My colleague at the studio was about to record an artist that I have been working with a lot during the years. So he asked me if there was anything he needed to know or if I had some tips for his upcoming recording session. One of the things I told him was that I used to achieve great results with the Avalon preamp with some smooth compression. My colleague told me that he didn't use outboard gear because he felt like if you screw up there is no way to fix it. He prefered to fix things later in the mix.
What I Like
Personally I like to use a bit of compression on the way in. I always want my recordings to sound as finished as possible in the recording stage and I like to have more control of my input signal. Even though, I fully understand the no compression during recording philosophy. Nowadays we don't have to worry that much about headroom. Back in the day, you were kind of forced to compress so as to get as much signal to tape as possible just because the headroom was much lower back then.
What About The Screw Up Potential?
Of course you need to keep in mind that all the adjustments that you are making to your signal on the way in is like getting a tattoo. You are stuck with it. You should be certain of what you are doing, otherwise you will regret it. I remember when I were studying audio engineering I had access to a really nice studio with a lot of high-end outboard gear. Combine too many 1176 and LA2s with a young gear-horney unexperienced audio engineer with the philosophy "more is better". But my view is that mistakes are good as long as you learn from them.
Plugin Or Hardware
If I have access to a good outboard compressor I probably will go for that. But in my opinion the UAD plugins are really versatile and sound extremely good. If you don't have access to any outboard gear but can get your hands on the Apollo, and some UAD plug-ins and you will be fine.
I don't like to tell anyone which settings to use, because in the end it's all about what you're hearing. But this can be a good starting point when using compression during recording.
Ratio - 2:1 Low ratios allows for less compression.
High Threshold – Set the threshold to where the signal is just barely crossing it. If the compressor is constantly compressing, the threshold is too low. Raise it up until you only get a little bit of compression.
Slow Attack – Keep the attack slow (50-100 ms) prevents from affecting the transients of the signal too drastically.
Smooth Release – Set the release around the same as the attack. If the release is too fast, the compression becomes more noticeable.