Chord Hugo 2 headphone amp/DAC Sidebar

The WTA Filter

Under the Hugo 2’s bonnet, Robert Watts’ WTA (Watts Transient Aligned) high-rate digital filter, which has no fewer than 49,152 taps (coefficients), runs on a single Xilinx Artix-7 processor alongside a ten-element version of his proprietary Pulse Array bitstream DAC. These ten elements (per channel) are visible as the cluster of chip components in the centre of the ‘inside shot’ on the second page of the main review. There are no off-the-shelf upsampling/DAC chips in here...

Watts’ Pulse Array solution first appeared in Chord’s DAC64 model some 18 years ago and has been instrumental in driving the success of Chord’s digital products ever since. This iteration features a two-stage filter (16x followed by 256x, with 7th-order noise-shaping) in addition to a user-selectable HF filter acting above 40kHz. Intriguingly, Watts maintains that it’s not the extended response provided by high sampling rates that improves sound quality, rather the improved timing of transients. Watts’ DAC is able to handle DSD data natively, without conversion to PCM, although the proprietary nature of the WTA filter means it will never be adapted to accommodate the likes of MQA. PM

Chord Electronics Ltd
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