And it also has an igniter.....that humming is the bulb sayin "Whose Got a match"!!! LOL..."BIG BANG"....huuuuuhhh huhhh!Its called a Mogul socket and needs a ballast wired to it to fire the light. Visit your local hydro shop and look around. VV
just curious..... i have a 400 watt hps, why do we need the ballast exactly? and why does it make a humming sound? what does the ballast do ?