Many tube amplifiers have a sound described as "warm," "tubey," or "round".  This sound can be very nice to listen to. However, it is the output transformers that produce the "warmth" or the tone of the sound, and it is actually a type of distortion, though pleasant.

The downside is the detail of the music can be lost in the "warmth." There is no doubt that many people love the warmth of what they think is the tube, but is actually the transformer.

ZOTL amplifiers do not have the thicker, warm tone that many tube amplifiers have. They still have the liquidity and linearity of tubes, but without a transformer's tone.

ZOTL amplification achieves neutral accuracy without coloration. This achievement is supported both by listening and through measurement.

Switching immediately from other tube amplifiers (and solid-state amplifiers designed to be warmer) to a ZOTL amplifier can often feel like something has been lost. What is actually happening is more akin to adjusting the focus of a lens: an increase in clarity accompanies a reduction of haze. While haze can feel like "body" or "weight" that is no longer there, as you adjust to the ZOTL amplifier you realize you are hearing the more accurate weight and body of what you are listening to, and the consistency in performance over varying impedances will allow you to experience this accuracy throughout the frequency spectrum with many different speakers. 

ZOTL amplification's neutrality is also transparency. As source components increase in performance, ZOTL amps continue to reflect this, scaling up indefinitely.