The equaliser can give an increase in volume, but it's very easy to introduce distortion like that. With any equaliser used with a hifi, it's better to aim for "unity gain", where the volume is the same with the eq in or out. Thus you'd normally adjust for that, if necessary, after changing the frequency curve.
You could give it a try as a volume boost and check how much headroom there is before distortion, but do it very gradually. If you are happy with the sound quality without the eq, you could just raise all the sliders by the same amount to increase the volume. Otherwise vary the relative slider settings till it makes everything you play sound a little bit better.
The alternative solution to your issue would be to connect a headphone amp to the B2's line out. Many of them combine an amp and DAC, which could improve the sound quality as well as the volume and there's no risk of distortion.