Dan Lavry本人对DA10用户常见问题的解答，可能与大家平时的认识有冲突！

stephen0831

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首先告诉大家一个不好的消息，最近发现LAVRY官网上DA10涨价了，从原来的975美元涨到了1148美元。这很不厚道，DA10性价比降低了。
不知道什么原因，也许DA10的定价打击了DA11，想推动DA11销量？DA11价格到没变。
还好我提前以975美元的价格买进DA10。

Dan Lavry本人在其官网论坛上对DA10用户常见问题进行了解答，很多观点可能与大家平时的认识有冲突！

以下是引用LAVRY的解答（本人英文水平有限，只翻个大概，有的部分就不翻了，有错误还请指出，谢谢），不代表本人观点。

[ 本帖最后由 stephen0831 于 2009-6-6 15:16 编辑 ]

stephen0831

数字输出，AES、光纤、还是RCA
I always prefer the XLR's with an AES signal. "Mechanicaly speaking" the connectors robust and "latched", so you can not accidently pull the cable... Electricaly speaking, the voltage levels are high enough to enable use of longer cables. Also, the XLR (AES) is balanced and uses transformer coupling, which as a rule is a good practice for isolating a unit from ground loops.
I tend to be very carfull when using RCA connectors. I use short cables, because the signal level is very low, and the SPDIF is unbalanced. But when using good and relativly short cable, it works fine.
Optical seems a bit more robust then RCA. The early Optical use to be poor from jitter standpoint, but it has improved a lot in recent years. Optical is a very good choice from isolation stand point. In fact, it provides a better way to isolate then a transformer coupled system. For computer interface, where isolation may play a role, optical is a very good choice, when the optical cable length is not too long.
Very often, one has no choice between sources. Some CD player may have an optical only, another device may have an only an RCA...
For long distances I would prefer XLR with AES signal, then the optical link second, and the RCA last.
For short distance and best isolation I would use Optical first, then XLR and RCA last.

Regards
Dan Lavry
大概意思：长距离：AES>光纤>RCA
                  短距离：光纤> AES> RCA
                  我更愿意选择AES接口，电学上讲，电压足够高，适合长距离传输.....
                  RCA要小心，要用短线，因为电平低，且是非平衡的。当然用质量较好的短线，问题也不大。

[ 本帖最后由 stephen0831 于 2009-6-6 15:17 编辑 ]

stephen0831

为何DA10只采用开关电源，采用环形变压器是否会增强音质？
I thought I am an audiophile. Does it mean that I must conform to what the majority of audiophiles think? Are there different kind of audiophiles? My "kind" are into good music and good sound  
I am well aware of the possible "marketing benefits" of doing things by the "generic audiophile rules". When I started with audio, I was quickly made aware of the rather long list of do and don't. The "funny" thing for me was how often I heard the phrase "it is so but I do not know why". "This sounds better but I do not know why". "That sounds better but I can not explain it". Of course the word "better" could be exchanged for image, depth, warmth and so on.
As an engineer, I just could not accept such reasoning. If you take that "audiophile list" to an extreme, then you must deny what you learned and experienced, you must avoid the urge to do a better job, because you agreed to follow a set of step by step rules like a robot. Your design will be made of certain preferred vacuum tubes or discrete circuits (no opamps), with least amount of negative feedback (that’s is nuts), powered by a toridal linear (and nothing else), the electrolytic are to be a certain preferred brand, the resistors have to be preferred brands, it has to run hot, glow in the dark and have at least one big Frankenstein knob...
Needless to say that many real serious advances in technology do not ever "make it" to the old "audiophile list".
You used the word "magic". In all fairness, why should I accept such magic, a dogma of "do and don't" coupled with "we do not know why"?
In an more ideal world, the users of the gear would prefer that I do what I do because I am a professional engineer and I "do know why".
In this case (the power supply), I do know why I chose to use a switcher. There are many "overwhelming considerations" why I used the switcher. I would not use it if a linear would be a better choice.
And BTW, if anyone thinks that a linear is costlier, they are wrong. As a rule, a switcher is costlier then linear.
I really do not have a big issue with any types of audiophiles. I prefer my type - do whatever it takes for great music and sound. But if the larger segment of audiophiles wants a big knob, that is fine with me. I see no crime committed. My personal preference is to go for best sound using whatever I can as a designer, and that always means one thing - I have to know why. There is no magic in engineering. It is not always all black or white, intuition driven by experience does play a role, and this statement true even for math. But following blindly is out.
I guess I did not answer your question in much detail. It would take a lot of time and space. Of course one can argue the advantages of a toroid (best containment of magnetic field), but then it has to be compared to the switcher which may have an advantage of a preferred frequency range (interfearance much above hearing), then there are heat issues (switcher is much cooler), and so on. At the end of the process, one has to compare the results in a well QUANTIFIED manner – HOW MUCH radiated noise and conducted noise is there, at what frequency (relative to the ear), what about the heat and its impact on the other circuits… And then one gets to look into adding solutions to the problems (such as additional filtering, supply location and orientation and much more)… There is just too much to be said that I can not put down in a post. It would take a whole book...
大概意思：我也是发烧友，但是否这意味着我一定要遵循大多数人信奉的所谓的“发烧思维定势”？我这类发烧友只关注好音乐和好音质。
我很清楚所谓的“发烧思维定势”会带来商业利益。我涉足音频领域不久后就发现发烧友的一系列“必须做”和“不能做”的有趣做法。我经常听到有人说“音质变好了，但我无法解释原因”。当然，所谓的“好”，也许是结像、深度、温暖等听感。
作为技术人员，我不接受这种思维，否则就意味着推翻自己的所学和经验。这种思维要求你像机器人一样，严格一步步按它的指示来做：你必须选用某型号的电子管或分立电路（不能有运放），必须要有负反馈（不可理解），只能用环状线性变压器，只能采用特定品牌的电解电容，电阻也是制定品牌，必须要预热，…
我想当今先进的科技可能也很难满足这种传统发烧要求。
……
你可以自己给DA10改装环状电源，但最好和开关电源比比，哪种得到的频响范围更大，还不用提开关电源发热量更小，环状电源噪音问题、对电路其他部分的影响，还需加入额外的滤波、电源位置、方位等等因素。
采用开关电源是有许多考虑因素的，如果环状线性变压器更好，我肯定会采用。不要以为开关电源就比环状线性变压器便宜。
我与任何一种发烧观都没有成见，但我坚持从技术人员角度出发，用能解释的知识来设计电路以获得更好的音质。当然，以经验的直觉来设计也没错，但盲从是不行的。

[ 本帖最后由 stephen0831 于 2009-6-6 15:10 编辑 ]

stephen0831

关于数字信号线材和RCA改BNC
Why do that?
Electrically speaking, the question is more about the type of cable then a connector. Both BNC or RCA can have good cable or a bad cable.
As a rule, the best cable is a short cable. A real poor 6 inch cable is better then 100 feet of the "best cable on earth". So the "golden rule" is to use short when possible.
At the frequencies and rise times of digital audio, there is no point in going beyond a certain bandwidth, which by the way has a LOT to do with cable length (especially with long cables). See "Skin Effect" under the tutorial section of this forum.
BNC is more robust mechanically, it is better for say a 1nsec rise time scope (that is 350MHz bandwidth)... but digital audio is slower then that.. the connector itself is not less then critical.

大概意思：干嘛这样做？电学上讲，与导线有关，与接口无关。最好的线是短线。6英寸的“鸡线”优于100英尺的“世界上最好的线”。所以“黄金原则”是用尽可能短的线。.....

[ 本帖最后由 stephen0831 于 2009-6-6 15:11 编辑 ]

stephen0831

同轴阻抗等问题
My advice: don't believe everything you read.
The statement: "75Ω is the perfect among three interfaces since its jitter is the smallest, BNC connector is better than RCA" is wrong.
The statement: "110Ω AES balanced plug is reliable but with limited bandwidth" is wrong.
The statement: "Those optical TA&T is an idealistic interface as its transmitter & receiver are the root cause of jitter (20 times of BNC)" can be highly misleading as well.
In short, ONE OF THE MANY mechanisms that may cause jitter has to do with the transmission of the digital audio. The mechanism is based on BOTH signal rise time and signal droop, which is in fact the upper frequency and the lower frequency of the transmission bandwidth.
The lower frequency is usually determined by the AC coupling characteristics such as AES transformer (mostly AES) or Capacitive coupling time constant (Mostly SPDIF).
In fact, very often, the high frequency capability of the link is higher then the signal rise time, making it a low frequency transmission capability (limitation) issue.
The transmission of signals requires understanding of electromagnetic fields, which takes some studying. Anyone with an appropriate exposure to the fundamentals of electronics (Maxwell’s equations and what they represent), understands the details of such transmission. It is unfortunate the people without a clue, feel free to “spit out garbage” straight out of thin air!
One of the common errors made by those that “spit out garbage”, is to view electronics as collection of parts, each part with “stand alone” characteristics. True, each part has it’s own characteristics, but it is the INTERACTION between parts that counts most.
It is possible that the “garbage maker” saw an application where say 75 Ohms had more bandwidth then 110Ohms, but making conclusions based on one case is ridicules! Everything needs to be put in context. You can find high speed internet cables such as Cat 5 cables with 100MHz bandwidth, CAT6 with 250MHz and the proposed CAT7 with 600MHz. They are all 110Ohm, twisted and unshielded. They are not 75Ohms.
A standard RG58 50 Ohm coax has more bandwidth then RG179 75 Ohm coax.
A standard RG59 75 Ohm coax has more bandwidth then RG178 50 Ohm coax.
The difference is dimensions, not impedance. The RG58 and RG59 are much thicker then RG178 and RG179, mostly skin effect issue. And there are times when it counts, especially for long cables. But it has nothing
to do with a connector, which comes into play at more then a few hundred MHz, when the signal rise time (bandwidth) gets into physical dimensions comparable to the connector dimensions (we are talking about around 150psec per inch, which is over 2GHz)... All of those connector considerations are way above digital audio!
The fact is: Take a typical AES or SPDIF signal, run it through say 100 feet of 110Ohms cable with an AES connector, or 100 foot 75Ohms cable, and in either case the bandwidth is more the 99.9% due to the cable, less then 0.01% due to the connector!
The connector alone has nothing to do with jitter. The cable alone has nothing to do with jitter. The issues making jitter are, as I mentioned already, the lower and upper cutoff of the transmission link, the termination tolerance, the cable impedance tolerance and more. The biggest potential issue is the skin effect (non issue at very short distances), which has to do with the dimensions of the cable, who much copper, how many wire strands and so on.
XLR, RCA and BNC are all circular connectors, all very simple structures. From signal transmission standpoint, one looks at it as a very short transmission path with a certain very small series resistance, small series inductance, and some small parallel capacitance. By adjusting the dimensions and the insulation material of a connector, one can get the desired impedance (somewhere between say above 30 Ohms, and if you separate the distance between conductors between here and the moon as high as 300Ohms).
For ideal cables: The impedance of a cable, or connector is the square root of the L divided by C where L is the inductance per unit length, and C is the capacitance per unit length… and so on.
Skin effect mucks things up at long cable length. I have a tutorial on this forum, under tutorial section…
I have some work to do, but will try and find time soon to post some material about signal transmission and cables. There is so much BS floating around, it begs for some reality.
Meanwhile, one is well advised to realize that BS is an international phenomenon.

尽信书（杂志）则不如无书。
“75欧时jitter最小，BNC 接口比RCA好”——错误。
“110欧 AES 平衡输入可靠，但带宽不够” ——错误。
“光纤 TA&T 接口过于理想化，因为它的传输器和接受器正是他产生JITTER的原因” ——误导。
无论是AES 还是 SPDIF，用过100英尺的导线，带宽99.9%受导线影响，0.01%受接头影响。
接头与jitter没关系。

[ 本帖最后由 stephen0831 于 2009-6-6 15:11 编辑 ]

stephen0831

以下是Dan Lavry助手Brad Johnson的解答

关于：XLR-to-RCA转接头
Simple XLR-to-RCA adapters are needed to connect the DA10 to RCA cables, We recommend the Neutrik adapters model NA2FPMF for this purpose. The DA11 is shipped with these adapters included
大概意思：推荐Neutrik NA2FPMF（网上搜了一下，7.52 美元一个）

关于：XLR直推耳机
What I have heard and seen was not so much that people were not happy with the headphone amp of the DA10, but that they felt they got beter results using the XLR ouputs operating in balanced mode to drive the HD650's.
I cannot say that I have had the chance to compare the two ways of driving the HD650's, but raising the output impedance (which is in effect what you are doing by using the XLR outputs) tends to introduce inaccuracies in the reproduction. It is entirely possible that someone might prefer the "sound" being less accurate, so even though it does not "make sense" from an engineer's perspective, it is possible that a less accurate system could yield a more pleasing result.
I have to say that in many years of dealing with high-end audio, I have found that more often than not, many people will choose a more distorted version as the "better" one. Ultimately, the important thing is that you enjoy listening. In the long run, having an accurate system is more likely to accomplish this goal; even if it did not sounds "as good" on first listen.
大概意思：XLR直推耳机将提升输出阻抗，导致声音重播的“不准确”，据我在high-end领域的经验，确有不少人更喜欢“扭曲”了的声音。当然，自己喜欢就行，但从长远看，准确的声音更有可能实现好听的声音，虽然初听上去没有扭曲的声音好听。

关于在XLR-to-RCA之间引入电阻器
We do not recommend using anything but a "hardwired" connection between the pins of the XLR connector and the RCA connector. It is very unusual for any resistors to be present in a simple adapter- is it possible that the CARDAS adapters are also attenuators?
We do not recommend using any form of attenuator or impedance "matching" of any kind in the adapters because they will raise the (effective) output impedance of the DA10, and this could result in interaction with cable (capacitance) that would lead to frequency response problems like high frequency roll-off.
大概意思：我们推荐固定链接的XLR-to-RCA，在之间引入电阻器不是常规做法。我们不推荐在XLR-to-RCA转换头中引入任何形式的衰减器或阻抗适配器，因为这样会增大DA10输出阻抗，并引起与导线电容的互动，造成频响问题，比如高频斜坡衰减。

[ 本帖最后由 stephen0831 于 2009-6-6 15:13 编辑 ]

stephen0831

原帖由 linuslv 于 2009-6-6 15:10 发表


那么Cardasna那么贵的那个有啥好呢？？

那得去问厂商，或者另一派“发烧友”了，反正LAVRY恐怕没法给你解答。
当然，换线、换接头带来的听感变化是客观存在的
注意，只是“变化”，但是否一定是更准确的声音，或者音质提高，就不知道了。

[ 本帖最后由 stephen0831 于 2009-6-6 15:23 编辑 ]

nadesicozhao

“专家”也有胡扯的时候

渔歌

至少开关电源这块绝对是DA10的软肋

小白

Lavry不用环牛确实应该不是为了省钱,而是有他自己的考虑.  开关电源有它自己的好处,比方DA10解码器有着极宽的适用电压,不论是中国,日本,美国,欧洲,到处插了就用,无须变压器,这就是一个优点. 另外开关电源有一些好处,比方发热小,Lavry也提到了.  

Lavry这个人很有个性,有个性的人,一些想法或许不能完全"理喻",就象他所说,要是换成环牛,声音会如何,有条件的不妨自己改制一下. 现在用开关电源的HI-FI制品不在少数,有些还是很高级,昂贵的制品,所以Lavry并不孤独.

渔歌

小白说的都是减低成本和取巧的做法

没看出哪里为音质考虑了

事实也证明了DA10的开关电源导致DA10的声音很不稳定，要动用电处才行

渔歌

高级的那些制品的开关电源难道和DA10用的是一样的么

这种说法偷换概念了

便宜的PC电源才100，好的要千多，都是开关电源，呵呵

打死不发烧

算了DA10既然胀了，放弃它吧。反正国内卖的也不便宜吧。
还是选择DAC1好了，毕竟DAC1在国内，商家的利润已做的很低了。

stephen0831

原帖由 小白 于 2009-6-6 16:31 发表
Lavry不用环牛确实应该不是为了省钱,而是有他自己的考虑.  开关电源有它自己的好处,比方DA10解码器有着极宽的适用电压,不论是中国,日本,美国,欧洲,到处插了就用,无须变压器,这就是一个优点. 另外开关电源有一些好处, ...

我也觉得他挺有个性的，且不论他的观点是否绝对正确，至少他不忽悠，走技术派路线。按理说少谈技术指标和原理，多谈听感，进行忽悠的话，他可以转更多的钱。
他也是最先指出CD格式存在JITTER问题的人之一，当时业界还在大肆宣传CD格式相比模拟多么优越。
不是每个烧友都是富翁，花钱理性些更好。

[ 本帖最后由 stephen0831 于 2009-6-6 16:58 编辑 ]