The Perils of Using Tangential Arms -- Follow Up

（中文在後面）
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?

 （中文在後）

 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。

Steep Angle Needed for a vdH Black Beauty

This vdH Black Beauty needs plenty of tilting forward. With its top level, the IMD is unacceptably high at about 12%. Lowering the arm high makes it even worse. Raising the arm on the SL1200G to the limit and slight improvements start to show. Eventually need to shim 3 pieces of cards in its front to get the numbers into the 2 to 3% range.

這個 vdH Black Beauty，調整到上緣水平時，IMD竟然高達12以上！降低一些更差，到14。SL─1200G的唱臂調到最高，稍微好一些到11左右。最後竟然前緣要墊3張名片的厚度，才到不錯的數字範圍。

AnalogMagik's Tracking Force Function

（中文在後面）
After finished writing the Part-1 of AnalogMagik review, I started to test the remaining features I haven't spent much time on. The Tracking Force function are verified on two cartridges here, Lyra Kleos (recommended VTF=1.73 according to the user manual) and DS Audio DS 002 (recommended VTF=1.7). Figure 1 is the final VTF for the Kleos after optimizing for the lowest THD using AnalogMagik. Figure 2 is for the DS 002. For the Kleos which is my main reference cartridge for the past 2+ years, even though the change is only -0.04g from the original setting, the sound has become much more refined with high-frequency extension unheard before. Similar improvements are also heard on the DS 002, but somewhat less drastic even though the change in VTF is much greater.

第一部份的評論交稿之後，開始測試 AnalogMagik其它還沒仔細研究的功能。Lyra Kleos（廠方建議針壓 1.73）最佳化後的針壓如圖一，DS Audio DS 002 （廠方建議針壓 1.7）最佳化後的針壓如圖二。調整後，兩者高頻變得細膩很多，尤其是已經用了2年多的 Kleos比起之前，「高貴感」進步幅度相當明顯。

New cartridges should all come with photos like these

The two cartridges belong to my friends. In my inspection I believe the cantilevers were both overly steep, resulting in the SRAs in the +96-degree range when the top surfaces were level. After adjustments at the factory, they came back included photos showing much more reasonable angles. For the cartridge manufacturers, providing such photos should be fairly easy, and such material will greatly help the users in correctly setting up the devices. Additionally, this makes monitoring the health of the cartridge much easier over time.

Note the angle of the coil is now only slightly away from parallel to the pole pieces. Adding tracking force and drag should put it into near perfect angle.

這是兩個針桿太陡的唱頭，原廠調整後寄回來，他們所附的照片。強烈建議所有新唱頭都應該附上這樣的照片，對用家來說會少很多調整上的麻煩。日後也容易追蹤健康狀況的變化。

注意現在線圈的角度，只偏離磁鐵的平面一點，加上針壓等外力，就應該與前後的磁鐵平行了。