This bass preamp turns to me on 18 volt. Electronics (active) is very effective. there are 5 knobs for the following settings: volume, micro balance, bass, treble and medium on which there is a further adjustment through the push-pull. It is very comprehensive and rendering is very good. With that it's impossible not to find one's for you.
The preamp is quite expensive even import. I paid almost 200 euros but I do not regret anything, it helps to make the best microphones (also of Bartolini)