Repeat an audio signal after a set delay. Delay times run from 10 ms to 2000 ms, and feedback decides whether you get one repeat or a decaying series.
Delay time and feedback
Delay time is the gap between the source and its first repeat. Feedback is how much of each repeat is sent back into the line to become the next one.
- Feedback at 0 gives exactly one repeat. Short times of 60 ms to 120 ms produce slapback, which thickens a voice or guitar without sounding like a separate effect.
- Feedback around 30% to 50% gives a handful of audible repeats that fall away naturally.
- Feedback at 90% produces a long series that takes many seconds to fade.
Times under about 30 ms stop being heard as repeats and start colouring the tone instead, since the delayed copy interferes with the original.
Ping-pong
Ping-pong routes each repeat into the next channel rather than back into its own, so echoes alternate across the stereo field. It needs at least two channels; on a mono file the routing has nowhere to go and the effect behaves like the standard feedback path.
The alternation lands one delay period after you switch it on, because the change has to travel through the line before it reaches the output.
Changing the delay time during playback
The read position glides toward a new delay time instead of jumping to it, which is how tape delays behave and why a moving delay time bends pitch.
That glide is rate-limited. Left unbounded, moving the slider from 10 ms to 2000 ms would drag the read head backwards through the line at more than twenty times playback speed, which tears rather than sweeps. Capping it holds the repeats between half and one-and-a-half speed, so a large change takes a few seconds to arrive and stays musical the whole way.
Toggling ping-pong crossfades rather than switching. The routing change reaches the output one delay period later, when the affected repeat comes back around, and blending it in means that repeat arrives without a step in level.
None of this reaches the exported file. A render starts from the settings in place and never changes them partway, so the delay time you set is the delay time you get.
Repeats past the end of the source
The export keeps rendering after the last sample of the source until the remaining echoes drop below -60 dB, so the file ends with the repeats intact rather than cutting them off. Long delay times combined with high feedback are capped at 12 seconds of tail.
Playback works differently and stops when the source stops, so the preview does not ring on the way the exported file does.