Saturday, November 10, 2018

London Reference Cartridge with Custom-Made Phono Stage

(中文在後)
After a long hiatus, the Decca-series's London Reference is now back in action, with a custom made Tom Evans MM phono stage (the only one in the world according to TE). This phono stage has an RIAA curve and load settings targeting the Decca cartridges. The frequency response measurements indeed indicate the effectiveness in smoothing the curve, especially the bass region. Figures 1 and 2 are in linear scale, showing the same cartridge pairing with the TE and iFi iPhono 2, respectively. Figures 3 and 4 are in log scale. Note the high frequency part may be further tweaked by the capacitance setting.

Decca 系列唱頭 London Reference 經過一段時間沒用,又再次回來,搭配特別訂製的 Tom Evans MM 唱放。這唱放有特別為 Decca 唱頭設定的 RIAA曲線及阻抗/容抗負載。頻響測量得到相當平直的正負2dB結果,線性X軸如圖一,圖二是用 iFi iPhono 2的對照。圖三圖四是對數X軸。高頻部分,應該可以用電容負載再微調。

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Friday, November 9, 2018

Two Cases of Skewed Zenith

(中文在後)
Is it always a good practice to align a cartridge with its cantilever parallel to the reference lines on the protractor? In the two cases shown here, probably not. In fact in both these cartrdiges, the builders seem to be aware of the skewed zenith angle and install the cantilever slightly at an angle to compensate for the skew.

用唱頭的針桿來對準尺規,而不用唱頭外殼為準,是許多「專家」會堅持的。但看這兩個相當高價的唱頭針尖,底部的zenith角有明顯偏差。如果用針桿來調整,顯然不會得到最佳設定。而在這兩個唱頭,製作者似乎知道有這個誤差的情況,而將針桿安裝偏一點角度來補償,而非平行於唱頭外殼。所以如果看到一個新唱頭的針桿不太正,或許是有其背後道理的。

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