Recently picked up a Focusrite isa 110 preamp. Also have an ART tube preamp. Thought it might be fun to compare each and see if there were any differences. All comments are with a vintage SM57 used for testing.
No preamp - just ran an SM57 straight into the kemper for profiling. This sounded good, but was slightly dull on the high end. not saying it was unusable, just not as bright as the other two.
ART Tube Preamp - a few more low mids, thickest sounding, little more high end than no preamp. This would be nice for some amps like marshalls when you would want a really thick full tone.
Focusrite asa 110 - Brighter than no preamp, and more clarity than the ART. more highs but not harsh, it seems to jump out of a mix a little more. Where the ART is thicker and fuller, the Focusrite has more detail and well, focus.
I'll have sound clips this weekend. My personal favorite is the Focusrite because it just sounds better to my ears. Reminds me of running a mastering plugin - just has a little more of everything and sounds bigger.
ART is great sounding for the $. Heck, no preamp sounds good too. It's not a night and day comparison - you'll never hear a profile without a preamp and then the Focusrite, and think the Focusrite was a different amp or anything... but there is a small difference.
Clips in a few days. Also will have some new profiles up, Mesa Maverick! ;0
Pete