The idea behind the buffer is that the input music stream is stored there and clocked out accurately, so reducing the levels of jitter. One of them toggles through the inputs – the smaller circular window shows an internal display that indicates the input selected – while the others set signal polarity and buffer level. Take a look at the QBD76 HDSD’s top panel and there are three control buttons on the left of the large, colourfully lit porthole.
Instead, its engineers have used large-scale programmable logic gate arrays – 1.25 million in this case – to run proprietary software that does everything from the switching of S/PDIF inputs to the actual digital conversion and filtering. Unlike many rival designs, Chord’s top-end converters have long eschewed mass-produced, off-the-shelf DAC chips the company feels these restrict performance. This is down to the machining of the casework around the socket and means that cables with bulky plug designs don’t always sit properly. On a practical level we’ve found the optical input a mite fussy about the design of plug it will accept. If not, as is probably the case, the upper resolution limit for both input types (used individually) is 24-bit/96kHz. If your digital transport has twin outputs for optical and AES/EBU – rare, admittedly – these can be used to deliver a 192kHz music stream. These make a nice, secure and electrically matched connection, potentially giving a better performance than the more commonly used RCA alternative. The co-axial connection uses BNC sockets. A DAC with two USB inputs is unusual, but could be very useful for some.Īlongside the USBs there’s the usual array of optical, co-axial and AES/EBU inputs. This can be used for files up to 48kHz, but Chord sees this input being used predominantly for playing uncompressed CD (16-bit/44.1kHz) rips. The QBD76 HDSD also retains the basic USB connection of the original.
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