If you’re not a professional producer/mix engineer then chances are your mixes could do with improvement before going forward to the mastering stage. Do not underestimate the difference mix tweaks can have on a track. ‘Bigger’, ‘brighter’, ‘bassier’, ‘punchier’ ‘more depth and separation’ are just some of the adjectives used to describe the results when combined with an analogue(/digital) master. Every project will have different requirements so get in contact first.
If the mix is generally okay but lacks something overall, stem mastering could be the answer. Mediocre audio interfaces, poorly recorded audio and digital summing can often sound SO much better when the mastering process is applied to one stem at a time and the parts are brought back together for a final pass in the analogue domain. Drop us a line if you want to discuss this option further.