发烧神话一大把，自己一个一个试过来.. - 第2页

lighting · Oct 26th, 2012, 21:57

引用:

作者: hugoo

实在无聊了，在看这个54页806个帖子，关于发烧USB线的..吵呀吵，没完没了..

..

我倒是觉着，用USB 作为Audio Data的传输，最大的瓶颈是在USB 口的优先权很低，如果计算机在多任务的情形下，很可能数据流截断，那可不仅是声音失真了。

作为USB cable，只要你别买到假冒线（比如淘宝上买的，一元店买的），别在正吸尘的吸尘器边上使用，不会成为问题。

好像发烧友都有点洁癖，总觉着看不见的细菌沾满了他的已经非常干净衣物！

dalplex · Oct 26th, 2012, 23:08

银彩那个HDMI的演示我是听过的。我完全听不出任何区别。最后实在没什么好吹的，解释成每根线都是手工焊的。

busrel · Oct 26th, 2012, 23:50

引用:

作者: sgyyz

Data streaming in USB isosynchronous mode (which is implemented in USB DAC) is susceptible digital data loss, as opposed to block mode transfer. How c...

如果是isosynchronous mode那么data loss是不能恢复的，因为这个模式不提供error correction,当然有一位bit提供crc校验，但是最多只能检测出这个包不能用罢也。这个模式甚至不提供包裹重新发送。

不过一个破usb线要卖到$120简直是抢钱。其实最简单的办法就是用粗铜导线完事了，减少传输错误其实很简单，而且即使ebay上买来的破usb先在isosynchronous模式下应该错包率也小于千分之一吧（猜得），所以这$120玩意就是人傻，钱多，速来。

我亲自听过故意传输错误路高的音乐，高音部分会出现奇怪的噪音，较低的音则基本不被影响，估计着是掉包部分对高频数字信号影响大，毕竟频率高掉一个包就变频了，呵呵。

其实上述这些都是废话，听音乐用hdmi传输声音最好了，错包自动重发，所以哪怕是ebay $1买来的hdmi线，也和futureshop砍人出血的$100的monster 线无区别。

sgyyz · Oct 27th, 2012, 10:23

引用:

作者: busrel

如果是isosynchronous mode那么data loss是不能恢复的，因为这个模式不提供error correction,当然有一位bit提供crc校验，但是最多只能检测出这个包不能用罢也。这个模式甚至不提供包裹重新发送。

不过一个破usb线要卖到$120简直是抢钱。其实最简单的办...

没认真去研究过。但以前看过的文章都是isosync streaming 。如果说没有error correction ，那错误一定会有，只是到了什么程度。

数码的，都可以响出来很干净的音质。至于喜不喜欢，完全是个人听感。很多人都会说是bullshit ，但这种听感不同的情况是存在的。完全是个人选择。

如果完全不讲究，其实什么都可以听。没必要长篇大论。

Sent from my SGH-I747M using Tapatalk 2

hugoo · Oct 27th, 2012, 12:32

网上看来的。。‘’USB线听感不同的可能的技术原因。

-1- Waveform distortion: due to its physical properties, the cable can possibly affect the square waves, in interaction with the source and receiver (from that point of view they form an analog system). This in turns affect the accuracy of the recovered system clock fed to the DAC chip. This in turns affects the accuracy of the digital to analog conversion.
-2- Interaction in between power supply lines and data lines: it has been measured that 1Khz spikes coming from the data lines can couple into the power supply lines and that the longer the cable, the stronger the effect. Such spikes could maybe be directly heard as noise depending on the dac's pcb layout. Such spikes could also affect the accuracy of the ICs inside the dac, resulting either in increased jitter (for the clock or the receiver chip) or directly in higher distortion (for the dac chip and the opamps of the analog section).
-3- Rfi shielding: the usb cables are quite susceptible to high frequency noise pick-up (a reason among others why long runs cannot be used). Noise making its way into data line can perturbate the receiver chip, causing early/late triggers, resulting once again in a poorer system clock. If the noise couples into the power supply lines, see -2-.
-4- HF noise attenuation: the source computer signal's quality can vary widely. HF noise can find its way on the various USB lines. A cable attenuating this HF noise could thus have an impact. It could however interacts with -1-.

All these are sound engineering reasons and have been measured or could be, given time and the proper (read expensive) equipment. The fact that USB cables affect the analog output of the DAC seems to have been proven by measurements by Paul Miller for the january issue of Hifi News (if anyone has the article, I'd love to read more than hearsay).

HOWEVER, the existence of a technical difference in between cables does NOT prove the existence of anaudible difference. It is even more so as the differences outlined above are fairly small and that cables manufacturers don't seem to bother measuring the actual differences their cables make. And you have to keep in mind before any generalization that USB audio uses 3 different protocols with various levels of weakness to those problems, that the USB receiver chips are very different and that DACs are coming from a bazillion different manufacturers who pay more or less attention to their designs.

Sent from my GT-I9100M using Tapatalk 2

hugoo · Oct 27th, 2012, 12:51

引用:

作者: sgyyz

没认真去研究过。但以前看过的文章都是isosync streaming 。如果说没有error correction ，那错误一定会有，只是到了什么程度。

数码的，都可以响出来很干净的音质。至于喜不喜欢，完全是个人听感。很多人都会说是bullshit ，但这种听感不同的情况是存在的。完全是个人选择...

你diy的bottlehead咋样了?

我换了BNC感觉其实很不错的，可是没法跟以前的比较所以不敢妄言，唉，就是几块钱的事，至少数码传输部分都是符合标准的75ohm的啦。

Sent from my GT-I9100M using Tapatalk 2

lighting · Oct 27th, 2012, 13:53

引用:

作者: hugoo

网上看来的。。‘’USB线听感不同的可能的技术原因。

-1- Waveform distortion: due to its physical properties, the cable can possibly affect the square waves, in interaction wi...

这些是数字信号固有的缺陷，不仅仅是 for audio data.

我觉着‘’USB线听感不同的可能的原因。”，最大嫌疑是听感可以“thought”，而人类的听觉又不怎么样，但烧友又怕别人说自己木耳，就纷纷附和“神耳”的听感！

说一个现象，就可以说明，同样的HDMI 的视频数字传输，怎么没有那么大的争议？

说起来视频的数字传输比音频传输的频宽，抗干扰能力要求强许多，大家为什么都对3刀的HDMI 没有争议？反而对音频数字传输有争议？

hugoo · Oct 27th, 2012, 14:19

引用:

作者: lighting

这些是数字信号固有的缺陷，不仅仅是 for audio data.

我觉着‘’USB线听感不同的可能的原因。”，最大嫌疑是听感可以“thought”，而人类的听觉又不怎么样，但烧友又怕别人说自己木耳，就纷纷附和“神耳”的听感！

说一个现象，就可以说明，同样的HDMI 的视...

谁说没有发烧hdmi线

2米要卖110$。

http://www.shop.perfecthometheater.c...CABLE-HDMI.htm

Sent from my GT-I9100M using Tapatalk 2

hugoo · Oct 27th, 2012, 14:52

引用:

作者: lighting

这些是数字信号固有的缺陷，不仅仅是 for audio data.

我觉着‘’USB线听感不同的可能的原因。”，最大嫌疑是听感可以“thought”，而人类的听觉又不怎么样，但烧友又怕别人说自己木耳，就纷纷附和“神耳”的听感！

我不怕，听不出就是听不出嘛。
这个usb跟spdif还是不同，spidf要求75ohm, usb就没听说有这个要求，到底里面怎么work的还是搞不清楚。

不过数字信号传输绝不像外行想的那么简单吧，传输媒介哪里知道什么0和1，实质还是模拟信号在线里面传的。

Sent from my GT-I9100M using Tapatalk 2

lighting · Oct 27th, 2012, 17:19

引用:

作者: hugoo

谁说没有发烧hdmi线

2米要卖110$。

..

这么说吧，大家的台式电脑，天天在用，有谁非常得纠结 DVI 线的价位，抗干扰性，粗细，里面的芯是铜的还是银的？

没有吧！为什么？因为图像很清楚啊，没有什么不好，没人要想到买100刀的DVI 线，以达到更清楚的效果，因为大家知道，就这样了，不可能更清楚了。

HDMI 线就是DVI 线里的一部分，两者可以用个简单的转接头互换。

那简单得多，要求也低很多的数字音频 USB 传输线，为什么反而会有那么大的争议？？？

busrel · Oct 28th, 2012, 00:42

引用:

作者: hugoo

网上看来的。。‘’USB线听感不同的可能的技术原因。

-1- Waveform distortion: due to its physical properties, the cable can possibly affect the square waves, in interaction wi...

这些其实说的都不对。CRC校验会把错包扔掉的，不会affect sound，最多是缺那个包而已。如果有任何inteference不管是线还是发送或者接收端都会造成crc校验错误的，写这些文章的人可能计算机知识都没学好，crc校验可能是1bit，甚至是3bit的，校验准确率为 100%- （2^8^3）^(-1).

就像我说的，如果有crc校验+错包重新发送，那么错码率基本就可以认定为0了，比如hdmi就是。

hugoo · Oct 28th, 2012, 10:11

引用:

作者: busrel

这些其实说的都不对。CRC校验会把错包扔掉的，不会affect sound，最多是缺那个包而已。如果有任何inteference不管是线还是发送或者接收端都会造成crc校验错误的，写这些文章的人可能计算机知识都没学好，crc校验可能是1bit，甚至是3bit的，校验准确率为 100%- （2^8^3...

错包好像是不会重新发的。
waveform distortion好像也不是错包，只是会影响clock recovery，那么理论上如果用的是asynchronous mode就不是个问题，别的模式下理论上就会有影响的。

hugoo · Oct 28th, 2012, 10:14

引用:

作者: lighting

这么说吧，大家的台式电脑，天天在用，有谁非常得纠结 DVI 线的价位，抗干扰性，粗细，里面的芯是铜的还是银的？

没有吧！为什么？因为图像很清楚啊，没有什么不好，没人要想到买100刀的DVI 线，以达到更清楚的效果，因为大家知道，就这样了，不可能更清楚了。

HDMI 线就是DVI 线里的一部分...

答案很简单，发烧的都leave nothing to chances，宁可错杀一千，不能漏掉一个，不发烧的正常人难以理解很正常啦

线对显示器的影响很容易实时比较，有区别否，区别大否一目了然，没人敢吹牛，音频的东西，做实时比较困难就大多了.

sgyyz · Oct 28th, 2012, 10:49

引用:

作者: hugoo

你diy的bottlehead咋样了?

只完成了wood frame。那层polymerized tung oil finished还是很好看的。Component还没时间动手。工作忙。都神经病的。已经年尾要过冬了，反而比平常更巨忙。这年尾人人有钱没地方花。几十万的capital都想尽快找洞丢。都丢都我这里来。好像我很清闲。

sgyyz · Oct 28th, 2012, 11:22

引用:

作者: hugoo

错包好像是不会重新发的。
waveform distortion好像也不是错包，只是会影响clock recovery，那么理论上如果用的是asynchronous mode就不是个问题，别的模式下理论上就会有影响的。

这asynchronous也好像为了传输不中断，有个buffer。但并不担保资料是100%全对。网络里有两种protocols，TCP and UDP。TCP 如果丢包了就要重新传送。UDP就不是。UDP几乎都用在media streaming（realtime video/audio）还有VOIP。UDP如果packet loss严重（通常都是latency／jitter over long distance），media streaming quality是可以区别的。

这个USB audio streaming类似UDP。但我们用的USB线也就一两米吧。Error rate是多少？如果你换了那根GT2很可能可以听出区别。我自己是听出来了。但往往到了最后都是A线A声，B线B声。就这样而已。谁知道哪根是100%对？这些都是玩的，我自己可没耐性刨根究底。发烧度不够。玩过就算了。Whatever floats your boat。

奇怪为什么Discovery Channel的Mythbuster不做个audiophile的玩意。。。

hugoo · Oct 28th, 2012, 11:38

引用:

作者: sgyyz

只完成了wood frame。那层polymerized tung oil finished还是很好看的。Component还没时间动手。工作忙。都神经病的。已经年尾要过冬了，反而比平常更巨忙。这年尾人人有钱没地方花。几十万的capital都想尽快找洞丢。都丢都我这里来。好像我很清闲。

都是这样的啦，年尾突击花钱，我也被搞过，今年还好，没中奖。
DIY就慢慢来，不急，享受过程跟结果一样重要。

Oct 27th, 2012, 12:32	只看该作者 #25
hugoo Senior Member 注册日期: Jan 2008 帖子: 1,974 积分:11 精华:4 声望: 1172365	网上看来的。。‘’USB线听感不同的可能的技术原因。 -1- Waveform distortion: due to its physical properties, the cable can possibly affect the square waves, in interaction with the source and receiver (from that point of view they form an analog system). This in turns affect the accuracy of the recovered system clock fed to the DAC chip. This in turns affects the accuracy of the digital to analog conversion. -2- Interaction in between power supply lines and data lines: it has been measured that 1Khz spikes coming from the data lines can couple into the power supply lines and that the longer the cable, the stronger the effect. Such spikes could maybe be directly heard as noise depending on the dac's pcb layout. Such spikes could also affect the accuracy of the ICs inside the dac, resulting either in increased jitter (for the clock or the receiver chip) or directly in higher distortion (for the dac chip and the opamps of the analog section). -3- Rfi shielding: the usb cables are quite susceptible to high frequency noise pick-up (a reason among others why long runs cannot be used). Noise making its way into data line can perturbate the receiver chip, causing early/late triggers, resulting once again in a poorer system clock. If the noise couples into the power supply lines, see -2-. -4- HF noise attenuation: the source computer signal's quality can vary widely. HF noise can find its way on the various USB lines. A cable attenuating this HF noise could thus have an impact. It could however interacts with -1-. All these are sound engineering reasons and have been measured or could be, given time and the proper (read expensive) equipment. The fact that USB cables affect the analog output of the DAC seems to have been proven by measurements by Paul Miller for the january issue of Hifi News (if anyone has the article, I'd love to read more than hearsay). HOWEVER, the existence of a technical difference in between cables does NOT prove the existence of anaudible difference. It is even more so as the differences outlined above are fairly small and that cables manufacturers don't seem to bother measuring the actual differences their cables make. And you have to keep in mind before any generalization that USB audio uses 3 different protocols with various levels of weakness to those problems, that the USB receiver chips are very different and that DACs are coming from a bazillion different manufacturers who pay more or less attention to their designs. Sent from my GT-I9100M using Tapatalk 2
	------------------------------- You Cannot Be Serious!

Oct 26th, 2012, 23:08	只看该作者 #22
dalplex Senior Member 注册日期: Jul 2004 帖子: 7,488 积分:39 精华:18 声望: 2255410	银彩那个HDMI的演示我是听过的。我完全听不出任何区别。最后实在没什么好吹的，解释成每根线都是手工焊的。