I've never heard a transparent instrument amplifier. My hi-fi stereo features a single-ended tube amplifier with nothing in the circuit but a volume pot. It feeds a pair of single driver, crossover-less speakers with a near flat frequency response. Now, THAT is transparent or at least close to it. It takes some getting used to and it's not for everyone. I will say, of all my bass amps I've preferred SWR and Markbass the most, which are brands that people consider "transparent" so... I'd imagine the most transparent sound would be to feed the board with a basic DI.