By running the channels a little lower than 0VU when you PFL on the mixer the advantages in less distortion offset the relatively low signal at the A/D(input on recorder).Some transients will actually be higher than the VU/Peak meter will indicate.
0 VU is normally aligned to be about +4dbu out of the mixer, which is probably around 18 - 20db below the desks maximum output anyway.
Further the VU is NOT a peak reading device, so there will of course be higher peaks, but probably not 18db higher peaks! Now there are some meters used on cheap gear that are (despite the labelling) NOT VU as they have completely the wrong ballistics (possibly and scale markings), but 0VU should be WAY below clipping for any sane analogue desk.
Quote:-18dbFS = 0VU = +4dbu is one of the two standards for this, but if you have aligned as above, 0VU will be -18dbFS, and digital full scale will be +22dbu (which is reasonable given balanced connections and a sane desk design, and is way past the top of the VU scale).
I often track at -18dBFS and this leaves plenty of analogue and digital headroom.
It surprises me when I see LED VU meters on live desk channels running at +15VU (1 LED before max) which occasionally ends up briefly clipping an A/D and probably has a sharp rise in analogue opamp distortion as the device reaches is operational limits.
If it is an LED meter, it probably is not a VU (in most cases), and is most likely much closer to peak reading then a true VU (it may even be peak reading), which probably explains why the user is getting away with that.
I would also note that some desks (and especially some preamps) distort when driven hard in musically useful ways (Not that I would class a Mackie in that category), so hammering the channel can be a useful trick.
Ref the 16 Vs 24 bit thing, there is NO extra resolution, just a lower noise floor. Both systems are perfectly linear (If implemented correctly (Not always a given)), the ONLY advantage of 24 bit an increase in available dynamic range, nothing else (That is reason enough to use it in production).
Audiophiles use phono leads because they are unbalanced people!