A Delay plugin. It stores and then repeats the input.
Without adjusting the W/D of the effect, it will just delay the input by the given amount without letting through any of the original signal. Adjust how much W/D is applied to achieve the desired effect.
X/Y Grid
DELAY: Y axis of grid, adjusts time between signal repetitions.
FDBK: X axis of grid, adjusts amount of signal repetitions.