None. Why use a linestage if you don't need one? If you only have one high level source/cdp look for a cdp with an analog volume control like the Resolution Audio 55 and Audio Aero Capitole. You will also eliminate one interconnect saving money and improving the sound. Yes, one less interconnect makes a big difference. Another way, but maybe not as good, is to look for an amp with an attenuator built-in or find someone who can install an attenuator into your existing amp. I really believe that an active linestage (only) is just another way for the manufacturer to sell another component.