Thursday, May 17, 2018

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.


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Tuesday, May 1, 2018

"Powerful Bass" of Phono Stages?

When some people/reviewers commented certain phono stage has "powerful bass", it's better to take it with a grain of salt. Unlike pre-amps or power amps which do not have any EQ circuit in their signal paths, a phono stage has a reverse-RIAA EQ built in. And some designers will "cheat" a little by tweaking the EQ curve to achieve the desired "sound" for the device. So when we find a phono stage to have very impressive bass performance, it's likely not from the superior circuit design or strong power supply unit, just a trick of modifying the EQ. 

The three phono stages tested below are all priced at the ~8000 USD range. Using the same cartridge Lyra Kleos (without changing any parameters) to feed the test signal, I measured the high-frequency responses to be virtually identical. Whereas below 5kHz, the 2nd and 3rd devices obviously display higher output levels, ranging from a couple of dB to the extreme case of nearly 5 dB at the lowest end of the spectrum.

Incidentally, the first two are UK brands, and the 3rd one from the USA. In my experience, phono stages made by the US-based brands tend to have boosted bass responses similar to the 3rd device.

前後級擴大機沒有等化線路,而唱頭放大就必須有「反」RIAA等化。低頻很厲害的唱放,其實可能只是在等化曲線上做了些手腳,並非它的線路或電源部分有多特別。如下面3個圖的比較,用同一個唱頭不改變任何參數,得到的高頻響應幾乎完全相同。但 5kHz以下的,就開始出現明顯的差異。這3台的美金定價都在8000左右,前2台是英國牌子,第3台是美國的。