The scale doesn't include a frequency number for the point where it cuts off. Is this an old DAC without oversampling or something like that? I'm not sure whether that would be audible or not. It's certainly marginal, but it's stone flat out to 10kHz and it looks like by the time the rolloff gets to -3dB, which is a general rule of thumb for audibility of a frequency imbalance with music, it's up to about 17kHz, which is above the range where there's much content in music. A modern DAC with oversampling really should be flat from 20 to 20, but a roll off like that is as close to the line of audibility/inaudibility as you can get. I would bet that someone could use that DAC every day to listen to music and never notice that rolloff.