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发表于 2009-5-9 22:13
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接下来翻译一篇Ｌｉｎｎ网站上“洗脑”用的文章
Why the Klimax DS is the best way to play CDs
* 1 Design Philosophy
* 2 Reading the data from the disk
* 3 Converting the data to audio
o 3.1 Noise sources
o 3.2 Jitter
o 3.3 Up-sampling and Quality of the DAC chip
o 3.4 Topology of circuit
为什么Ｋｌｉｍａｘ ＤＳ是播放ＣＤ最好的方式？
* 1 设计哲学
* 2 从盘片读取数据
* 3 把数据转化为音频
o 3.1 噪音来源
o 3.2 抖动（Jitter）
o 3.3 升频和ＤＡＣ芯片的质量
o 3.4 拓扑电路
Design Philosophy
Where does a company like Linn Products add value in a digital audio source product? It is not in the reading of ones and zeroes from the disk – there are many cheap, mass produced products that can serve this function very well.
Where Linn Products excels is in producing the best possible audio from the digital data. This is the one and only goal of the DS product range; this apparent limitation in reality means that the products are highly focused and deliver an unprecedented level of audio performance. The Linn DS products have been developed without any of the compromises that are inevitable in more ‘integrated’ products.
The function of a CD playback can be split into two basic elements
1. Reading the data from the disk
2. Converting the data to audio
设计哲学
莲在音源器材里是怎样提升产品的内在价值的呢？音源，绝对不是从盘片上读取１和０那么简单，当然有很多的公司大量生产廉价的产品，的确可以读１和０。 但是莲的出类拔萃就在于从数码数据中做出最好的声音来。 这就是ＤＳ系列产品唯一的目标，我们就是要做出声音能达到新高水准的产品。 和各种各样的”集成“产品相比，ＤＳ是在声音上毫不妥协的产品。
Reading the data from the disk
The data on the disk is digital. Therefore the retrieval process can be perfect (considering that when you load software from a data CD it would not work if there were errors). In a traditional CD player the data is read at the same time as the audio is being reproduced. There is no technical benefit in this time linkage; indeed it has the disadvantage that if a read error occurs there is no time to attempt a re-read.
When a CD player encounters corrupt data it will attempt to mask the problem by extrapolating the good data, when a CD is ripped to computer disk there is a clever system of re-reading of difficult sections of the disk to ensure no corrupt data is stored to hard disk (this is why some CDs take a lot longer to rip).
In the Linn DS system the data is read to computer memory (hard-drive), this process can be verified as error-free by the use of checksums.
The transfer of data from the hard-drive to the Linn DS is over Ethernet using TCP-IP. This protocol ensures the integrity of the data delivered to the DACs.
Extensive end-to-end testing has verified that the data at the Klimax DS is precisely the same data as on the original CD.
从盘片读取数据
盘片上的数据是”数码”的。 所以数据的读取过程应该可以做到完美。（想一下，如果你从光盘上读取一个软件，如果有错误的话，软件是根本无法运行的） 对于传统的ＣＤ唱机来说，数据的读取 和 音频的产生 是同时进行的。 其实，同时做这两件事在技术上是没有好处的； 实际上，这样做有个很大的缺点：当你传统ＣＤ唱机读取到错误数据的时候，是没有时间来重新读取的。当一部ＣＤ唱机碰到没法读准的数据的时候，它会“猜测”出一个好数据来；而当一场ＣＤ唱片被ｒｉｐ到电脑里去的时候，电脑的软件系统可以智能地重读数据，让最终硬盘里存储的数据都是正确的。（这也就是为什么你在ｒｉｐ唱片的时候，有些唱片要花更长的时间才能被ｒｉｐ下来）
在莲ＤＳ系统里，数据是被事先读取到电脑记忆体（硬盘）里的，这个过程是可以被验证的，经过了校验，就能保证最后的数据没有错误。数据从硬盘到莲ＤＳ是通过网线传输的，符合ＴＣＯ－ＩＰ规范。这种结构能保证数据传输的完整性。经过了大量的点到点的试验，我们可以确信能达到Ｋｌｉｍａｘ ＤＳ的数据和ＣＤ光盘原来的数据是一样的。
Converting the data to audio
Having ensured that the data is correct, the element that governs the quality of the audio is the digital to analog converter (DAC). There are a number of factors that influence the DAC performance:
* Noise sources
* Jitter
* Up-sampling and Quality of the DAC chip
* Topology of circuit
把数据转化成音频
取保了数据的准确之后，另一个对最终音质起重大作用的因素就是ＤＡＣ了。 有几个因素会影响ＤＡＣ的表现：
噪音来源 ； 抖动（Jitter） ； 升频和ＤＡＣ芯片的质量； 拓扑电路
Noise sources
In a CD player there are inevitably moving parts. Even the highest quality CD mechanism produces noise, not just acoustic noise but electrical and magnetic noise.
In the listening room the acoustic noise is apparent to the user; however it is the electrical and magnetic noise that can be having a detrimental effect on the DAC circuit which may be the more significant element.
It is worth noting that this problem also exists for similar products with integral hard disk drives.
In the DS products this noise source is absent.
噪音来源
在ＣＤ唱机里，肯定会有移动的组建。哪怕最高质量的ＣＤ转盘也会产生噪音，不光是我们耳朵听到的噪音，还会产生电子噪音和电磁噪音。
在听音室里，转盘移动的噪音是耳朵可以听见的。但是电子噪音和电磁噪音这些难以察觉的噪音会对最终的音质产生明显的负面效果。
如果一台音频播放器里放进了一个硬盘的话，噪音的问题依旧没有办法解决。－ 在ＤＳ里 是没有噪音来源的。
Jitter（抖动）
Klimax DS has a similar clock architecture to Linn’s CD players. The audio clock is generated by an ultra low jitter oscillator located close to the DAC chips. This clock is used for the DACs and also provides the master timing reference to the entire digital path.
It is worth noting that this architecture where the data is ‘pulled’ from the network using the clock at the DAC is inherently better than systems where the data is transported by SPDIF or USB links, where the DAC has to ‘lock’ its clock to that at the sending end.
Jitter（抖动）
Ｋｌｉｍａｘ ＤＳ和之前莲的ＣＤ唱机有类似时钟结构。时钟是由一个超低Ｊｉｔｔｅｒ的振荡器控制的，这个振荡器的位置就在ＤＡＣ芯片边上。这个时钟不但为ＤＡＣ服务，也控制整个数据系统。
这里值得注意的是： 从网络里“拉”数据出来的这种结构里，天生的就比用SPDIF或USB能获得更好的时钟控制。在SPDIF或USB系统里，ＤＡＣ必须“锁定”数据的发出端。
Up-sampling and Quality of the DAC chip
At Linn Products there is an on-going research project in which DAC chips are evaluated. For each candidate DAC chip a custom evaluation board is developed. These are subject to a suite of objective tests that we have developed for DAC assessment. The final arbitration for all these trial systems is the listening test.
On the basis of this research the Wolfson WM8741 has been selected for the Klimax DS.
In the Linn DS products we are using a custom up-sampling system that has been developed as a part of Linn’s DAC evaluation project. There are three advantages to this approach:
1. Choice of custom filter shape – again extensive listening tests were used.
2. We have far greater processing power available for up-sampling within an FPGA than is available from the built-in up-samplers in the DAC chips.
3. Electrical noise from the up-sampling process is located in the digital circuit (not in the sensitive analog part).
For more details on this subject you can read the Up-Sampling article. http://docs.linn.co.uk/wiki/index.php/Up-sampling
升频和ＤＡＣ芯片的质量
我们有一项不断进行的研究工作，就是评估市场上各种ＤＡＣ芯片的质量，来选择好的ＤＡＣ来生产我们的音源。 对于每种ＤＡＣ，我们发展出了一种有针对性的评估方法。我们有多种ＤＡＣ评估项目，每种项目都有不同的侧重点。最终的评估只有靠耳朵！ 经过这样的研究，我们选用了 Wolfson WM8741 作为 Ｋｌｉｍａｘ ＤＳ 的 ＤＡＣ 芯片。
另外，针对各种不同的ＤＡＣ芯片，我们还量身定制了不同的升频方案。 这样做有三个好处：
－评估并选择特定的过滤波形（同样 最终的评估只有靠耳朵！）
－我们有强大的升频方法编写能力，比ＤＡＣ自带的升频方案要好得多。
－升频过程产生的 电子噪音 被控制在了 数码电路里 （敏感的模拟电路不会受到干扰）
如果您对升频这个话题想知道更多， 请看这里 http://docs.linn.co.uk/wiki/index.php/Up-sampling
Topology of circuit
The design and layout of the DAC circuit has a considerable impact on its performance. An area where the Klimax DS improves on previous Linn designs is the reduction of ground currents. This area is often overlooked by engineers who assume zero impedance ground. In reality there is always some resistance and inductance in all ground connections. It follows that any ground current (such as return current from digital signals) will inevitably cause a noise potential.
This is particularly damaging if the noise source is coherent with the audio signal – as is the case with the serial audio data signal.
拓扑电路
ＤＡＣ相关电路的设计对其最终表现有重要影响。 相对于我们之前的产品，Ｋｌｉｍａｘ ＤＳ在控制 接地电流 方面取得了进步。 这个方面常常被别的厂家忽视，他们会假定 接地阻抗 为零。 其实在在接地连接里，总是有一些电阻和电感的。 所以任何接地电流（比如数字信号的返回电流）都将最终成为潜在的噪音源。
如果这种噪音源和音频信号是联通的话，会特别不利于音质。 对于连贯的音频数据信号，也是同样道理。
（因为小弟不懂电子 肯应有翻译的错误 特别是最后一段 请大家指正）
[ 本帖最后由 wbjia 于 2009-5-9 22:14 编辑 ] |
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