Channel Master posts an informative warning:
http://www.channelmasterstore.com/TV..._p/cm-7777.htm
Your signal conditions do not call for the weak signal performance of the CM-7777. I would expect it to overload.
If your attic causes unreliable reception, as many do, don't expect any amplifier to correct the problem. If you feed an amplifier a signal mixed with interference, noise and distortion, it will amplify the signal
and interference, noise and distortion.
Try reception with no amplifier. At first, with just the antenna connected to one TV using a cable no longer than 50'. If you don't get reliable reception with this test setup, odds are poor that an amplifier will make much difference.
Until you have a usable signal from the antenna, you need to consider alternate placement and/or a different antenna. Antenna location (including height) is often far more important than any other single factor.
If you actually prove the need for an amplifier, it will need to be able to handle strong signals. Consider the CM-3410 or RCA TVPRAMP1R.