Caution! This is not a stereo adapter, it just mixes the left and right channel to a single mono channel.
The problem with the low volume and the high background noise is based on the nature of symmetric inputs of the recorder or audio interface in other cases: in symmetric (or balanced) audio connections there are two signal lines per channel, one carrying the original signal, the other one the inverted signal. They are also called “hot” and “cold”, or “+” and “-” on XLR. One of the signals gets inverted and mixed with the other signal, thus minimizing signal interference like hum.
If you plug a (pseudo) stereo signal into a symmetric input, the left and right stereo signals cancel each other out, and all that’s left is some low signal and a lot of noise.
If you want stereo recording, you’ll have to use a stereo jack to 2x mono jack Y-adaptor and use two inputs of your recording device.
And I should probably pay attention to what is being output and how signals are handled by my recording device (zoom h6 in my case). Haha.