Ok I am trying to do this headphone amp HeadWize - Project: A Class A MOSFET Headphone Driver by Greg J. Szekeres i already have all the parts, the thing is that i am very confused in the top part where it says 9-15VDC, if I am correct that is the + terminal, but where is the negative one. or...

Hi everyone, yesterday I had the opportunity to attend to a little concert that the college I attend was hosting. And for the first time in my life I heard live a bagpipe composition(I don't exactly know what type of bagpipe it was), I was truly amazed of how good it sounded. So does anyone know...