It seems many people want to make up the gain on the source side when really you are better off to raise the gain in the DAW. If you are having trouble hearing your vocals, turn the other parts of the mix down, turn the master up or turn up the monitors. Just don't try to make it all up on the source side. Source side you just want a clean signal in, it doesn't have to be at full gain.
This is a decent point to consider, especially when recording at 24bit, but you have to be careful. There are several things to consider:
1) There is noise entering
the system before the mic pre/mixer. The ambient (
acoustic) room noise, the microphone's self-noise, and any noise picked up in the cable will be at a given level relative to the signal no matter where the downstream gain comes from. The only way to change this is basically to make the desired signal louder at the mic itself.
B) All mic pre circuits have a basic noise floor. They will add some minimum amount of noise even with gain all the way down. Sometimes this is loud enough to mask any noise that the gain circuit might add, to where you are actually better off adding gain to get your signal back some of its dynamic range before you go to digital. Some preamps are actually worse in terms of S/N ratio at the bottom side of their gain knobs.
III) The noise floor in the digital
world is extremely low, but it does exist, and it does come up even when you add digital gain. Digital gain is clean in that it is (can be) exactly linear. It is quiet in that the code that applies the gain doesn't add any of its own noise. But even when your noise floor is at -144dbfs, if your signal is peaking at -60db, you've only really got 84db of range there.
The point being that if you really want the best
performance out of your system, you have to test your system.
Anyway, the number one thing that is guaranfuckingteed to improve your S/N ratio is to make the S louder at the diaphragm. Turn the amp up or sing louder or move the mic closer. That always helps.