圖1底下的說明
Starting with RME ADI-2 Pro, we see the same problem with random low frequency noise around our main tone at 12 kHz, resulting in that "skirt" around it. RME has since upgraded the clock both the Pro and DAC version so that problem is no longer there. I confirmed that in the DAC review but not in the Pro as I don't have that version as you see in that review
很清楚表示作者測量的是ADI-2 Pro,不是fs,但確定fs已經修正了skirt的問題,如圖2
如果將圖2的黃線(ADI-2 DAC)與圖1的紅線(DAC3)相疊,可以發現兩者都沒有skirt,雖然DAC3有較低的noise floor,但由於有兩個非常明顯的sidebands,所以ADI-2 DAC的jitter test表現要好過DAC3
然而,zjzju仍然不死心,明明圖2在原文就在圖1正下方,不用,拿了圖3宣稱圖1的藍線是fs版本,企圖矇騙過關
至於真相呢?只要沒瞎的人都看得出圖1與圖3兩者X軸精度完全不同。
稍作計算即可得知,圖1一個像素表示22hz,圖3一個像素表示11hz,換言之,圖3的精確度是圖1的兩倍,用圖3的比例尺,DAC3一樣會產生明顯的skirt