The Audio Note (UK) M3 Line Pre Amplifier has been specifically engineered for sonic performance rather than technical specification, and fulfills all Audio Note (UK) Level 3 criteria:
*Pure Class A operation
*Zero negative feedback
*Single Ended circuit topology
*Valve rectification
*Materials and component quality

It is well known that the accurate reproduction of music, not just sound, requires the purity of the incoming signal to be preserved. It is therefore not difficult to conclude that, in order to achieve this goal and to retain the musicality of the original performance, the complexity of the circuitry itself must be kept to a minimum. In response to this, the M3 Pre Amplifier uses a single-ended, zero feedback circuit topology. This is simply the most linear design possible, demanding pure Class A valve operation and removing the need for a phase splitter, which introduces unnecessary crossover distortion.

https://www.dagogo.com/audio-note-m3-preamplifier-review/