I have done extensive A/B comparisons between equipment. Be it pre-amps, amps, DACS, etc.
My experience is to play a favorite song (say CD) at the volume you like. remove the CD and play a white noise CD and measure the DB level with a meter. Then swap the piece of equipment with the one you want to test. Again play the white noise CD and adjust the level to where it matches the level of the previous unit. Record both unit's levels so you know where to set them when listening.
Making sure the levels are matched before comparing is absolutely important.
Now that you have established the two levels, go for it.
Listen to the first unit with music you know. Then swap the new unit in. making sure to turn the amps off if swapping amps or mute pre-amps if swapping other stuff.
This has worked very well for me in making purchasing decisions.
enjoy
My experience is to play a favorite song (say CD) at the volume you like. remove the CD and play a white noise CD and measure the DB level with a meter. Then swap the piece of equipment with the one you want to test. Again play the white noise CD and adjust the level to where it matches the level of the previous unit. Record both unit's levels so you know where to set them when listening.
Making sure the levels are matched before comparing is absolutely important.
Now that you have established the two levels, go for it.
Listen to the first unit with music you know. Then swap the new unit in. making sure to turn the amps off if swapping amps or mute pre-amps if swapping other stuff.
This has worked very well for me in making purchasing decisions.
enjoy