I own both of these pedals and highly suggest both. They are somewhat similar but different enough to justify me keeping both.
First is the Exotic BB Preamp,,this pedal is probably about the best preamp/overdrive out there,, it doesnt color your sound,,it offers higher gain than the Ibanez ts808 for comparison,,it has both a treble and bass knob so no mid range hump and is true bypass if that matters to you.
This pedal is very close to a true tube amp sound. I use it mainly as an overdrive on top of my amps distortion which gives it a fuller, smoother, gainier, and more sustain without coloring my amps sound. Look for the bb in other threads on this board and you will see many feel this is one of the best out there.
The other pedal is a MI Audio blues pro. This pedal is very, very similar in sound to the BB only it has more compression in it which I find tightens up the sound even more so than the BB. I also find it to be much quieter while using it as an OD ontop of my amps gain. Both are very quiet used alone on your clean channel though and both are very sweet all alone,pedals only,,very tube like sounding.
The blues pro only has one tone knob but it has a wide range of available sound unlike the ts808's tone knob.
The blues pro also has a toggle switch on top that offers a fuzz mode which I really cant say ive ever even tried so I cant say anything about that. This pedal is also true bypass. Honestly I love both of these pedals but for the money I think the MI Audio wins hands down.
http://www.prosoundcommunications.com/english/xotic/effects/bb_preamp/index.html
http://www.miaudio.com/BP1.htm
