I have another take on this, a little different from above. While what he said is technically accurate, it is a balancing act. If you're using a *really* low-end audio IF, stay ITB. In my opinion, if your converters are mediocre or better, OTB is viable. You will lose a little fidelity on the round trip, but you have to judge the following:
- is it *actually* audible/noticeable. Be honest here. If you have a pretty decent monitoring setup and you still can not hear the difference, the VAST majority of anyone who hears your mixes will never be able to tell.
- If you do notice 'something', is it enough to offset the benefits of OTB mixing with good outboard gear.
I mix using a combo. I have mediocre converters and a decent monitoring setup. I notice a *slight* reduction in fidelity after an DAAD round-trip, but not nearly enough to stop me. I have some good outboard compressors, EQs, reverbs/FX, etc. Sometimes I just REALLY want the sound from my real 1176LN, instead of my UAD-1 copy.
One thing that I ALWAYS get with OTB that is extremely difficult and usually imposible ITB is depth. The difference is amazingly drastic, IMO. The SSL Duende actually does a really good job of imparting an OTB sound to the tracks it touches. It, alone has kept me ITB a lot of times that I would have gone out. If I buy a second one, who knows??
Anyhow, I have a lot of UAD and SSL plugs that I love and use. They are valuable to my mixes. Some time in the not-too-distant future, I'll invest an ass-load of money in high-end converters. At that point, OTB will not be a sacrifice. But, with proper gain staging and PROPERLY RECORDED SOURCE TRACKS (I follow the '-12 to -8 for digital' philosophy), I really do not suffer much loss at all. Also, if I know I will be doing a lot of OTB on a song, I will record at 96k. It just makes sense to me to have the extra information available in the files if I'm going to be doing a lot of destructive editing.
At any rate, to answer your question: I would go with a really good 2bus comp. Especially if this comp is versatile enough to use on other tracks...that is to say, something you could run a few things through individually before you strapped it to the Master Bus. A good 'glue' compressor can make a HUGE difference on a mix and is, IMO a great place to start when going OTB.
You might also think about some good tube amps with line drivers to run the master bus signal through before/after it hits the compressor. I do this all of the time to add character (I WONT say 'warmth'
) to my mix...just watch your gain staging carefully!
Good Luck!