What is the difference between a tube amplifier and a solid-state amplifier? Does the human ear prefer one over the other?
The only difference between a well-designed tube amplifier and a well-designed solid-state amplifier is the device doing the amplification. In fact, a vacuum tube and an metal-oxide-semiconductor field-effect-transistor or MOSFET are extremely similar in behavior, so that amplifiers built with the two devices can be extremely similar. If these amplifying devices are used properly in a good amplifier, that amplifier should only boost the power of its input signal and shouldn’t add anything that wasn’t present in the input signal. As a result, you shouldn’t be able to tell whether the audio amplifier you are listening to is based on tubes or on solid-state components.