There are a pair of 1/4" input/outputs and a pair of XLR input/outputs.
The are no traditional effects. I guess you can say that the Phase correction is an effect. This comes in handy when setting up your mic correctly.
Yes, it is rackable. Thats what its designed for.
This is all analog with all the parameters that you can edit on the face, so yeah, its very easy tweaking the sound.
The setup/configuration is fairly simple. I had not had much experience with tube preamps before, but the manual is actually quite helpful in guiding you. After I read it, I felt pretty confident on this guy and was able to get some really good sounds out of it.
Yes, it is transparent if thats what you are setting up to be. It also colors the sound and warms it up a bunch if you set up to do so also. The quality of the "Tube" sound (if thats what you are going for) is highly dependent on the quality of the tubes you put in it. It comes with a pair of cheap chinese tubes (i forget what brand) originally. I got online and bought a nice pair of Gold plated Tung sols and it made a world of difference. Very warm sound now and much more transparent than the original tubes.
What I like most about this unit is the very good quality sound you can get out of it with the Right tubes. Even with the right tubes, this thing didn't cost me more than $400. Thats not bad for a quality preamp.
What I didn't like...? Nothing really. When I got mine in the mail, one of the VU meter's Lights wasn't working. I called ART and they express mailed two new ones to me, free of charge and explained how to change it myself (they did say I could return it or have it serviced, but doing it myself was the quickest and easiest way). All good stuff to me.
I was shopping around for a Tube preamp for awhile on a budget, and this was by far the best I could find for the price.
The precision and quality of the sound is quite good for how much I spent on it. I used a really nice Avalon preamp in a studio a few years back. It was amazing, the sound was fantastic. I would have definitely bought an Avalon if I could afford it, but they are $2000 minimum. Other than that, I only read reviews to figure out which preamp to buy. I am happy to say that the ART Mpa is a pretty solid machine and I wasn't disappointed at all.
Yes, I would make the same choice being as it is that I can't afford an Avalon yet.