I've just completed assembly of my tuner kit and am having the exact same problem. The tuner is functioning; it powers up and I can seek both on the AM & FM band. It will lock on the local stations no problem, but the audio level is almost non-existant. I'm not an audio or electronics engineer by any means, but I dare say it sounds similar to trying what you'd hear when trying to drive a small speaker with an unamplified (line level) signal.

Any more thoughts out there?

-Randy