Why you should not send compressed mixes to your mastering engineer...
You'll see in videos and in writing a lot about the 'glue' a buss compressor can provide on your master buss of Logic/ProTools/Ableton and so on. It's true!
Don't get me wrong, the power a nice and complimentary compressor or limiter can provide on the output of your audio is what mastering is partly all about after all. Whilst I'd not tell you not to mix with one in the chain, although I believe it could cloud your judgement if the settings were wrong at all. Consider the analogy. Would you send your car to your local mechanic for a service and prepare the car by unscrewing the covers that hold in the air filter, or start to unscrew the oil filter for them? No. Presumably you pay the mechanic for their skill and ability to see whether that filter, or anything else around your car is not working. It is not that you're incapable of wielding a screwdriver - of course you are, but it's the experience and skill you pay for. It is exactly the same in mastering. What you think sounds like glue, may very well be that, and be good, but two things are at work here. The first is not that it is bad, but a mastering engineer will be able to do better with their equipment and skill. Remember all a mastering engineer does is play with compression and EQ of this sort most of every day! The second is what I call 'Demo Fever' and others call 'Demoitus'. Essentially Demo Fever is where a band or artist is so happy listening to the demo they did years ago in their home studio, that when they've done the professionally produced version in the major studios, they're disappointed. Subconsciously they've become attached to 'that' sound, rather than the better one. An emotional attachment. So what should you do? When you're about to submit to your mastering engineer, either ask them what they'd want, or send them what I'd prefer which is :
A clean master - without your buss compression or EQ please
Your buss-compressed and EQ'd master - this can be used as a guide to understand what you like and why. A ball park for us if you like.
Better still, bring you mastering engineer in earlier for Mix Advice, so you can discuss these issues with them long before the mastering session.