用第二个PLL (第二个时基误差干扰器)阶段来代替。这样的方式大大的改善了第一时基误差干扰器阶段的结果，并且减少第一阶段后剩下的残余时基误差达四倍。
DAC 8 的核心就是转换器。在我们的高端播放器中，此装置也采用了八个Burr-Brown 的双对称回路32 位元转换器的高级四重安排。此回路可以提供完美的非线性补偿，同时残余背景杂讯也大约更进一步的降低6dB，这在所有我们采用的32位元转换器上都是卓越的。这样的结果就是产生几近完美的动态表现，具有完美的“黑电平”，极度线性而且不失真，即使是在临界通道与最微小的音乐细节也可完美呈现。超取样是由一个新式的56位元信号处理器来执行，这是T+A特别针对我们的设备开发出的算法，可以提供完美的校准特性。它们是以贝兹多项式为基础：贝兹插值与贝兹/IIR组合。也提供了标准FIR 滤波器与短FIR 滤波器。这些选项让选择最佳的音质来配合个别的乐曲成为一种可能。
DAC 8 甚至可以转换数位水平上的音讯的绝对相位，从而改正以不正确绝对相位录制起来的内容。早在十年前我们就开发了一种将转换器从我们的高端播放机上使用的类比部件流电分离的方法：这个方法利用Analog Devices 制造的电磁耦合器将数位部件从类比部件完全流电分离。如此可以防止音源装置的干扰侵入类比部件。没有采用这种方法的电脑尤其会产生大量的干扰，进而破坏音乐爱好者输出平台的优异音质。最先进的类比平台是完全分离与对称的结构，而且不会采用OP-AMPs。它们的线性不是用来做为像是典型的OP-AMPS 这种 “硬式” 负回馈的功能，而是强化回路设计以及精选采用组件的品质。DAC 8 另一个特点就是可切换类比频宽，这在我们的高端播放机上已经是被证明为非常有效的。DAC 8 的类比重建滤波器的有线频率可以在60 kHz 与120 kHz 之间切换；当与具有宽频输出(例如T+A 系列)的功率放大器一起使用时，120 kHz 超宽频率设定自然是完美频率响应与相位特性的关键。“超宽”回路的相位线性与信号逼真度在可听见的范围内也具有可感知的效果，而且也可以提供有清楚配置与非常生动的开放声音影像。
目前看到的售价是1,890欧元或2,900美金.
似乎是另一个期待品, 等我这里引进再去试试看  |
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发表于 2012-6-26 16:44:40
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