to properly answer the original poster's question...
you should be tracking a DI to something much higher than -18 dbFS... why? because if you're not intending to use this signal DRY, then you intend to put it through a processor..
that processor is going to have its own requirements. For instance, pod farm requires your guitar signal to be "mostly in the green/yellow range", yellow being fairly hot as indicated on the meters inside the plugin.
the people telling you that tracking at -18 dbFS are correct, you should be doing that for things like DRUMS, BASS, and VOCALS. but not for a DIRECT INPUT SIGNAL that is intended to only go straight into a processor.
and because I have a lot of lurkers who will ask the fuck out of me about this, no i don't follow the -18 dbfs rule
Well you could track at -18 to get the cleanest possible DI signal and then use a gain/trim plugin in your DAW to boost the level a bit to get the best level for your amp sim. Potentially you're going to have a slightly worse noise floor compared to tracking hotter, but really when you're distorting your guitar tracks anyway I don't think it would make much, if any difference.
furthermore. someone could tell you exact compressor settings to a chris lord alge mix, but it wouldnt mean shit if your input gain wasn't the same as the mix. in otherwords, everything in mixing, volume, and audio is relative.
Totally, in that case it's all about knowing what gain reduction you're aiming for and adjusting the threshold to suit the source material.
I know this topic has been covered to death, but for some reason I never really looked into the discussions until now. I'm using a Firewire 410 and the Behringer VAMP Pro. I always try to get my peak guitar levels at around -3db when tracking and I don't use the pad function on the Firewire when doing so. I guess I should now? Now that I've finally read some information on this topic, I'm more confused than ever.
I don't see what's so confusing.
Analogue gear, like preamps, converters etc are designed to work best at around 0Vu. By tracking hot you are making the analogue gear work outside of it's optimum range, and adding unnecessary distortion to your signal.
By aiming for an average level of -18dBfs in your DAW, you're analogue components should be working at about 0Vu (depending on how your converter is calibrated) so you will be getting low noise and low distortion.
Simples!
Tracking as hot as possible without clipping is something that came from the days of recording in 16 bit, where you had to deal with a higher noise floor and more limited dynamic range compared to modern 24 bit systems.
It's also much faster to say "track as hot as possible without clipping" than it is to get into a in depth discussion about analogue vs digital, noise floors, total harmonic distortion etc etc. So this is the advice that has been handed down to recording hobbyists in the instruction manuals of consumer audio gear.
Unfortunately with the new Mbox's having built in soft clippers it seems this is a trend that is set to continue, apparently adding a feature that isn't particularly necessary is better business practice than educating your customers in how to use your product properly.
