AC adaptor camera make LED flickering
My recommendation would be to put a large capacitor (>6800uF, perhaps) across the output of your AC-DC adapter. The flickering is due to the "ripple" which is left over after the rectification of the transformer output. 



As seen in the image, the capacitor charges while the voltage of the rectified sine wave increases, and slowly discharges as the voltage decreases. The amount the capacitor discharges as the voltage decreases determines the amount of ripple (measured in volts). Increasing the capacitor size on the output reduces the output ripple. Just remember that the more current your circuit draws, the faster the capacitor will discharge during the voltage decrease, the larger the ripple will be, and the more your LEDs will flicker.

EDIT: After re-reading your question you say that the flicker gets worse as you bring your cord closer the flicker gets worse. This suggests that you're getting some interference from the mains. Shielded cable will help block electrostatic discharges and some electromagnetic interference, but not all of it. The EM field surrounding your power cord is inducing a fluctuating current in your DC circuit. Your best bet would be to keep the cord as far away from the setup as possible, as well as using a large capacitor on the output of your adapter (as mentioned before).