I like the enclosed ballast. They have a cheaper one at atlantalightbulbs but its not in an enclosure. How noisy is this unit? Its worth the extra money if its quiet.

Please advise.

Other than the click it makes when it ignites the lamp, mine makes no noise that my ears can hear. I have the original Chinese e-ballast.

Sounds promising. Now its a tossup between the S400DD lamp and the Osram HTI152W. I like the small arc of the osram. With a good reflector it would yield a high % useable flux. Too bad its twice the price and much less lumens

Please link the ballast you're referring to. 'Not in an enclosure' doesn't sound like an e-ballast. That sounds like a regular coil ballast to me.

Ballasts are divided into magnetic and electronic. Magnetic ballasts are basically huge transformers + capacitors, while electronic ballasts are much cooler running heatsunk boxes with active components inside.

Magnetic ballasts have the potential to hum at 60hz, and run very hot compared to electronic ballasts. Electronic ballasts are generally much more expensive, though the Lumenlabs one is a bargain compared to anything I could find for sale on the intarweb. The cheapest mag ballasts are $40-$50 or so with a big shipping fee (wire wrapped around iron coils ain't light).