While this Little IMP does boost the volume some (about 50% over a plain XLR to 1/4 adapter), it is not an equal to the direct XLR jack. I use a Shure SM58 (most common quality vocal mic) and I must boost the volume (again, about 50% higher than the direct XLR mic) and adjust the EQ to equal the settings of my direct XLR mic hook-up. For optimal vocals using low-impedience, it's best to find a board / PA amp that will provide all of the XLR inputs you will require.

It does exactly what it says it does, and doesn't compromise the quality of the signal or add anything to it. It doesn't work with condenser/phantom-powered mics.

This little device really makes a mic with an XLR cable sound superb. It really boosts the signal. And the other great part is, if you DO happen to get an XLR input instead of a 1/4" jack, you can simply remove the Little IMP and you're good to go. It plugs in fine although it's kind of large (same diameter as XLR, just kind of long). Overall, great device! Get one, just in case you only have a 1/4" input to plug into.