Car Stereo Line Input - Pre-assembled - Headphone Output Line Input Step-up Transformer Kit

This is the Headphone Output Line Input Step-Up Transformer Kit from Akizuki Denshi.
I purchased and built this kit with the intention of using 4 circuits and 4 outputs, but due to a change in my design, I have extra units available.
Operation has been confirmed and is in good working order.

Akizuki Denshi Kit
Description:
Have you ever experienced issues with the volume being too low when connecting your smartphone or portable music player's headphone output to your car stereo's line input, compared to other sources, or found adjusting the volume troublesome? Have you also been startled by sudden loud noises when switching sources? This kit can help in such situations. These problems occur because the voltage of the headphone output is lower than the voltage required for line input. This kit uses a transformer to step up the voltage, reducing the volume difference with other sources. By not requiring a power supply, it eliminates concerns about battery degradation in your car and simplifies wiring. The input and output are isolated, which also helps with insulating connected devices. It is also effective as a ground loop isolator.

This product is intended for those who have a good understanding of electronics.
Due to the nature of the product, please understand that it is sold as-is with no returns or exchanges (NCNR).