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]

后来我自己从美国订了一把类似的规尺，同样好用！

这是我收集的国外规尺资料，供大家参考：

从资料看，这类规尺采用的几何原理基本相同。

特点如下：

1. 可以同时用于唱臂和唱头调整，特别是安装新唱臂，那更是必须的工具。
2. 调整唱头精确，使用方法简单，一部到位。比拿着手电筒左瞧右瞧简单多了。
3. 即使你不知道唱臂参数也能调整出失真最小的效果。

原帖由 hpstudio 于 2012-9-25 17:31:00 发表 好贴，必须要顶！ 天藏兄居然有奶酪臂，牛！

这不是我的臂，网上扒来的图。


看看下面的黑胶坑纹图，对玩黑胶来说，误差真的是很要命的东西。

我有一只SME3009 SII早期版唱臂，在网上查到的资料是：
  有效长度: 228.6mm
  超前距: 15.14mm
  轴间距: 213.46mm
  补偿角: 22o

按以上参数怎么调都不对，后来用Dr.Frickert Protractor规尺调出来的参数与现在蒋兄公布的参数基本一致！！

我买的这把规尺是依照dennessen几何设计的，在美国还有专利注册，一般规尺都是需要两个校正点，这个只有一个，不知道具体的几何原理是什么？
DENNESSEN Alignment tool: US Patent 4,295,277 (Year 1981). Trade name "GEOMETRIC SOUNDTRACKTOR"

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.

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