Wow, not very complete answers here. A buffer, be it tube, or transistor, presents the driving component with a very high impedance, making it super easy to drive, particularly for the IC based output stages of inexpensive CD players and DVD players. In addition, it has a very low output impedance, which makes it very good at driving the input of the receiving component, as well as minimizing the effects of long interconnect runs. I beleve that the MF has one db of gain, which is incidental, but it will make it a tich louder. As mentioned, there will be a change in the distortion spectra, though these are generally pretty low distortion devices. Any active device, and the extra cable required to implement it will change the sound.