The Rolls MB15b ProMatch is an inexpensive line level audio device that converts consumer level stereo RCA signals to balanced XLR professional line level signals, and vice versa. The unit is useful for video duplication and audio recording studio applications; for example, connecting a consumer VCR to a professional video deck, or an off-the-shelf CD player to a professional mixing console or recorder.

The MB15b ProMatch has 2 XLR inputs and stereo RCA outputs on one side, labeled 1, and stereo RCA inputs and 2 XLR outputs on the other side, labeled 2. Each side has stereo level controls, and an LED indicates that power is applied to the unit.

Additionally, the unit functions as a balanced XLR line level control. By adding a stereo pair of jumper cables between the 4 RCA jacks (connecting ins to outs), the level controls may be inserted into any balanced XLR line.