My wife bought some multi-color LED Christmas-light strings, 50 lights for $10 per string. We used them to decorate our traditional wreath over the door, but I was disappointed with their brightness. Checking them on the bench, I found that having no bridge rectifier, they operated on only one half of the AC line cycle, and with 50 LEDs in series, they needed 125 to 135 volts to draw a even modest 10mA current.** Their conduction angle was also less than one might like.
BTW, half-cycle operation makes a 50 or 60Hz flicker, not a 25 or 30Hz flicker as many web-sites state.
Clearly, adding a bridge rectifier would double both the LED's flicker rate, and light output. But I elected to add a storage capacitor after the bridge (200uF, for 2 to 3 strings), and feed the LED string with DC. This would make the conduction angle 100%, and further increase the light output.
My in-situ measurements: 162 volts and 42mA per string, about 5x the original estimated current. Yep, they looked about five times brighter. At least that's what I told my wife, after she said they didn't look _that_ much brighter.
** The string has 20 yellow LEDs, and 10 each red, green and blue. I guess the band-gap voltages add up to ~ 110V.