The signal booster requires a stereo plug -- in fact, you get a little piece of paper with a warning message about this when you purchase the booster.

This doesn't mean that your recorded music needs to be stereo -- just the plug. 95% of the square dance music I use is mono.

Personally, I've had trouble with the signal booster. The knob is flaky or some connection is bad. It's been fixed once by Jim Henshel, but it still doesn't work particularly well. Sometimes I have to wiggle it or fiddle the knob to get it working. I purchased a backup signal booster which is still in its original plastic bag -- just in case mine decides to expire competely.

I've heard of other callers who have also had problems with their signal booster. One caller had some other contraption that was either purchased at or made from parts from Radio Shack. This caller was bragging that it only cost him about $10 instead of the $40 for the signal booster.

I think the MA-150 is wonderful. I fully recommend it. It's more powerful, smaller, and easier to use. And it doesn't require that stupid little signal booster! In my opinion, the sound from the MA-150 is better than the sound from the 75B.

The only drawback about the MA-150 is that vinyl records can no longer be used.