Signal selector with a Raspberry Pi Music Player, a DIY guide (Part 1 of 2)

This is a DIY guide of an audio accessory, which has a 4-to-1 signal selector and a Raspberry Pi 4b. R.Pi either plays any internal media files, or receives a stream such as Airplay or bluetooth from an external mobile device. With a Pi, the setup became a very powerful, versatile and very high-quality audio source device on its own. A device such as this will make a nice addition to any home-made power amplifiers, which are often out of luck in terms of features.
This is the part 1 of a series of 2. Here, I covered the concept of the project, and made tests on key components. These are covered in the following order:

1. 4-to-1 signal switch, a DIY kit
My video: https://youtu.be/FJYAjjtZnks
Seller’s link: https://www.aliexpress.com/item/4000135053170.html?spm=2114.13010708.0.0.3a994c4dpxncYO

2. Raspberry Pi 4b

3. I2S DAC module
My video: https://youtu.be/1T9PKLeBDFc
Seller’s link: https://www.aliexpress.com/item/4000049731410.html?spm=2114.13010708.0.0.3a994c4dZQEARw

4. A switch with an LED indicator
Seller’s link: https://www.aliexpress.com/item/32996979644.html?spm=2114.13010708.0.0.3a994c4dLGA1jd

5. AC-to-DC Power supply
Seller’s link: https://www.aliexpress.com/item/4000067811811.html?spm=2114.13010708.0.0.3a994c4dLGA1jd

Please note that I have added links for many of the items above: I have already published in-depth video on the components and I recommend you to visit them as necessary. In this particular video, I only covered the basic explanation and handling of these items.
Also, please check out the video below, where I demonstrated skills for crimp connectors. This will be greatly helpful for electronic projects such as this.

Making connectors with a Crimping tool
https://youtu.be/kzxBVLyWrfI

Видео Signal selector with a Raspberry Pi Music Player, a DIY guide (Part 1 of 2) канала TinkerBox