A common issue with connecting modern sources is the output level they expect all components to accept.  Since the age of the CD player, most modern sources output around 2 volts, while both power and integrated amplifiers typically have a much lower input sensitivity of between 100-500mV.  The result being you have limited range of control on the volume pot and you are operating in the lower portion of a volume controls range, which is typically where channel imbalances occur.   I found myself in this exact situation when using my Audio-GD Compass...