D.D.S. means Direct Digital System. It is the technology which DA&T developed and implemented in the latest Q-series.
Under D.D.S., volume adjustment is all done in the digital domain and can avoid the distortions caused by traditional analog design.
The system is no longer bothered by manufacturing errors or degradations of analog potentiometers. When feeding Q-series with an analog signal, it will go through an input filter over 100khz to minimize phase shifts and then converted to a digital signal. Digital signals, either fed directly or the one converted from analog, are upsampled and processed at 32bit/352.8kHz to achieve ultra-high 130dB dynamic range with low distortions.D.D.S. also can prevent ground interferences and crosstalks. Preamp section is no longer needed in D.D.S., that means the gain can be significantly lower and less noises generated.
In short, D.D.S. is more than controlling volume digitally but aims to overcome the weakest point in the entire system and deliver high fidelity audio.
Check out the DA&T range that utilizes this technology.