我现在知道了，玩黑胶一定要有把好规尺，否则90%的机率听不到好... [复制链接]

原帖由 hpstudio 于 2012-9-27 18:50:00 发表 也许10寸是个折衷的尺寸，Graham和Triplana都是10寸，FR64S好像也是。

这是综合各方面要素中，比较理想的长度。

超距和角度误差导致的失真是有实际测量的，看国外这篇文章的数据。




Alignment Errors
Although this issue is often conveniently ignored, accurate cartridge alignment is very difficult to achieve, not least because the overhang and offset have to be set within extremely tight tolerances if anything like the distortion behavior shown in the red trace of fig.3 is to be realized in practice.
Let's demonstrate this by assuming that we can achieve accuracies of ±0.5mm in overhang and ±0.5° in offset—tolerances that are extremely difficult to achieve in practice, particularly the latter. Fig.5 illustrates the variability in distortion vs groove radius behavior encompassed by this error range by plotting the results for the four combinations of maximum error: +0.5mm/+0.5°, –0.5mm/–0.5°, +0.5mm/–0.5°, and –0.5mm/+0.5°.

As the plots show, you can strike lucky. If both errors are in the same direction (+0.5mm/+0.5° or –0.5mm/–0.5°, red and blue traces, respectively), then their effects are almost complementary and the result is acceptably close to the optimum. But if the errors are in opposite directions (+0.5mm/–0.5° or –0.5mm/+0.5°, orange and green traces, respectively), then the results are very much worse. The point, of course, is that you don't get to choose: If your tolerances are ?0.5mm and ?0.5°, you are as likely to suffer a bad result as a good one.
The message to take away from this is a stark one: accurate arm/cartridge alignment is a high-precision process. Achieving distortion behavior close to optimal in practice is no trivial task.

这个图说明了超据和补偿角非同小可呀.


老外研究的真是到位,用数据说话.嘴上讨论听感永远是各说各话,以讹传讹的.

我们再来看看12寸臂与9寸臂失真曲线的差别。失真率12寸臂比9寸臂最大有27.5%优化！！这已经蛮大了。

Arm Length
Because increasing the effective length of the pickup arm reduces the curvature of the arc through which the stylus traverses the record, an optimally aligned 12" arm generates less LTE distortion than an optimally aligned 9" alternative. This is why 12" arms were traditionally favored for professional disc-transcription purposes.
But because the optimum overhang and offset are both smaller for a 12" arm, a given misalignment will have a larger effect. So let's repeat the exercise above and see what transpires with alignment tolerances of ?0.5mm and ?0.5° in the case of a longer arm. For an arm of 305mm effective length, the optimum alignment requires an overhang of 12.19mm and an offset of 17.15° (compared to 16.43mm and 23.02° for a 230mm arm), and gives the distortion plot shown in red in fig.6, with the equivalent for a 230mm arm (ie, the red trace from fig.3) shown in light blue for comparison. The additional 75mm of effective length has cut the peak second-harmonic distortion (at 10cm/s RMS recorded velocity) from 1.07% to 0.78%, a reduction of 27.5%. So far, so good.

Fig.7 shows the effect on the 305mm arm's distortion plot of misalignments of +0.5mm/–0.5° and –0.5mm/+0.5° (red and blue traces, respectively), again with the 230mm equivalents in the background for comparison (footnote 16). If we take the maximum distortion in each case, the results are as in Table 1. From these we can see that, in the +0.5mm/–0.5° case, the 305mm arm's improvement in peak distortion decreases to 13%, and in the –0.5mm/+0.5° case to 15%. If we increase the alignment tolerance to ?1.0mm and ?1.0°, then the 305mm arm's advantage is reversed in the +1.0mm/–1.0° case, and cut to 9% in the –1.0mm/+1.0° case—so honors are now about even with a 230mm arm on the basis of maximum distortion.

Table 1

Misalignment	Maximum Distortion (%)
	230mm arm	305mm arm
+0.5mm/–0.5°	2.36	2.06
–0.5mm/+0.5°	1.82	1.55
+1.0mm/–1.0°	3.07	3.35
–1.0mm/+1.0°	2.65	2.41

Whether a 12" arm's improvement in LTED is worth its higher effective mass, and reduced bending and torsional stiffness, has always been a judgment call. What these figures show is that unless a 12" arm is very carefully aligned, even that advantage can easily be squandered

天藏兄这个科学的文章引用,太有价值了,谢谢!

Because increasing the effective length of the pickup arm reduces the curvature of the arc through which the stylus traverses the record, an optimally aligned 12" arm generates less LTE distortion than an optimally aligned 9" alternative. This is why 12" arms were traditionally favored for professional disc-transcription purposes.


专业器材,以真实还原声音为目标,更多的依据数据.

民用器材,以好听为目标,更多的是主观听感.

二者目的不同,还原出来的结果就不同.有人就喜欢经过整容的美女,失真的声音,这也是人各有志.开心就好呀.

原帖由 jacky70 于 2012-9-27 18:42:00 发表 玩黑胶,一定要动手尝试和比较,不能仅仅停留在想象中和理论分析的,否则那是会误入歧途的.我敢说有人12寸都没有把玩过,都可以照样在论坛上高谈阔论的发表见解,这会误人子弟的.所以,还是自己尝试下,比较来的准确. ......

确实有感于此。
比对器材必须要在同一系统的前提下，特别是黑胶系统上的东西，不在同一系统下的比对几乎没有任何意义。
9寸臂短而感觉灵活，12寸臂长而感觉稳重，这是视觉上的感知，唱臂运动上的感知，并非听觉上的感知。完全出于同一设计唱臂，声音表现上12寸确实是占有绝对优势的，并没有任何木讷的感觉，并且由于循迹误差小反而会挖掘出更多的信息量来，因而空气感与鲜活度也会略优于9寸臂，而至于中低频，12寸臂则占有了绝对优势！  但12寸循迹上确实不及9寸臂灵活，适配性更远远不及9寸臂，因而我前期开发转轴式唱臂的最重要的工作就是让9寸臂尽量的去靠拢12寸臂的声音表现。即便推荐我也往往推荐9寸臂，因为9寸臂易玩易用！但如果深究起来，特别是在搭配大部分MC唱头的情况下，9寸臂在声音上基本占不到任何优势！

Jacky讲得对，像我同你虽然都是玩黑胶、都是喜欢跨洋过海从国外搬运洋垃圾回来，但出发点却是南辕北撤，我是唱片的奴隶、你是器材的仆人，广州话说的：大揽都扯唔埋，当然只能是各自精彩了。

应验了那句话:实践出真知,见多识广.


在实际玩黑胶系统过程中,绝对实践大于理论.原因很简单,也许我们的理论水平还是太初级了.既然不能从理论上,象天藏兄引用的那个老外那么专业和准确数据,就只好回到听感上了.

听感又是个各说各话的范畴,所以,网络上更是可以信口开河.

蒋鹏兄你试试在一个高分析力的系统上，用同牌子同系列的9寸、12寸臂，装同一个也是高分析力的唱头来播一段马勒试试看。

原帖由 我爱LP 于 2012-9-27 19:49:00 发表 Jacky讲得对，像我同你虽然都是玩黑胶、都是喜欢跨洋过海从国外搬运洋垃圾回来，但出发点却是南辕北撤，我是唱片的奴隶、你是器材的仆人，广州话说的：大揽都扯唔埋，当然只能是各自精彩了。

赞同我爱LP兄,都是奴隶和仆人,哎呀,都是黑胶惹的祸.