What are the differences between recording studios and mastering studios?
There is a reason why the best mastering studios are separate from recording studios. Your typical mixing room is not optimally acoustically designed as you have big consoles and racks that get in the way and cause problems. Since mastering engineers as generally considered specialists their gear choices also tend to me much more personal then recording studios which need name brand equipment like ProTools and Genelecs to impress clients. In general you should be wary when a recording studio offers “in house mastering”, because oftentimes they just throw some plugins on your songs while listening to them on the same speakers they were mixed on. Unless the studio has a separate mastering room, such “in house mastering” is probably only a marketing tool to get more business.