Levels question for us poor home recorder people

[JWhis]

I find myself running into this problem more frequently lately - this is for those of us without a control room and an engineer or friend to help us.

I am recording in a small room, mic'ing an acoustic guitar with SM57. It is going through a Crate 10-channel mixer which I use as a preamp, out of that and into the soundcard. Obviously I can't monitor the levels through my monitors or it will feedback and cause problems. So I have on my headphones, get a great sound through them, play through a test track, and when I play it back, it is much quieter/tinnier/different sounding (still through the headphones, not switching to monitors for EQ or anything like that) than when I was monitoring it originally. The level meter seems fine when I am monitoring/recording it. Any clue what could be causing this? Even if I bump up the level of the waveform, the tonal quality is different. Is the soundcard boosting the signal somewhere between the line in and my headphones that I am not aware of? How can I get what I hear in my headphones to more or less match what is being recorded?

[JWhis]

Well update, I think I've gone a long way toward solving this one. Turns out when I moved and set up my stuff, I ran my signals through the mic in and not the line in. This seems to have helped a lot switching it back to the line in.