Typo there, it should be "psycho-acoustic" bias.

And I should qualify my statement: differences between grille-on and grille-off are inaudible in blind tests using musical program material. You might be able to hear a slight difference using a full bandwidth pink-noise test signal, which is extremely critical and contains equal energy per octave across the musical spectrum. It's been some years since I've tried that.

Regards,
Alan

Alan Lofft,
Axiom Resident Expert (Retired)