"Sticking with its policy of upgradability Ayre has been upgrading QB-9 DACs to the QB-9 DSD version for $500, the same as the price difference between the new and old model. As the name changed to QB-9 DSD implies, the sound quality improvement to this DAC is well worth the price of the upgrade. The QB-9 DSD is a completely different DAC from the previous generation of the QB-9. Adding the letters DSD to the QB-9 name is a bit misleading because this upgrade is much more about everything else inside the DAC than it is about the ability to play DSD material. Ayre has elevated the QB-9 to arguably the best sounding USB only DAC in its price range."