Henry Engineering's The Matchbox is a two impedance converter. It's designed for use in the studio where you might need to convert a lower impedance or vice versa. It's the older version of the Matchbox, as there is also a Matchbox HD which is the newest version of this. I've used both and they are pretty much the same more or less. It's got stereo balanced XLR inputs and outputs as well as unbalanced stereo RCA connections for input and output as well. The studio that I work at now has this original Matchbox as an impedance converter for using with iPods and computers. We have an 1/8" connection going to the XLR inputs on this and it makes for easy connecting of your iPod, computer, phone, etc for listening through the monitors. It's a nice and easy way to have this available for clients who might want to check something out from an outside source. We have this permanently hooked up in this fashion, but of course the Matchbox is useful for beyond just this and can be used for converting the impedance of any signal. Once you make your connections with the Matchbox, you're good to go as there aren't any parameters or anything to mess with - it does the job more or less for you once you decide what you'd like to do with it. It's not too expensive, although I don't know exactly how it compares to the newer Matchbox HD in terms of price. I'd say you can go with either of them as they seem pretty interchangeable to me with the Matchbox HD just being a slightly updated and newer version. Either way, The Matchbox is the perfect tool for impedance conversion in any situation and is definitely something that studio owners should be aware of.