Well, for the most part it's becuase they are very expensive. Many will get another brand of high quality mic pre has more features and cost less. The GML is first rate great stuff. The GML stuff would be considered non-colored.

The GML preamps are the cleanest, least-colored preamps I've ever used (at least that's the way I heard them). Their EQ was the same...when I was using it I had to continually hit the "bypass" button to make sure it was really engaged, as I didn't hear all of those artifacts that you typically hear with an equalizer. It's not cheap, and if you like preamps with a "sound" these aren't the ones for you, but if you really want to hear the sound of the microphone you're using, or the sound of the source, they'd be a great choice. If I had a pair I'd probably use them on overheads (I like more colorful preamps on the individual drums and room microphones), acoustic instruments, and maybe vocals if I wanted a really clean sound. I'd imagine they'd work very well on ensemble recording as well, although I didn't have the chance to try them out that way.

-Duardo