Cd/dvd Stereo Head Unit Turning On And Off When I Hit Brake?help!

[pete rock]

hi everyone i have a question for the experts.i recently purchased a valor dd-858w. wired it up and everything looked fine powered up, sound from the speakers.when i went to drive with the radio on i hit the brake and the stereo turned off and then back on.this happened off and on when i hit the brakes.what could cause this to happen.i also didnt wire up the parking brake since im not worried about watching dvds.but would this cause this problem??does anyone have any advice on what this problem could be.any and all help would be greatly appreciated