Building on the huge success of the award winning DAC64 the QDB76 is now able to take digital to
analogue conversion to a new level with improvements in performance and sound reproduction not
seen anywhere else. Added to this a unique Bluetooth digital audio receiver has been designed to
enhance connectivity so that you can stream high quality music wirelessly from a Bluetooth enable
phone, PDA or personal computer.
The digital design of the QBD 76 from digital input, to the DAC outputs, is designed using the latest
generation of field programmable gate array devices (FPGA), now with 1.25 million gates. The FPGA
handles the switching of SPDIF inputs, all digital SPDIF decoding, digital PLL, RAM buffer
controller, WTA filtering, and the 5
th
generation Pulse Array DAC. All of these functional blocks are
designed at the gate level, for maximum performance. The QBD 76 features state of the art
improvements to the Pulse Array DAC, in particular the noise shaper architecture. Considerable work
has been done to improve this aspect of Pulse Array, and new noise shaper has been developed, with
the specific aim of reducing noise. Amongst other improvements the 5
th
generation Pulse Array now
has 8
th
order noise shaping (the highest order of noise shaping of any known DAC), and 2608 times
oversampling and digital filtering. A new digtal PLL has been developed using a highly accurate
115MHz clock. Data related jitter is completely removed from the source, and you are left with just
random master clock jitter of less than 3pS cycle to cycle. The subjective result is that the sound quality
is now improved to a level similar to when the RAM buffer is used.
Usability has been improved with the addition of a display and control via a microcontroller circuit.
Input selection, phase and RAM buffer settings can all be changed using three buttons on the top panel.
Configuration is clearly visible via the magnified display. The number of digital inputs has been
increased to include two coax, two AES and two optical inputs as standard, but now the addition of a
USB input enables connection to a personal computer so music can be streamed directly.
However the most important and major technical advance is the Bluetooth audio input. Modern phones,
personal digital assistants and personal computers now have the ability to transmit high quality audio
using the Bluetooth Advanced Audio Distribution Profile or A2DP for short. Using a custom designed
Bluetooth receiver we have been able to extract the digital audio information and input this directly
into our DAC technology. Unlike the analogue audio outputs seen from other Bluetooth devices this
gives us much better performance and enables CD like transfer of music from the Bluetooth device.
With its ground breaking sound performance and features the QDB76 defines the future of digital
music playback.
