Galaxy S5 Active (also known as SM-G870A) doesn't need root, just install Boldbeast Recorder and go.
Please use following settings to record calls:
- Record Mode: 4 or 1
- Tune Samsung 1: Yes
- Tune Samsung 2: Yes
- Tune Samsung 3: Enable Group 1
- Tune Audio Route: Group3
It records calls clearly and loudly in two sides.