Monday, February 26, 2018

AnalogMagik's VTA/SRA Tuning Function Really Works!

Hats off to Richard H. Mak for implementing this VTA/SRA tuning tool using the IMD-measurement approach! 

In theory this is easy but very hard to get right in practice. Before this tool shows up, many times I have tried to do various IMD measurements but could not get meaningful correlations between the SRA and the data collected, due to noisy data, etc. He managed to build a team to implement the right algorithm and filtering to get clean, usable numbers. So far I have confirmed that as I adjusted the arm height to change the SRA, I can actually get a knee point in the IMD curve and then binary search for the best possible setting. Also, the solution it gave is only slightly different from the original setting I got using a microscope, but the sound has greatly improved. Great job!

這個微調 VTA/SRA 的工具真的可用!太強了! 而且真的找到比用顯微鏡得到的設定還要更好聲音的點。我之前想要測量 IMD, 都得不到乾淨可用的數據,Richard 居然辦到了。目前的版本還有些缺點,但能到此地步,已經非常不容易。

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Using Acoustical System's head shell with adjustable VTA/SRA, I've again confirmed the VTA-tuning function of the AnalogMagik tool. When the SRA is about 5-degree off, the IMD numbers jump to almost 20%! Adjusting to reach optimal numbers, I measured the SRA at about 92.2 degrees. Note that the contact line/cantilever angle has previously been measured at 110 degrees with a microscope. The sound is now highly detailed while very relaxing.

用 Acoustical Systems 可調 VTA/SRA 的唱頭蓋,確認了 AnalogMagik 的調整 VTA功能,的確很厲害。當SRA偏離5度時,IMD 會到 20%!調整到 IMD 數值在5以內然後取得最佳值,這時得到SRA約92.2度,如圖3(線/桿夾角已經測出為110度)。此時,聲音的細膩度極佳。

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Monday, February 19, 2018

DS Audio Master 1 唱放,3組輸出的頻響測量

DS Audio Master 1光電唱頭的放大器,有3組輸出,提供不同的低頻衰減程度。我用 Adjust+的頻響測試得到的結果,整體趨勢與 HiFi News 在 2017 年12月的評論裡的數據類似,但高頻不像他們的那麼突起,比較平順一些。

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Setting SRA the Safer and Easier Way

I've been using the "direct SRA observation" approach for some time but found another method applicable to cartridges NOT YET installed on a tonearm: 1) use a microscope to first measure the angle between the cantilever and the line of contact on the stylus tip, say 110 degrees, 2) install the cartridge and apply normal tracking force, then place the stylus on the record surface, 3) use a smart phone or camera to take a close-up picture and measure the angle between the cantilever and the record surface, say 22 degrees, 4) using simple math, one can derive 180 - (110 - 22) = 92 degrees of SRA.

Overall, observing the cartridge's stylus before installation, then taking a picture of the cantilever on the record surface and measuring the angle between the two is relatively safe and easy, compared to observing the SRA directly.

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Friday, February 9, 2018

DS Audio 的 DS Master 1 光電唱頭抗滑設定

感謝 Maggie Chen 與 Jerry Hu 慷慨出借 DS Master 1 光電唱頭及唱放供測試評論,在來美前幾天抵達台北家中。

依慣例,在上主唱盤TechDas AF3之前,先上 Technics SL-1200G 做基本驗證評估。與先前短暫相處的 DS 002 一樣,對抗滑設定非常敏感。如果照該唱盤上,唱臂的刻度調到針壓1.7的位置,用示波器看,HiFi News 測試片的 TEST#7(B面最後一軌)右聲道還是有明顯失真,如圖。要再加到1.9左右,兩聲道才都會有圓滑的正弦波。


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