Q: "How do I emulate an outboard compressor in Pro Tools?"

Question from a Audio Masterclass visitor...

"How do I emulate an outboard compressor in Pro Tools HD3. We are in the process of obtaining an Avalon or a Neve preamp, but in the meantime, I would like to compress vocals BEFORE they are written to tracks. I do a lot of R&B recording, with many many tracks, and the process of compressing after and controlling dynamics becomes increasingly challenging. Is there a way to place one on a send or bus or something? Thanks in advance... - Southern Prince"

I had to read that one twice. How do you emulate an outboard compressor? Well, you just buy an outboard compressor emulator plug-in. Simple as that, isn't it?

But not quite. The question asks about performing compression before recording. So that the recorded track is compressed. The usual procedure in Pro Tools is to compress the signal as it is played back, which is a different way of working.

I'm not going to talk about the pros and cons of each method here. That would be a whole discussion in itself. But let's have a look at how they are both done.

Here's the standard method of compression. There isn't much too it, just a compressor plug-in inserted into a track. The signal on the disk is uncompressed and it is compressed as it is played back. (Click the images for larger versions.)

Now, if you want to compress while you record, the setup is rather more complex.

Here, the output of the microphone is routed to an auxiliary track, the output of which is not recorded. The compressor is inserted into this track

The output of the auxiliary input is routed to Bus 1. Pro Tools LE, which is shown here, has 32 buses. More than you would ever need in most circumstances.

A new track is created where the input is taken from Bus 1. The compressed signal from the auxiliary track is recorded onto this track.

Job done!