Well my quest to try the new line of Mesa Boogie overdrives has been met with disappointment. After trying the Flux Drive and the Throttle Box for a while in store, using a Thunderbird, a Precision, a Jazz and a Gibson RD I was only able to find a few settings on each that I liked.
Both seemed to function as more of a boost than an overdrive, you really need to crank them to get anything resembling drive. The biggest problem is that when they are engaged there is a big drop of low end, even with the help of the bass control. All of the dials seemed to do very little until they were past the 75% mark, where they finally started to do something, unfortunately they were both quite messy sounding ODs, quite woolly and quite a loss of definition in the notes.
There was nothing I could do about the loss of low end, with the "bass" dial at 12 o'clock there was still a big cut, moving it up to about 80% brought some bass back in but it was very boomy and ruined the drive sound. The treble control was fairly unresponsive compared to many other pedals, at 12 o'clock it was ok, but anything past that point was very abrasive and difficult to listen to (IMO of course). The only dial on either that did it's job well was the output volume, which it has loads of, this thing can get absurdly loud. Of the two I'd say the Throttle Box was the better, but not by much.
Overall I'd give both of these a 4/10 on bass guitar. I will return to the shop in a few days and try the other two, the place was incredibly busy today and after testing the two for just over an hour I couldn't stand the crowds and left.