The C. Crane FM Transmitter II takes a signal from an audio source such as an iPod, CD player or computer, and broadcasts it in FM, where it can be picked up by any FM radio within its range of up to 100-feet.
That simple description belies its versatility. I use it as a poor man’s Sonos: I broadcast music and podcasts from my computer to any radio in the house. I am not limited in the devices I use to hear the broadcast; I use a few Boston Acoustics Solo tabletop radios, but any radio would work, even a walkman-type device. Setup is fool-proof; just tune the radio to the proper frequency. Other people use it to watch movies without disturbing other people in the room. They just use an FM radio like the one in many iPods, and earbuds. Musicians use them for stage performance. Etc.
But there are other FM transmitters. This one stands out in a few ways. It has excellent audio quality, as good as you can get with FM. That is especially apparent in the bass frequencies. The limiting factor for your sound will almost certainly be your receiving radio or earbuds.
You can choose any broadcast frequency from 88.3 to 107.7 MHz, so are nearly guaranteed to find a clear frequency for your location. (The “digital” in the name refers to the digital display of the transmitting frequency, nothing else).
It has adjustable gain, so it will amplify even weak signals to the maximum it can handle (an LED indicator tells you when you are overloading it). It runs off AA batteries or its own wall transformer.
It can be very easily modified (by opening the case and turning a little knob) to increase its power dramatically. You can easily find instructions on the web. This is strongly recommended; the only critical reviews are from people who were disappointed with is range out of the box. That is caused by FCC regulations that limit the power allowed in all such devices. The modification will violate those regulations of course, but drastically increase the transmitter’s range.
It is cheap. Truly comparable transmitters cost a few hundred dollars. The version II is cheaper and has better audio quality than the original. And C. Crane occasionally has one that has been returned for even less.
There is basically nothing wrong with this device, and there is nothing better for the price.