How to DIY Car Audio Isolator with BA3121?

In the previous article, "How to DIY Car Audio Isolator for RCA Interference?" a Siemens POM alloy isolator was used to create a four-channel car audio isolator due to noise issues after reducing the Android navigation to low-level PCA. While the noise was eliminated after installation, the soundstage narrowed slightly and the bass strength diminished. To address these issues, this article will guide you through creating a second isolator using the BA3121 solution, which resolves the problems effectively without affecting sound quality.

Firstly, you'll need materials similar to those used in the previous article—eight pure copper gold-plated RCA female connectors.

This time, you'll also need a silver-colored aluminum enclosure. Since the board's height isn't as tall as the previous one, a box with a height of 26.5mm will suffice. Position and drill holes according to the dimensions.

The holes should be 11mm in diameter. If your drill bit isn't that large, you can use a small file to gradually enlarge the holes.

Install the RCA female connectors.

Use silver-plated wire for connections. The module uses a BA3121 board, which requires a 12V power supply. A DVD disc was used between the board and the aluminum enclosure, cut into a rectangular shape and secured with 3M double-sided tape.

Compare the finished product with the one made in the previous article.

After testing in the car, it was found that connecting to the output caused noise. However, when the board was powered by a startup power source, there was no noise. This indicates that the problem might be related to the power supply. A dedicated isolation power board was then prepared.

After powering the BA3121 with this isolation power board, the car's speakers had no noise, and the sound quality remained intact, successfully resolving the issue.