mh ballast w/ hps bulb?

i bought an mh bulb with ballast from htgsupply.com, i was wondering that if i need to buy a different ballast for hps bulb, i am not going for the sea of green because my house is old and wirings are old so the breaker will give out. just wondering if i could just switch bulbs or would i need to buy a hps ballast?

certain ballasts are switchable but if it doesnt say that it is you will need a different ballast. there are certain light systems that are blue light enhanced and are good for veg and flower. personally IMO MH is only good for veg. you can flower under the MH but the HPS will probably make you happier. personally i veg under cool white cfls to keep the heat down and save on electricty and flower under my 600w HPS for those dense buds. that MH runs to hot and uses to much electricty IMO. although, some people swear by the MH for veg and flower. but if its a MH ballast im pretty sure the hps bulb isnt going to work and even if it did i dont think it would be a good idea to use it unless the system says you can. peace.

You need a conversion lamp/bulb.

hps conversion bulb is what you need for a mh system.Discount Hydroponics - Hortilux HPS Conversion Bulbs

There has been a thread or two about the diff only being the cap on the HPS ballasts. (MH supposedly don't have the cap and the switchables ballasts just bypass the cap)