Electro-Harmonix Bass Metaphors: This pedal was designed to compete with Tech21's Sansamp BDDI product line, in that it combines an EQ, a variable distortion, blending of the amount of effect, an XLR DI out, and the ability to be used as either an effect pedal or a preamp. It also features a compressor, which is why it's here of course.
The compressor seems to me to be identical to their reissue version of the Soul Preacher. It's very noisy, and it squashes heavily. It seems to choke the low end a bit, which you have to compensate by boosting the bass EQ knob. There's only one external control for the comp: an on/bypass toggle switch. There are two trim pots inside which allow you to adjust the compression. If you are going to turn them, be sure to mark their original position first! It seems like the pot nearest the wall of the box controls the make-up gain, and the pot nearest to the XLR jack controls the threshold. I got the best results (to my ears) by turning the threshold pot counterclockwise to about 10:00 (with the "legs" of the pot at 6:00). The factory setting of the gain pot is actually just about right, between 12:30 and 1:00. Adjusting those, and trying various EQ combinations, I was able to get some sounds and actions that were pretty decent; but in even the best of those cases, it never sounded as good as when I switched the compressor off.
The other functions of this pedal are OK. Without the comp, it has almost no noise, and the low end is fine. The DI output is clean and strong. The "dry" knob allows you to blend in your clean un-effected signal in with the distorted/EQ'ed signal. The distortion has a useful and versatile range, from softer and more overdrive-like at one end, to harsher and spittier at the other. It's not the best bass distortion around, but it's really not so bad, especially at the lower settings. Also, one useful feature is that as a preamp, this unit is capable of driving a power amp quite well.
The EQ has an interesting, fat sound; but using it is not easy or intuitive, and I had a hard time finding settings I liked. It is not a typical two-band "low/high" EQ. The treble and bass pots control the relative levels (at a linear slope) of a high-pass filter and a low-pass filter. The "EQ level" knob changes the overall strength of the filters' effect on your signal. High settings result in a mid scoop. Graphically, think of it like a capital letter M; the treble and bass knobs control whether one pointy peak of the M is taller than the other, and the EQ level knob controls the overall height of the M. Basically I think this is a bad idea and the designer needs to be slapped.
EHX has earned a terrible rep over the years for their quality control. Usually their newer pedals in the cast-aluminum housings are built pretty well, but with this one the XLR jack was not screwed to the housing, and didn't even have threads for the screws, so I had to mod it slightly to attach the jack to the case. The other parts are solid and decent quality. There's one bizarre technical quirk: when you plug an unbalanced plug into the 1/4" output jack, it automatically makes the DI output unbalanced as well. That kind of design is just not rational or sane; if it were my company, I would fire whoever thought that one up. The body is bigger than the Barber or Diamond size, but not as big as the Markbass. It runs on standard Boss-type 9VDC, and the footswitch is true bypass. In case it's not clear, I am saying do not buy this stupid, badly-designed pedal.