Scaling brushes but keeping resolution

Hi, I was wondering if anyone can help. 

I'm using brushes like pencil's and paint brushes, and I'd like to scale them. When you scale them normally, i.e. with the brush size setting it breaks the look. What I want is as though you had scanned a drawing in at a higher resolution, so the brush still looks the same, it's just bigger.

I'm assuming this is just a limitation of the way photoshop makes brushes and brushes only really work at the size they were made? This is a real shame, cause so many brushes seem to made for a lower resolution than I work at.

Here's an example of what I mean:

Thanks