AC noise from elevator

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AC noise generated from the building's elevator moving, is quite visible from Chart#2 compared to the baseline Chart#1. The so called "EMI Meter" from Green Wave also reports up to 1000mV of noise compared to the baseline's 46mv. Unfortunately, no AC filter including the one from Green Wave, or even an ISO transformer can block such noise.

建物裡的電梯動作時產生的電源污染，可以從比較兩個附圖裡看出。那個號稱測EMI的錶，也顯示超過數百甚至上1000的數值，比平靜時46高出很多。而且所有的濾波裝置，甚至隔離變壓器，對這種頻段的雜訊似乎都沒什麼效果。

Tracking Ability of an Old Decca Cartridge

（中文在後）The Decca family of cartridges are often said to have poor tracking ability. In fact, with proper anti-skate force, at least in standard tests they track better than many MC cartridges. But when they mis-track, the distortions are more offensive to ears. Here in the first spectrum chart taken when running a typical tracking test, the old SC4E shows the typical Decca-family behavior of having higher 3rd harmonic distortion which is less pleasant than the 2nd. This is just the opposite of most other cartridges. In the second chart, the SC4E is put through the maximum signal strength of +18dB and it still manages to play through the whole track with manageable distortion levels, better than many MC cartridges.

許多人說 Decca系列唱頭循軌不好。其實如果抗滑設定對，至少在標準循軌測試，會比許多MC唱頭的循軌表現好。主要問題是，它們的三次諧波失真比二次高，這與大多數唱頭相反。耳朵會比較容易聽到奇次失真，所以容易察覺它微小的循軌問題。第1個頻譜圖是正常強度的測試，顯示這典型Decca唱頭的失真行為。第2個圖是用最強的+18dB訊號測試，顯示這個老唱頭還可以相當穩定的唱完，而且整體失真還不差，不像一些MC唱頭會出現很不堪的波型。

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".