Melodeath
Moonbow
It is possible to connect an external preamp to the Pro 40 right?
Yes, but you cannot bypass the pres, as far as I'm aware (judging based on the LS56), whereas you can on the Profire 2626. It's up to you whether this matters. Personally, I use my Liquid Saffire 56 all the time, and only connect my Profire 2626 through ADAT if I need more inputs.
Explanation: on the Profire, you can go external pre>line in>A/D converter
On the Saffire, it goes external pre>line in>preamp>A/D converter