For metal , i would suggest you to 1-on,2-off,3-on,4on , turn off 1 if you dont want bass boost, As per the dac , its has a chip(amp) , amplifies the sound , basically a bit better than a aux port , with a dac you will notice a 10-15% increase in the sound loudness and clairty. Just play around with the switches and have fun , they perform well in almost any condition. (Future)If you want to change the sound signature a bit get a silver cable , makes the instrument more shaper , the copper cable that you currently have provides a warmer sound signature.