现在很多发烧友采用电脑USB输出 - DAC解码器的方式作为音源。在这个架构下，来自电脑USB口的数据，往往受到电脑噪音、电磁辐射等的干扰而显得比较“脏”。本身来自电脑的音频数据流，其时钟精度也不可能高，实际往往jitter很高，对于接收端的解码器来说，在很大程度限制了其表现，换言之哪怕你用了顶级的解码器，也会受限于来自电脑的USB音频流的质量，而最终出来的声音平平。

在这个情况下，要提升“电脑 - 解码器”这个音源组合的素质，有两个办法，一是使用结构干净、功能单一、USB输出质量较高的“专机”或者专用数播（比如Aries、Aurender），另外一个就是给普通电脑加一个所谓“USB净化器”。前者暂且不说，一般也代价不菲，后者的好处是通过一个并不贵的净化装置，提升电脑USB输出数据的质量。

我之前介绍过的国内设计制造的“泰坦鸟”和逸恒“魔方”就是此类小玩具，他们原理不同，但起的作用类似，都是过滤、重整USB信号，给解码器提供质量更好的USB audio stream，实际得到的音质提高也是非常明显可闻的。记得我第一次听的此类设备是逸恒“魔方”，当时对声音的改善觉得非常惊讶，兴奋地直接写了一个长贴，称之为改变了自己观念的、有启示性的玩具。得到的启示是：原来通过对USB信号进行净化，可以得到如此明显的音质提高。

国外也有几种起到这种作用的USB净化器，其中我玩过觉得很不错的、价格不贵而值得推荐的是美国Wyred4Sound（一般简称W4S）出品的Recovery。这个小玩意美国售价199美金，国内1799元人民币，美国制造（W4S的产品全部在美国制造），包装内还原配了一个9V直流输出的稳压电源。使用非常方便，就是把它接在电脑和解码器之间——电脑USB接到Recovery，然后Recovery再USB输出到解码器。无需驱动，只要多用一根USB线，就完成了USB净化的作用。来自电脑的USB数据流，进入Recovery之后经过它内部Femto高精度时钟的优化之后，输出高质量的USB音频流到解码器。主要是两个作用：1、消除来自电脑的噪声，2、利用Recovery的Femto Clock提高音频流的时钟精度。

https://www.audiostream.com/images/styles/600_wide/public/7516recovery.jpg?itok=6p9lqTdQ

下图是简单的接口和使用示意图示意图。两个指示灯，上面灯亮表示接收到信号，下面灯亮表示是USB2.0（不亮表示USB1.0）。

https://www.audiostream.com/images/7516recovery2.jpg

The Sound of the Recovery USB Reclocker

Using the power supply and the 6-inch USB cable provided by Wyred 4 Sound, I experienced a definite improvement to the sound I was hearing from the MSB Technology Analog DAC. The bass and the mid bass were better defined with the Recovery and more dynamic sounding. The midrange’s focus was sharper and appeared to move slightly forward in the soundstage compared to the sound with no Recovery. I felt that the highs had better definition that was probably helped by a perceived reduced noise floor. The soundstage appeared wider with the use of the Recovery providing a lager sonic presence to the sound. I was unable to find any negatives to attribute to the contribution the Recovery made to my Analog DAC; it just improved what I was hearing.

使用原配的USB接线和电源，我把Recovery用于MSB Analog解码器，听到了明确的声音提升。低频和低频上段层次和解析更好，也更为动感。中频的聚焦更锐利，和不用Recovery时相比也更为凸现。高频解析提高，整体声音的底噪明显降低。使用之后声场也会变大，造成更真实可信的临场感。对于我的听音系统来说，我找不出什么负面的影响，听起来就是全面性的提升。

Comparisons

I decided to base the comparisons of different USB enhancement devices with the supplied cables / connectors, and power supplies that come with each product.

The iFi Audio micro-iUSB3.0
As reported in my review of the micro-iUSB3.0, the sound using the supplied USB 3.0 cable and iPower power supply was warm with a full mid bass. The Recovery USB Reclocker has the larger soundstage and a more balanced tonality that was relatively neutral compared to the micro-iUSB3.0.

The Uptone Audio USB REGEN
Using the solid connector and the supplied power supply, I found the USB REGEN to have a lighter sound with less bass than the Recovery USB Reclocker. There is a great sense of clarity to the sound of the USB REGEN, but again, the Recovery USB Reclocker sounded to my ear to be better balanced and more neutral.

The Intona Technology USB 2.0 High-Speed Isolator
The Intona USB 2.0 High-Speed Isolator (Industrial Version) had a similar overall tonal balance compared to the Recovery USB Reclocker, but was slightly darker sounding. The Intona had a smaller soundstage in both width and depth compared to the Recovery. I did find the Recovery to be a little more detailed with a slightly forward midrange perspective compared to the Intona.

和其他3个同类产品的对比

1）iFi micro-iUSB3.0用原配的线和电源时，声音温暖，中低频丰满。Recovery声场要更大一点，音色更平衡，比起iFi来更为中性。

2）Uptone Audio USB REGEN使用原配的接头和电源，听起来低频略少，清晰度非常好，但Recovery在我听起来更为平衡和中性。

3）Intona和Recovery的整体音色平衡非常相似，但Intona听感略暗，声舞台也较小一点，宽度和深度都是如此。我觉得Recovery的解析略高，中频稍微更前突一点。

Comparison Conclusions
I guess if I could only have one of these USB enhancement devices, I would select the Recovery USB Reclocker as it sounded the most neutral with the largest soundstage. But as one begins to change cables and power supplies, my top choice rankings change. For example, the iFi Audio micro-iUSB3.0 being fed with a Wireworld USB 3.0 cable, outperforms the Recovery, but at a significantly greater cost.

假如我只能用一个USB净化设备，我就会选择Recovery，因为它听起来声音最为中性，声舞台最大。假如换线、换电源，那么结论会有所变化，比如给iFi Audoi micro-iUSB3.0换为线世界的USB3.0线，可以表现更好，但是付出的代价就远远超过Recovery了。

Conclusion
At $199.00, the Wyred 4 Sound Recovery USB Reclocker offers excellent performance at a very reasonable price. One can boost the performance of the Recovery USB Reclocker by using a different USB cable from the device and a linear power supply like the HDPlex. However, I could be very happy just using the Recovery as supplied by Wyred 4 Sound and forget the many possible modifications.

总结：在199美金这样一个价格，Recovery这个产品提供了非常出色的表现，性价比很好。通过换USB线、换更好的线性电源，可以获得进一步提高，但是就用它原配的电源我已经觉得很开心了，可以忘却那些“升级方式”。

下面是我玩Recovery的时候拍的开箱照。层次更清晰、声底更干净和透明，是很容易察觉到的Recovery给系统带来的好处。特别是对普通的笔记本电脑来说，提升可以说非常显著。 

另外，6moons网站的主笔Srajan Ebaens先生对Recovery的评测也是值得一看的，原文链接：http://6moons.com/audioreviews2/wyred3/1.html  他的试听和描述是：在一套不到2000欧元的系统上，改进非常明显，在一套一万多欧元的高级系统上，改善程度减少但仍可听出。改善的具体描述关键字：fleshier fuller textures（更丰满的织体），Calmness（我们这里部分老烧喜欢说的“安定感”）。It eliminated some embedded 'tizz' or treble dither（高频的硬边和失真消除）。The silence between tracks was no more silent than before（背景更漆黑）。

最后给一张Recovery的内部图。线路板的中央部位就是厂家号称达到飞秒精度级别的高级晶振Crystek CCHD-575 series ultra-low phase noise oscillator。 

http://6moons.com/audioreviews2/wyred3/5.jpg

（完）