We last ran a comprehensive USB cable group test over six years ago [HFN Jul '13 and '14] with Chord's entry-level SilverPlus coming top-of-the-heap and remaining in residence ever since as our cable of choice. The intervening period has seen the SilverPlus morph into the current entry-level C-series while the costlier Signature 'Tuned Aray' USB cable became the template for Chord's more recent, intermediate Epic USB model. And, at £400 for a terminated 1 m set (£ 160 per additional metre), the new Epic USB is no costlier than its Signature forefather in 2014. So, the Epic USB employs a similar set of four PTFE-insulated, silver-plated copper conductors for the +5V line and ground plus the differential data pair, which are also separately shielded. This geometry deviates slightly from the USB standard (you'll notice that few 'audio USB' cables carry the official USB trident motif), but limited overshoot on the waveshape and a fast 9.6nsec risetime [see black waveform, Graph below] suggest its characteristic impedance is not too far under the 90ohm standard, at least at these data rates and frequency. Note that a 5m length of Epic USB has a slightly reduced bandwidth but exactly the same edge risetime [red trace]. A 2m length may well prove optimum.
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