45 degree LP stereo recording-A

 

Myav討論串有說：

quote:

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原發表者是 hckao2


何大英明, 是 LATERAL = L+R, VERTICAL = L-R
所以低頻, 人聲... 中央聲道者之震幅於 lateral 方向均倍增之(L+R).
反之於 vertical 方向均相抵之(L-R).

以下恕刪


.

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Stein 質疑說：

那麼以下這位日本Yosh桑說的要如何解釋？：
Specific to stereophonic groove of 45degree modulations, the amount of lateral displacement is always same as that of vertical displacement irrespective of amplitude and frequency differences between channels.

http://www7a.biglobe.ne.jp/~yosh/recspecs.htm

Sample of stereophonic groove: please note that top width of stereophonic groove is changing momentarily and that the minimum top width is depending on the displacement (amplitude) and the nominal top width of plain groove. Specific to stereophonic groove of 45degree modulations, the amount of lateral displacement is always same as that of vertical displacement irrespective of amplitude and frequency differences between channels. Hence cartridge to trace such groove should have same compliance laterally as well as vertically - though lateral compliance is usually higher than vertical compliance in most stereophonic cartridges.

這下不小心踩到hckao2的痛腳，換來回應說：

stein 兄,

報歉, 我雖然很想回答這個問題.
不過也不希望論壇倫為吵架場所.
所以要問問題請注意態度.
我沒義務回答不禮貌者的問題.
不是第一次態度不有友善者.... 道不同.

 

接著hckao2又說：

Very easy,
Yosh san made a "mistake".

lateral = L+R, vertical = L-R 當然不同.

if L+R = L-R,
then R = 0.
>>> not a stereo modulation

 

我也頂回去了：

我就直接、友善的說：
too easy to make a mistake for hckao2!
Yosh san did not make a "mistake".
L, V是波動變化的，像是交流電一樣，不能簡化成直流電一樣，直接相加、相減。


請再仔細看一下原圖裡

黃lateral displacement
藍vertical displacement
棕right wall 45 degrees
綠left wall 45 degrees

棕、綠，相加 得黃
綠、棕，相減 得藍
雖然畫得不很精確，但很清楚，用意到了。

就是 lateral 跟vertical displacement 變化雖然不同步，但幅度一樣。

 

何大也質疑說：

quote:

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原發表者是 hojuiyang111


the amount of lateral displacement is always same as that of vertical displacement irrespective of amplitude and frequency differences between channels

這句話對嗎?

如果 lateral = L+R, vertical = L-R .

如高兄所推演, L+R = L-R, then R = 0.

還是我們有何誤解嗎?

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hckao回答：

這個日本san說 :
"管它的啥頻率, 振幅! 水平與垂直的移動量都要相同"
他如果沒錯, 那要表達什麼呢?
當然是"錯"的!!

不過他要說些什麼不重要.
lateral = L+R, vertical = L-R 是定義沒啥好辨的.
如果這個都不知道, 不用功察資料.
那雞同鴨講就不必再深入了!!
您說是嗎?

Stein只好查資料了。

http://www.sickoftalk.com/whyvinyl_two.html

 

Recording Discs
(continued from page one)
Stereo Cutting Head

   
    The stereo cutting head consists of a stylus mechanically connected to two drive coils and two feedback coils, which are mounted in a permanent magnetic field, and stylus heating coil wrapped around the tip of the stylus (Fig. 12-10). When the signal is applied to the drive coils, the alternating current flowing through them creates a changing magnetic field, which alternately attracts and repels the permanent magnet.

Since the position of the permanent magnet is fixed, the coil moves in proportion to the strength of the field created and the attached stylus moves with it. The drive coils are so wound and mounted so that energizing either one alone causes the stylus to move in a plane 45 degrees to the left or right of vertical, depending on which coil is energized. Feeding both coils an in-phase signal causes the stylus to move in the lateral plane, while feeding the coils out-of-phase signals causes stylus motion in the vertical plane.
    The feedback coils are attached to the shank of the stylus and are, therefore, moved whenever the stylus moves. The motion of these coils in the permanent magnetic field creates a current flow in them, which is an accurate representation of the stylus motion. By mixing the outputs of these coils out of phase with the input signal in a technique called 「negative feedback」, several advantages are achieved.