Could you please explain the comment "not only is your
gain staging incorrect and reducing your s/n ratio, it also screws up the
gain being sent to aux sends."? Consider the following example.
Let's say you have a mic signal hitting the preamp with a
level of -40dBu, the noise floor is -100dBu and with the
trim set for 0 you have the
fader at -10 to get the desired
level. Using the 0 signal
level trim method you would thus add 40dB of
gain at the preamp to bring the signal levels out of the preamp to 0dBu which also raises the noise
level to -60dBu, then
attenuate those levels with the
fader by 10dB so that the signals post
fader are -10dBu and -70dBu respectively. With the
fader at 0 approach you add 10dB less
gain at the preamp but then apply no attenuation, thus the signal and noise levels are -10dBu and -70dBu out of the preamp and after the
fader. So both approaches seem to result in a -10dBu signal
level and 60dB of S/N after the
fader, however the second approach with the
fader at 0 seems to result in the same 60dB S/N (0/-60 versus -10/-70) but 10dB more
headroom (a -10dBu signal
level versus 0dBu signal
level) between the preamp and
fader. At higher input signal levels the
trim at 0 approach may indeed provide greater S/N, but that seems to not be relevant to mics while as long as having the preamp output at 0dBu results in the
fader being below 0 it seems that will always result in having less
headroom between the preamp output and
fader. So why is a method that provides greater S/N only for higher
line level signals where the S/N ratio is typically higher to start with and less
headroom through part of the signal chain for most signals inherently better?
As far as screwing up the
gain to the aux sends, I believe that the additional
headroom between the preamp and
channel fader can actually help with not screwing it up as you are typically combining multiple signals onto a single bus, meaning that if you start with all of the preamp outputs at 0dBu then you usually have a higher total
level, and thus less
headroom, than expected on any
pre-fade send buses. And on many consoles there is no way of monitoring those levels except perhaps to look at the output
level and factor in the master
send level setting. Having a
bit more
headroom on an aux bus does not seem to be a bad or even undesired thing.
So I'm not
clear how setting the
trim to provide a 0dBu
level actually provides better
gain structure or better S/N or how it is problematic for aux sends. Maybe you can explain it.
A less technical aspect is that if having the preamp output at 0 results in the faders being quite low then you are into a non-linear part of the
fader's operation where small movements make large differences, making it more difficult to have fine control, as well as having less attenuation available with the
fader all the way down. And I find that having a consistent starting
point for the faders really helps when you have to move from one
mixer to another, such as a BE using different
house systems, as trying to mix the same thing as always but with significantly different
fader settings can
throw you off. So can having to remember where faders were set to bring them back up after you have brought them all the way down.
I also do not understand why the indicators would be rendered "useless" by having the trims set lower. They are simply monitoring
level; the peak light still lights when the maximum input
level is reached, an XdBu
level signal is still reflected as an XdBu
level signal,
etc. Nothing has changed the indicators' functionality or use.
I am not advocating simply
lining up all the faders at 0 but rather setting them at levels that make sense for operation. If you have an input that you know needs 20dB more
level for a solo, then start with the
fader 20dB down from the nominal starting
point. However, don't get so tied into setting all the preamps for 0 that you find yourself not having enough useful operating range on a
fader or that you are
clipping an aux bus. The reality is that you may get the best result with some combination of or intermediate approach between the two extremes.
