There is no neutral.
Surely there is no absolute neutral. But some electronics approach the straight wire with gain (Stewart Hegeman expression) better than others. IMO Lamm is not one of those.
In my limited experience, the old Cello Audio Pallette with the equalizer switched off was one of the more neutral preamplfiers I used. A good friend owned the Cello Audio Suite and it was also very neutral. At that time I was listening mostly to Quad ESL63.
I still regret having sold the Audio Palette.