Question

the preamp is a blue tube  2 CHANNEL mic /instrument  unit. When I use a condenser mic with 48 v power. I have to turn the gain up to 45 to get a decent. level. On a dynamic mic. I have to turn it up to max.  Is this Normal or is there something wrong with the unit/

Answer 1

Each model interface has a mic gain range and varies by model. Some have more gain than others. Using 3/4 for a condenser mic is not unusual and you'll also need to use the 48 v switch.
Dynamic mics take much more gain than most interfaces provide and you shouldn't use the 48v power on a dynamic mic. An inline mic booster can used on a dynamic mic for an additional 15 db or so of gain.
Hope this helps
EJ

Answer 2

To add what EJ already provided, microphones all have their own sensitivity and will need a different amount of gain from the pre amp.

Ribbon microphones need the most, then dynamic and then tube and condensors.

As long as you get enough signal to work with, I wouldn't try to boost the signal any more than necessary as you can more cleanly boost it digitally.

Steven