What Moon told you about your DAC handling clocking chores regardless of the cable type used from the source is increasingly the case now and was referenced in a recent post about streamers.
I am trying out an enhanced version of ai right now (Sonnet 4.6), and this is what it had to say. Past dogma on this subject is being replaced by a new reality in many modern DACs.
Question: Does the source device clock always override the clock in the DAC when using a spdif cable?
Answer: No, not always — it depends on the DAC’s design and its clocking architecture. Here’s how it works:
Typical S/PDIF behavior (source clock dominates)
In a standard S/PDIF connection, the clock is embedded in the bitstream itself. The receiving DAC must lock its internal clock to this incoming signal using a Phase-Locked Loop (PLL). In this common scenario, yes — the source device’s clock effectively governs the timing, and any jitter or instability in the source clock gets passed along to the DAC. This is a well-known weakness of S/PDIF.
When the DAC can assert its own clock
Some DACs are designed to minimize or eliminate source clock dependency:
∙ Asynchronous reclocking / reclockers: Some DACs have a high-quality internal oscillator and a buffer that accepts the incoming S/PDIF stream, then re-reads the data using the DAC’s own master clock. This effectively breaks the dependency on the source clock and can dramatically reduce jitter.
∙ Large jitter rejection / FIFO buffering: Some DAC designs use a large FIFO (first-in, first-out) buffer to decouple the input clock from the output clock. The data comes in governed by the source, but it gets read out by the DAC’s own clock. This is more common in professional gear.
∙ External word clock inputs: Some higher-end DACs have a word clock input, allowing a dedicated master clock to govern everything, completely overriding the S/PDIF clock.
The key contrast with USB
This is one reason why asynchronous USB audio is often considered superior to S/PDIF — in async USB mode, the DAC explicitly pulls data at its own clock rate, making the DAC the unambiguous master. S/PDIF has no equivalent standard mechanism for this, so it requires the workarounds above.
In short, whether the source clock “wins” depends on how sophisticated the DAC’s clocking circuitry is. A basic DAC will be at the mercy of the source; a well-designed one can largely sidestep it.
kn