There are basically 2 approaches that would affect the volume output of the A30 other than the volume knob itself. First is to use the Balanced inputs from a balanced source/DAC. you essentially double the input voltage over the std. RCA inputs by using balanced. The second is to use the gain switch on the front. Use the medium or high switch settings. If neither of those approaches yield expected volume levels then you need to look at your source device(s) whether it is a preamp, DAC or computer. Any of those may have their own volume controls that may be limiting the final output levels. If none of these suggestions provide a good result then you have to consider a faulty A30 amp. Always turn the volume knob of the amp to a lower setting while you adjust other sources in front of the amp. You don't want a surprise volume blast that could impact speakers or headphones then make gradual adjustments to the volume knob to see if the change made elsewhere has affected the sound level.