음향 일반 - [ 펌 ] 마스터 클럭 이 필요 한가요 ? 음향 	 워크 샵 
 [ 펌 ] 마스터 클럭 이 필요 한가요 ? 
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 The diagram on the opposite page Short ‑ term timing variations between one clock period and the next can result in a distorted waveform . shows how short ‑ term timing variations between one clock period and the next can result in a distorted waveform . If the timing variations are random , the result is effectively added noise , whereas if the variations are periodic , additional atonal ( intermodulation ) artifacts can be added to the signal . These timing variations are referred to as ' jitter ', whereas a long ‑ term timing variation of the overall clock rate is called ' drift '. 
 The first unit I tested was the Behringer Ultracurve , and the resulting graph is shown on page 127 . The Behringer unit on test here worked less well when clocked to a high ‑ quality external master clock than on its own , inferior internal clock . The pink trace shows the performance of the unit running on its internal clock and with a 1 kHz tone input at about ‑ 4 dBFS . The spikes to the right of the 1 kHz tone indicate some harmonic distortion below about ‑ 106 dBFS , but the trace is relatively clean of other spurious unwanted signals , all of which lie below ‑ 130 dBFS . 
 This is not an unusual situation by any means , and the reduction in audio quality is not related to the supposed quality of the reference clock source either . The graph on page Like the Behringer device , the Focusrite ISA 428 performed better on its own internal clock than on either of the two master clocks ( Antelope and Drawmer ) it was sync ' ed to . compares the Focusrite ISA 428 running on its internal clock at 48 kHz ( dark ‑ blue trace ) , with external 48 kHz clocks from both the Antelope Trinity / 10 M clock combination ( green trace ) and the Drawmer MClock Lite ( yellow trace ) . These two master clocks represent the two cost extremes of all the master clocks available for this test , with a 12 : 1 price ratio between them ! 
 The obvious conclusion is that in simple digital audio setups a master clock is usually unnecessary , although it remains critical that multiple digital devices are clocked sensibly . In more elaborate digital audio systems , a master clock can make the task of slaving multiple units much easier and neater , and allow the system to operate more reliably . In systems where digital audio is being used in synchronism with video , an appropriate master clock is absolutely essential . But in any of these cases , the use of a master clock will not improve the audio quality achieved by the converters in any technical sense — and the most expensive clocks fare no better in this regard than the least expensive . The only relevant criteria for purchase is whether the clock provides the facilities , inputs and outputs required , and is designed sufficiently well to conform with AES 11 Grade 1 standard . . 
 Isochrone Trinity $ 3995 
 Isochrone 10 M $ 6495 
 Big Ben $ 1340 
 SynchroGenius HD Pro $ 3063 
 MClock Lite $ 1055 
 MClock Plus $ 1725 
 iClock $ 1475 
 Nanoclock $ 1300 
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