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发表于 2005-6-30 00:19:42
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挑选音源的试金石《MY DISC》(我的碟)
摘自《电子报》2003.9.28 作者：小反
有没有不借助仪器就能试出器材性能的CD碟呢?回答是肯定的。由喇叭花唱片推出的《My Disc》(我的碟)就是这样一张猛碟。它不仅用于挑选音源，还用于整个音响系统的甄别、摆位调校以及煲机、练耳，用本碟的第33段—第42段，会把音源的极限状态考出来。
第33-41段为相同的爵士乐片段，第33段为标准电平0dB，以后每段减弱lOdB直到-90dB，第42段为完全寂静，在第33-37段之间还容易听得清晰每个乐音，随着声音越来越小，你可以逐渐开完功放的音量，把耳朵贴在喇叭上……。
这时音源的噪音也开始显现出来，器材的解析水平也将水落石出，最后乐器声越来越难显现出来，许多乐音将在噪声之中挣扎直到最后完全淹没在噪声中。有许多器材在后几段中将出现声音发破，或者有汽船声、电流声，或者是光头读碟时伺服电路工作发出的怪声，不一而足。我曾听到过有每秒响一次规则的“嘟呼”声(结果是显示屏电路秒闪干扰)，越好的器材越能听到高的段位，并且噪音越低越好，许多号称用 PCMl704作DA转换的CD机都过不了这关。
……(据说世界上最猛的解码器应能完整解出第 41段，并且在第4l段和第42段之间还能听出本底噪音有一点差别，那对我们来说只能是一种可望不可及的神话了)……
第42段的用处是绝对寂静，它和机器暂停时不一样。大家知道许多CD机在暂停时都要发出静音指令以切断输出(静噪门打开)，所以听第42段和机器暂停时不一样，前者是反映机器通路畅通时电路的噪声水平，器材的设计功底一目了然。
——市面上的VCD机在第38段还可以过(有的连第38段都解析不出来)，但噪声已成汪洋，一片沙沙声，很难辨出乐音来。第39段已成大海捞针，曾经去掉
过一机的OK电路，也只能是减低部分噪声，没有根本的改变，可见是D／A转换器的精度太低，机内数字、模拟、视频电路互相干扰。
——近几年来国产DVD设计上有了长足的发展，写这篇文章时测过最新款的单芯片DVD(机型：奇声 DVD8831——本机主观听音高频较硬)，本底噪声较低，在第39段弱音开始发破，第40段乐音开始调制噪声而引起声音完全变形(这可能就是本机主观听音高音较硬、毛的原因)，第41段静噪门打开(静音)，第42段3秒时静噪门关闭，本底噪声低到令人满意。
兴致中我还连续对比了几款奇声DVD，基本上第 39段和第40段都有类似的调制情况，在第41段和第 42段会出现静噪门打开的情况(静音)。当然，拿CD机的要求来强求价值几百元的DVD机可能勉为其难口巴。
——入门名机马兰士63SE(音色温暖)，这款机型听第38段的弱音有断音，第39段声音时断时续、打嗝(但不乱)，估计设计时对弱音打开静噪门(静音)，整机噪声较低，第41段和第42段静噪门打开(静音)，宁可让其无，不可让其乱，这也是它音色温暖的原因，即虽性能不是很高却深受乐迷喜爱的原因。
——在听过的器材中解析最好的要数奥斯1900解码器(声音中性自然灵动)，第40段较完整，极弱音已不能出来，第在41段乐音的强音能冒出几颗，但是没有乱的感觉，弱音已不在。印象极深的是这台机器本底噪声非常致密平和，这是印象中听过最利害的机器(按：此机设计者为原杭州中裕公司总工贺建华，现在美国加州硅谷的电脑公司工作)。
——在写这篇文章时还测过家里的SONY X333ES(音色厚暖)，采用磁悬浮线性伺服机心，模拟和数字电路独立供电设计，噪声水平极低，几近奥斯 1900的水平，但第40段中声音就开始断弱音(但没有乱的感觉)。本机播李娜《苏武牧羊》缺少奔放张狂之气，让笔者一直引以为憾，感觉李娜唱得平和，没有了野性，可是每次换上奥斯1900或DAC-I总能让人感动于这张碟的大气和奔放，场景历历在目，里面的人和物都又活过来一回，又重演一幕历史的千古绝唱……
——曾听过一款用双片PCMl704作DAC的CD机(声音动态凌盛威猛)，用本碟测试，在第39段声音已发毛混有许多高频噪声，第40段完全无法听清乐音，噪音和乐音交织在一起，机内虽采用双变压器数模独立供电，但设计排版布线有很大问题，此机售价虽高，但用本碟立现原形。
经过以上实测可以得出如下结论，乐迷选音源应选能完整听完第39段，有可能的话最好能完整听完第40段的机型(但银子已直线上升)，噪声可接受并和乐音不互相交调即为电路设计不错。最后要提醒大家，在用本碟测试时一定要注意音量的掌握，特别是在听第38-42段之前要先全面听一下这几段和第43段，并注意掌握好时间，以免听过了段位而损坏设备和耳朵。
CD: The Sheffield-A2TB Test Disc: "My Disc" - The Sheffield-A2TB Test Disc: "My Disc"
Sheffield Lab 10508-2-T
01. The Power of Seven - Up Front / Stranger In My Bed [0:03:51.07]
02. Thelma Houston - I've Got The Music In Me / Dish Rag [0:03:36.31]
03. Prokofiev's - Romeo & Juliet / Dance of the Knights [0:02:11.09]
04. Adam Makowicz with Phil Woods - The Name is Makowicz / Dirty Blue [0:03:43.17]
05. Michael Ruff - Speaking In Melodies / Wishing Well [0:05:37.16]
06. Lincoln Mayorga & Distinguished Colleagues - Vol. III / Dock of the Bay [0:02:50.72]
07. 1 KHz sinewave at -20 dBFS [0:01:05.38]
08. 1 KHz sinewave at 0 dBFS [0:01:05.02]
09. 20 Hz one octive warble [0:00:06.24]
10. 62 Hz one octive warble [0:00:06.01]
11. 125 Hz one octive warble [0:00:06.02]
12. 250 Hz one octive warble [0:00:06.02]
13. 500 Hz one octive warble [0:00:06.00]
14. 2.5 KHz one octive warble [0:00:06.01]
15. 5 KHz one octive warble [0:00:06.04]
16. 10 KHz one octive warble [0:00:06.00]
17. 15 KHz one octive warble [0:00:06.01]
18. 19 KHz one octive warble [0:00:08.57]
19. Person Counting from 1 to 25 [0:00:45.41]
20. Right Channel Identification [0:00:07.12]
21. Left Channel Identification [0:00:08.27]
22. Relative polarity between left & right channels [0:00:15.11]
23. Polarity pulses [0:01:00.51]
24. 1 KHz sinewave with bottom half clipped [0:01:05.12]
25. 3 people describing position on sound stage in stereo [0:00:34.46]
26. Same as track 25 except talking simultaneously [0:00:16.12]
27. Music for evaluating accuracy and focus of sound stage in stereo [0:00:13.12]
28. Same as track 27 except in mono (L + R) [0:00:12.56]
29. Same as track 28 except sent to left channel only [0:00:11.69]
30. Same as track 28 [0:00:12.11]
31. Same as track 28 except sent to right channel only [0:00:11.40]
32. Same as track 27 [0:00:19.01]
33. Music recorded with normal transfer level of 0 dB [0:00:47.24]
34. Music recorded withl transfer level of -10 dB [0:00:47.29]
35. Music recorded withl transfer level of -20 dB [0:00:47.26]
36. Music recorded withl transfer level of -30 dB [0:00:47.22]
37. Music recorded withl transfer level of -40 dB [0:00:47.27]
38. Music recorded withl transfer level of -50 dB [0:00:47.23]
39. Music recorded withl transfer level of -60 dB [0:00:47.27]
40. Music recorded withl transfer level of -70 dB [0:00:44.39]
41. Recording of Digital Black or 0 bits [0:01:02.34]
42. High Frequency low level alternating between 0000 & FFFF [0:00:37.14]
43. Correlated pink noise 20 Hz to 20 KHz [0:01:05.71]
44. Uncorrelated pink noise 20 Hz to 20 KHz [0:02:03.52]
45. Pink Noise raised in 1 dB steps every 3 seconds [0:00:25.02]
46. Pink Noise raised in 3 dB steps 4 times [0:00:17.11]
47. 1/3 octive Pink Noise at 25 - 31.5 - 40 Hz [0:00:33.64]
48. 1/3 octive Pink Noise at 50 - 63 - 80 Hz [0:00:30.74]
49. 1/3 octive Pink Noise at 100 - 125 - 160 Hz [0:00:31.57]
50. 1/3 octive Pink Noise at 200 - 250 - 315 Hz [0:00:32.31]
51. 1/3 octive Pink Noise at 400 - 500 - 630 Hz [0:00:31.46]
52. 1/3 octive Pink Noise at 800 Hz - 1 - 1.2 KHz [0:00:32.42]
53. 1/3 octive Pink Noise at 1.6 - 2 - 2.5 KHz [0:00:31.49]
54. 1/3 octive Pink Noise at 3.15 - 4 - 5 KHz [0:00:32.26]
55. 1/3 octive Pink Noise at 6.3 - 8 - 10 KHz [0:00:31.14]
56. 1/3 octive Pink Noise at 12.5 - 16 - 20 KHz [0:00:33.74]
57. 20 Hz to 20 KHz continuous warble [0:00:39.04]
58. 100 Hz to 20 Hz warble for subwoofer evaluation [0:00:42.65]
59. Individual frequencies from 10 Hz to 99 Hz [0:07:35.63]
60. Flat low distortion sweep from 20 - 200 Hz [0:00:26.37]
61. Flat low distortion sweep from 200 Hz - 2 KHz [0:00:18.64]
62. Flat low distortion sweep from 2 - 20 KHz [0:00:21.49]
63. Contains the musical note A (440 Hz) [0:00:35.39]
64. 100 Hz tone burst with duty cycle of 25% [0:01:06.61]
65. Same as track 64 except at 1 KHz [0:01:06.27]
66. Same as track 64 except at 10 KHz [0:01:06.42]
67. 100 Hz square wave [0:00:35.11]
68. Same as track 67 except at 1 KHz [0:00:35.14]
69. Full dynamics of the original recording [0:01:05.56]
70. Compressed version of track 69 with same peak level [0:01:05.72]
71. Tone with 0.03% distortion [0:00:15.01]
72. Same as track 71, except with 0.1% distortion [0:00:15.05]
73. Same as track 71, except with 0.3% distortion [0:00:15.03]
74. Same as track 71, except with 1% distortion [0:00:15.02]
75. Same as track 71, except with 3% distortion [0:00:15.04]
76. Same as track 71, except with 10% distortion [0:00:15.14]
77. Music with distortion of about 0.03% [0:00:35.02]
78. Same as track 77, except with 0.1% distortion [0:00:35.01]
79. Same as track 77, except with 0.3% distortion [0:00:35.01]
80. Same as track 77, except with 1% distortion [0:00:35.04]
81. Same as track 77, except with 3% distortion [0:00:35.02]
82. Same as track 77, except with 10% distortion [0:00:34.74]
83. Musical selection with no added delay [0:01:46.57]
84. Same as track 83 with 7 mS of group delay below 100 Hz [0:01:46.41]
85. Standing between Penske's pits and main straightaway [0:00:40.52]
86. Short walk down pit row of race car track [0:02:31.49]
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