![]() That's why it's best to run an A‑D from its internal crystal clock, rather than an external master clock, if possible, and why good D‑As go to so much trouble to isolate and remove interface jitter. In both of these situations, the signal is being converted between the analogue and digital domains, and precise, jitter‑free sample-clock timing is, therefore, absolutely essential. Where interface jitter becomes important is in the D‑A conversion stage, or when clocking an A‑D converter from an external master clock. Moreover, it doesn't actually matter in the case of transferring digital audio from one digital machine to another, anyway, provided all that is required is to identify each data‑bit value reliably. The diagram above, courtesy of Prism Sound, illustrates the effect.įortunately, interface jitter can be removed fairly easily using phase‑locked loops (PLLs) or other, often proprietary, techniques these days. This process is called 'interface jitter', and it is an intrinsic part of that kind of digital audio interface. ![]() The inherent capacitance within the cable reacts with those transitions and the result is small, but varying, time shifts of the transition point. The result is that the transitions depend on both the audio data and the clock data, so the transition rate varies. word clock distribution amplifier distributes a word clock BNC input signal to 6 word clock BNC outputs re-conditioned. It's those transitions that define the sample points.īy contrast, AES3, S/PDIF and ADAT all embed the clock pulses within the audio stream by using a type of modulation process. #Bnc word clock proBut the important point is that the periods between each transition from high to low (and vice versa) will remain absolutely consistent. The Micro Clock MKII is one of the best performing external word clocks in the pro audio market today. ![]() Cable losses will slow the transitions, so what falls out the end of the cable will probably be a little more rounded than what went in. The reason is that word clock is a really simple square-wave signal running at the sample rate. The Klotz World Clock Cable BNC 2m features flexible coaxial cables (stranded connectors) with high-precision characteristic wave impedance - premade with. Parallel distribution uses a BNC T-connector attached to the BNC word clock input of each synchronized digital device. Photo: Prism SoundĪSOS Technical Editor Hugh Robjohns replies: Theoretically, recovering the clock from a dedicated clock source via word clock should be easier and better - with less intrinsic interface jitter - than trying to extract an embedded clock from AES3, S/PDIF or ADAT interfaces. ![]() However, passing an AES3 signal down a capacitive cable distorts the waveshape and introduces a timing ambiguity called 'interface jitter'. If a clock signal is a perfect square wave, as shown here, clock timing will be jitter free. HOSA BNC59103 75 OHM COAX BNC WORDCLOCK SYNC CABLE This cable is designed for use in low-power video and RF applications. When clocking an audio interface using an external device, such as a stand‑alone mic preamp with A‑D conversion, is it better to use the dedicated word-clock (normally BNC) connectors, or will the clock signal be just as good coming down the S/PDIF, AES3 or ADAT cable that is carrying the audio signal? ![]()
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