"If you must Buy One - Buy Avalon"
It is particularly clean, but if you gain the input, you can get a very warm and almost gritty sound very nice for close mic Vocals and Acoustic instruments, if you want them saturated.
My personal favorite overall vocal/acoustic guitar pre-amp
It has the whole kit and caboodle... the only thing that I personally Love, but some people find annoying is it's compressor... the attack is a bit slow for certain applications... kick, etc... but for vocals and pretty much everything I need my main class a pre-amp for, it is more than fast enough.
The other features include a great EQ with several options and crystal clear breath. I have used it on everything... Bass, Bells, Choirs, Acoustic Guitars, Electric Guitars, Vocals, Percussion (bongos/shakers, etc)... I can't even tell you everything that the EQ has enhanced beyond my expectations.
The general Gain is best when used above +0 It is pristine at 0 and gets warmer the louder you gain the input.
I am a huge fan of this piece of gear, but the pots do go bad after a while, if there is abuse... I bought new just because of that... some friends that bought used were sad to hear the crackle of the pots... you can luck out and get one under warrantee, sometimes, though.
I have not ever needed any repairs on mine, but as I said... friends have, and the company was great about the quick and positive response.
I personally thing it's worth every penny... but it is pretty expensice, if you aren't needing the best.
The Wow Factor:
It is freaking hot.
I will never replace it.. but there are definitely other pre-amps that have very unique and different sounds.... I'm a fan of Manley, and it may be my next one.