Hello All I've bought a few of these over the years, how frustrating when your mixer has two XLR inputs and you have three mics !!! Well this transformer can be used to convert an XLR balanced mic to work on a line in. There are two ways of doing it but you have to have some electronics Knowledge. Firstly you can fit it in a small metal box, this method is great if you want to have more than one channel. The other method uses an XLR to Jack converter, I found one that you could take take to bits and fit the transformer inside but I had to remove the solid fitted jack plug and use a flying cable with a jack plug on the end. If you or a friend have some basic electronics knowledge this is fairly easy to do and the results are excellent but be warned using method two the transformer is a very tight fit !!! Good luck