> 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".  

<figure><img src="/files/hxXl2qKwAbSTuMOirzwF" alt=""><figcaption></figcaption></figure>

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. &#x20;

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.

<figure><img src="/files/jfCth4ALQzSabXFn8gT4" alt=""><figcaption></figcaption></figure>

Notice that the "FB In" block has a white outline indicating that it has a control panel. &#x20;

<figure><img src="/files/SYYO5cJhl7pMhEjc5Xre" alt=""><figcaption></figcaption></figure>

| Parameter | Description                     | Range          |
| --------- | ------------------------------- | -------------- |
| Gain      | Multiplies the incoming sample. | -1.90 -> +1.90 |

The functional source code for both blocks is at the links below.

{% embed url="<https://github.com/HolyCityAudio/SpinCAD-Designer/blob/master/src/com/holycityaudio/SpinCAD/CADBlocks/FBInputCADBlock.java>" %}

{% embed url="<https://github.com/HolyCityAudio/SpinCAD-Designer/blob/master/src/com/holycityaudio/SpinCAD/CADBlocks/FBOutputCADBlock.java>" %}