This product is useful *exclusively* for the following setups:
1. Using a microphone and headphones only. (you have no speakers)
2. Using a guitar and speakers, maybe, if some feedback is acceptable. (probably not)
3. Using speakers with volume/power controls on the front. (rare - and inconvenient)
For any other use case, this product is useless, because the line and headphone outputs, although they are physically separate plugs, are actually the same output - that means, if you have speakers and headphones plugged in, you can't play back and record at the same time, as there is no way to mute the speakers.
Confusing product with very few, very niche use cases - it's not at all what the front panel makes it look like. I made a mistake buying this, but I honestly don't know who needs this or what for.