What do the magnet and pole pieces in an MC cartridge look like?

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What do the magnet and pole pieces in an MC cartridge look like? Figure 1 and 2 show a typical example. The cylindrical part is the magnet, and the attached metal parts are the pole pieces. Figure 3 and 4 show the ultra compact version, where the middle dark-colored piece is the magnet and the shiny parts are pole pieces. After the pole pieces are attached to the magnet, they need to get magnetized using an electrical device, as in Figure 5, before the whole assembly can be used.

典型MC 唱頭的磁鐵與磁極，如圖1與2。圓柱狀的部分是磁鐵，其它前後金屬部分是磁極。圖3，4是特別縮小的設計，中間暗色部分是磁鐵，前後是磁極。在組裝成唱頭之前，磁極必須用工具經過灌磁的手續，如圖5。

 

Speed stability test results on Technics SL-1000R, Part#2

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Technics SL-1000R speed stability data reported by the PlatterSpeed apps on iPad. No doubt this turntable is for now the world champion in this category. As references, the 2nd chart is the measurement on my SL-1200G. For people who don't consider speed stability as an important attribute of a turntable, do find a chance to listen to the sound of a solo piano or violin playing through this turntable.

用 iPad 上的 PlatterSpeed 軟體測試 Technics SL-1000R 的轉速穩定度，果然真的是目前的世界冠軍。比 SL-1200G（圖2）又更準一些。認為轉速穩定度不重要的人士，建議找機會聽一下這台唱盤播放出來的獨奏鋼琴或小提琴聲。

Speed stability test results on Technics SL-1000R

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Speed stability test results on Technics SL-1000R using AnalogMagik. As I mentioned before, flutter == 0.05% is the lowest number I've seen using AM for measurements, similar to what I got on my SL-1200G. If the PlatterSpeed apps is used instead, most likely we will see 0.015%. BTW, this is the best stability of all turntables I've tested so far.

這是用 AnalogMagik測試 Technics SL-1000R的轉速顫抖率，得到 0.05%，與之前測試 SL─1200G的幾乎一樣。若是用 PlatterSpeed來測，應該會得到 0.015%。這是所有我經手過的唱盤裡最佳的數值。

僅作參考：一台很新的K牌金色重量級唱盤，測得數據是：

The Perils of Using Tangential Arms -- Follow Up

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The Perils of Using Tangential Arms -- Follow Up

The owner of the cartridge followed my advice and sent the cartridge to the manufacturer. It has just been returned and, upon inspection, I was shocked to realize how much of the original stylus shank had been worn out (Fig. 1) compared to the newly installed one (Fig. 2). For those "gurus" out there recommending air-bearing arm users tune the air pressure lower to get "fuller bodied" sound, please take a look at the two photos and reconsider your stance on the matter.

Here's the earlier post for reference:
http://bingrungtsai.blogspot.com/…/the-perils-of-using-tang…

唱頭的主人聽了我的建議，將它寄回原廠，現在已經回來了。我在顯微鏡下看了之後才驚嚇地發現，和新的針尖（圖2）對照比較，原先的針尖（圖1）磨損掉的部分，比想像中還大很多。雖然磨損這麼嚴重，當初測試聆聽時，在聽了一個多小時後，才開始察覺到弦樂高頻有些許沙啞感，而且這還是因為我累積了一些這方面的聽感經驗，才會開始懷疑。所以除非用顯微鏡定期檢查，多數人對所用的針尖已經磨損，都很少察覺。而建議將氣浮臂的氣壓調低來得到比較「厚聲」的「達人」們，在看了這兩張照片後，是否要重新考量一下？

先前的背景資料：
http://bingrungtsai.blogspot.com/…/the-perils-of-using-tang…

Instrument-Based Method to Troubleshoot Hum

For years I've been advocating using instruments to aide troubleshooting hum issues, especially in vinyl playback systems. Due the diversity of component designs/implementations, the hum may be from the most unexpected causes/sources, and very often the resolution can only be found by trial-and-errors and step-by-step reductions before reaching the best outcome. Here's another recent example in my system.

After replacing the stock PSU for iPhono2 with a beefed up Acopian unit, I am quite happy with the sonic improvement, but when standing close to the speakers I can hear some humming, more prominent than my other phono stages such as the Avid Pulsare II. Even though no one can hear it at the listening position, I know the issue has to be addressed to reach optimal sonic performance, because the hum is just an indicator of how easily all kinds of unwanted noise can get into the system.

This morning I hooked up the measurement setup, and after trying out various grounding connections, I finally found the solution. Again, the best configuration is quite unexpected, and may not work at all in another system.

Before:

After:

Turns out in the case, it's best NOT to ground the Acopian PSU and the iPhono2 chasis. Using the relative scale, one can easily see the reduction in each step.

Both grounded, the 60Hz component is set as 0dB: 

Disconnecting the ground wire on the Acopian PSU gets about -7dB:

Disconnecting the iPhono2 chassis ground gets roughly another -2dB:

The Perils of Using Tangential Arms?

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 Among all the cartridges (>100) I've inspected for friends in the past few years, only 4 showed obvious stylus wear.   Interestingly, 3 of them  were installed on air-bearing arms, the other on a tangential pivoted arm. The photos below are from the most recent case,  showing a chunk in the right-channel side of the stylus chipped away. According to the owner of the cartridge, he followed the advice from an "expert" and adjusted the air pressure to the arm  lower to get "fuller bodied"  sound. 

I believe there is nothing intrinsically wrong with those arm designs, though one should definitely pay more attention to the setup and maintenance aspects. Especially with the air-bearing type, any issue in the air transmission lines can put huge stress on the cartridge and its stylus. 

在幫朋友檢視過的這麼多唱頭之中，真的見到針尖磨損的情況，其實非常少，嚴格講起來算有4個。但無獨有偶，其中3個是裝在氣浮正切臂，而一個是裝在支點正切臂。3支氣浮臂是不同廠牌出品，所以並非哪一支臂的特有現象。附圖是最近觀察到的一個例子，可以看到，針尖右聲道那一側（圖1,2裡的左側），有明顯的缺角。根據主人的說法，他按照一位「達人」的建議，將氣浮臂的壓力調比較低。可能因為如此，在播放唱片唱臂向內移動時，外側（右聲道）一直承受比較大的壓力。

我在之前（音響論壇348期）也說過，直線正切臂（氣浮臂包含在內）的先天缺點之一，是所有的質量都在支點之前，因此有側向力時，唱頭針尖會受到很大的壓迫。而支點正切臂，這方面雖然比較不會造成問題，但因為機械構造複雜，可動部分受到灰塵或溫濕度影響，動作受到阻礙的機率會比傳統支點臂來得高很多。因此，使用這類唱臂的人士，應該要定期檢查保養，特別是氣浮臂，整個供氣的通路一定要確保清潔通暢，壓力要合乎原廠規格。而且在聽到有任何循軌異常時，立刻停止使用，做全面的檢測。

至於唱頭的健康狀態，我一直主張要每半年測量數據，持續追蹤變化。如果有明顯改變，就應該拆下來用顯微鏡仔細檢查有無異狀。這對正切臂的使用者來說，尤其重要。

Before-and-After Data of Cartridge Adjusted by Manufacturer

Before-and-after comparisons of a cartridge that, based on my assessments/recommendations, was sent back to the manufacturer for adjustments in its cantilever angle, etc. Looking at the differences in data below, most people will have a hard time believing they are measured on the same cartridge.

上次兩個被我判定針桿太陡的唱頭之一，原廠調整角度寄回之後，今天去測了新的數據並做了azimuth等參數的微調。看了前後數據的差異，很難相信是同一個唱頭。