I just got an HP60 headphone amp and the first two channels are significantly lower. I just went from input to input with the same pair of headphones and 12 oclock on 3-6 are about the same as 3 oclock on 1 and 2. Is this a known issue or is something wrong? The last channel is also noisy but I had read somewhere that is because of its proximity to the power supply so was expecting. I honestly only needed 5 inputs so I wasn't concerned about that, but the volume on the two channels is concerning. Does anyone have one of these and can tell me this is not typical so I know if I should return it? Thanks!