The stereo echo is an extension of other basic effects like the feed-forward echo and feed-back echo. The stereo version of these echo effects has different delay times for the left and right channels. This creates the perceptual impression the echo repetitions are happening at different places across the stereo field.
To create the stereo echo, at least two delay blocks are required. The effect can also be much more complicated, similar to the multi-tap echo where each delay is panned to a unique position.
A special type of stereo echo is the ping-pong echo. This effect has a specific repeated pattern of echoes bouncing back and forth from side to side. The delays alternate on the left and right sides of the stereo field.
To create the ping-pong echo, one delay block is used for the left channel and one delay block is used for the right channel. In addition to routing the output of each delay block to the respective channel, the output of one block is routed to the input of the other block, and vice versa. This will create feed-back for the repeated pattern of delays. The decay of the repetitions can be controlled by a feed-back gain, .
Next, let’s look a generalized way to implement many types of echo effects is based on a measurement called an impulse response.