every electronic amplifier or recorder or microphone 'colors' the sound in some way.
anyone who claims that their gadget does not color the sound is either ignorant, lying, or has added tons of negative feedback to 'mathematically' remove the artifacts so that they can publish low distortion specs..
tube stuff sounds great, realistic and keeps the magic of performance, because of the way it works..Most hi-end pro tube stuff that is..
cheap tube stuff with bad power supplies, cheap tubes and transformers is what gave tubes a bad name, although the vacuum tube is a superior active component for audio regarding bandwidth, noise, current vs. voltage, linearity etc.
transistor stuff ranges from brittle and harsh to clean and punchy.. with some discrete stuff sounding good, some custom made desks sounding excellent (german broadcast F.E.) and rivalling tubes, but with more punch.
op-amps and other cheap IC circuits are usually a dissapointment audio-wise...but they are good for DC voltage calculations..