I recently bought an Optoma H30 and I'm very pleased with the quality of the image. However I've got a mysterious problem. The first unit that I picked up started buzzing very loudly (it's in a room upstairs and you could hear it from downstairs!). I contacted Sevenoaks who supplied the unit and they said that they would get Optoma to send a replacement unit and in the meantime I could borrow their demo unit. When I got this unit home it had exactly the same problem. Sometimes the buzzing will stop or at least get a bit quiter after the projector has been on an hour or so, but it usually starts again at some stage. The wierd thing is that neither unit has this problem at the dealers (I have checked them myself there). I have plugged the unit in via a filtered socket, but this makes no difference. The problem does not seem to be related to any other appliance that is plugged in in the house. Unless I can sort this out the unit will have to go back. But if there is a problem with the power supply or something else in my house I imagine I may have the same problem with a different make/model. Has anyone come across this problem before or got any suggestions?