AC Noise from Home Lighting

（中文在後）Among various lighting options for the listening room, LED bulbs (right) are probably better than the compact fluorescent type (left). As shown in the first AC spectrum chart, the fluorescent bulb creates visible noise spikes in the near 50kHz region as well as higher order harmonics. The 2nd chart is the baseline with no light turned on, and there's no visible difference when the LED type is used.

如果聆聽室的照明燈光有選擇的話，LED燈泡（右）應該會比小型日光燈泡（左）好。頻譜圖1顯示日光燈泡會產生50kHz附近的雜訊，而且還有更高的諧波。圖2是未開燈的數據，與用LED燈泡時幾乎無差異。

One reason why Decca-family cartridges are difficult

（中文在後）One reason why the Decca-family cartridges are difficult to tune optimally is the sizable gap between the lateral and vertical compliance numbers (Fig. 1). With most tonearms, the lateral resonance tend to be lower than the 8--12Hz ideal range (Fig. 2) while the vertical too high (Fig. 3). Adding/subtracting mass will aggravate the situation in either of the directions.

Decca系列唱頭很難調整好的其中一個原因是橫向與縱向的順服度差異大，如圖1。在多數唱臂，會造成橫向的共振頻率低於8到12Hz的理想值，而縱向會太高。而加/減質量都會造成其中一個方向惡化。

Good example demonstrating relationship between cartridge's compliance and resonance frequency

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A good example demonstrating the relationship between the compliance of a cartridge and the resonance frequency of the arm/cartridge combo. Here the cartridge has a horizontal compliance at 15*10^-6 cm/dyne, and the measured lateral resonance is at 10Hz. Its vertical compliance is lower at 12*10^-6 cm/dyne, and the measured vertical resonance is at 12Hz. BTW, the arm is a uni-pivot design so the effective mass in each plane should be very similar.

唱頭的順服度與裝在唱臂上時的低頻共振頻率的關係，這是個好例子。它的水平向順服度是15*10^-6 cm/dyne，縱向是比較低的12*10^-6 cm/dyne。在單點軸承唱臂上，測得水平向10Hz，縱向12Hz。理論與實際數據算相當吻合。

Measurements at an Audio Showroom Lacking Low-Frequency Energy

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Figures 1 and 2 are for the Left channel, 3 and 4 the right channel, frequency response and bass decay data. The green line in each frequency response curve shows the phase response. 

The bass region below 60Hz is indeed down 10 to 15 dB, unexpected of such sizable speakers. The differences between channels are also quite significant, likely due to the asymmetric room shape. 

圖1，2是左聲道，3與4是右，頻響及低頻殘響數據。綠色線是相位響應。喇叭算很大，而60Hz以下的確是凹下，伴隨較高頻率的凸出，屬於典型的房間與喇叭交互作用。左右聲道的低頻明顯差異，應該來自不對稱的喇叭後方牆角。左後方的牆角相當近，應該是主要問題來源之一。

A tonearm that can do "Signals Reproduction 100%"?

This tonearm's flyer (from years ago) showed some interesting data and pretty tall claims, such as "Signals Reproduction 100%", "Dynamic Improvement 5dB" and "fluid damping...eliminates all vibrations including rumble during playing".

Another case of cartridge spec not agreeing with actual product

（中文在後）Another case where the spec does not agree with the actual product. When the top of the cartridge is near level, the cantilever is close to 30 degrees, quite far from 23. Though given the angle between the contact line and cantilever is close to 120 rather than the more common 110 degrees, the SRA still ends up just slightly higher than 90.

又一個規格與實際不符的情況。當唱頭上緣接近水平時，針桿角度約30度，遠高於23。但還好它的線／桿夾角在120度左右，所以此時SRA只比90度高一些。

Turning off sub-sonic filter when measuring cartridge-arm resonance

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Some USB sound boxes/cards, preamps, and phono stages have subsonic filters to suppress ultra low frequency noise from playing record warps, etc. When measuring the natural resonance of a cartridge-tonearm combo, be sure to turn the feature off, otherwise one may get incorrect readings. Figure 1 is with the filter turned ON in the ART USB Phono Plus while Figure 2 is OFF and shows better results.

有些USB音效盒，前級與唱放有超低頻衰減功能，播放不平的唱片時可保護喇叭或其它器材。但在測量低頻共振點時（Adjust+ 裡的 f res功能），要將這功能關閉，才不會影響結果。圖1是ART音效盒的濾波ON，圖2是OFF。後者明顯得到比較符合預期的結果。