> For the complete documentation index, see [llms.txt](https://holy-city-audio.gitbook.io/spincad-designer/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://holy-city-audio.gitbook.io/spincad-designer/menus/loop.md).
# Loop
The Loop Menu has just one entry, "Add".
It is a special case programming wise in that it drops in two blocks - a Loop Input and a Loop Output. These blocks are used to reliably make a feedback loop in your design. They introduce 1 sample of delay.
When you first drop in these blocks, your mouse pointer will be moving the "FB Out" block. Click to drop this in place and continue editing.
Notice that the "FB In" block has a white outline indicating that it has a control panel.
| Parameter | Description | Range |
| --------- | ------------------------------- | -------------- |
| Gain | Multiplies the incoming sample. | -1.90 -> +1.90 |
The functional source code for both blocks is at the links below.
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